HAProxy
Configuration Manual
version 1.5-dev18-47
willy tarreau
2013/04/03
This document covers the configuration language as implemented in the version
specified above. It does not provide any hint, example or advice. For such
documentation, please refer to the Reference Manual or the Architecture Manual.
The summary below is meant to help you search sections by name and navigate
through the document.
Note to documentation contributors :
This document is formatted with 80 columns per line, with even number of
spaces for indentation and without tabs. Please follow these rules strictly
so that it remains easily printable everywhere. If a line needs to be
printed verbatim and does not fit, please end each line with a backslash
('\') and continue on next line, indented by two characters. It is also
sometimes useful to prefix all output lines (logs, console outs) with 3
closing angle brackets ('>>>') in order to help get the difference between
inputs and outputs when it can become ambiguous. If you add sections,
please update the summary below for easier searching.Summary
1.2.
1.2.1.
1.2.2.
1.3.
1.3.1.
1.3.2.
2.2.
2.3.
3.2.
3.3.
3.4.
3.5.
4.
5.1.
7.1.
7.2.
7.5.2.
7.5.3.
7.6.
7.8.
8.
8.1.
8.2.
8.2.1.
8.2.2.
8.2.3.
8.2.4.
8.2.5.
8.4.
8.9.
9.1.
9.2.
1. Quick reminder about HTTP
When haproxy is running in HTTP mode, both the request and the response are fully analyzed and indexed, thus it becomes possible to build matching criteria on almost anything found in the contents. However, it is important to understand how HTTP requests and responses are formed, and how HAProxy decomposes them. It will then become easier to write correct rules and to debug existing configurations.
1.1. The HTTP transaction model
The HTTP protocol is transaction-driven. This means that each request will lead to one and only one response. Traditionally, a TCP connection is established from the client to the server, a request is sent by the client on the connection, the server responds and the connection is closed. A new request will involve a new connection : [CON1] [REQ1] ... [RESP1] [CLO1] [CON2] [REQ2] ... [RESP2] [CLO2] ... In this mode, called the "HTTP close" mode, there are as many connection establishments as there are HTTP transactions. Since the connection is closed by the server after the response, the client does not need to know the content length. Due to the transactional nature of the protocol, it was possible to improve it to avoid closing a connection between two subsequent transactions. In this mode however, it is mandatory that the server indicates the content length for each response so that the client does not wait indefinitely. For this, a special header is used: "Content-length". This mode is called the "keep-alive" mode : [CON] [REQ1] ... [RESP1] [REQ2] ... [RESP2] [CLO] ... Its advantages are a reduced latency between transactions, and less processing power required on the server side. It is generally better than the close mode, but not always because the clients often limit their concurrent connections to a smaller value. A last improvement in the communications is the pipelining mode. It still uses keep-alive, but the client does not wait for the first response to send the second request. This is useful for fetching large number of images composing a page : [CON] [REQ1] [REQ2] ... [RESP1] [RESP2] [CLO] ... This can obviously have a tremendous benefit on performance because the network latency is eliminated between subsequent requests. Many HTTP agents do not correctly support pipelining since there is no way to associate a response with the corresponding request in HTTP. For this reason, it is mandatory for the server to reply in the exact same order as the requests were received. By default HAProxy operates in a tunnel-like mode with regards to persistent connections: for each connection it processes the first request and forwards everything else (including additional requests) to selected server. Once established, the connection is persisted both on the client and server sides. Use "option http-server-close" to preserve client persistent connections while handling every incoming request individually, dispatching them one after another to servers, in HTTP close mode. Use "option httpclose" to switch both sides to HTTP close mode. "option forceclose" and "option http-pretend-keepalive" help working around servers misbehaving in HTTP close mode.
1.2. HTTP request
First, let's consider this HTTP request :
Line Contents
number
1 GET /serv/login.php?lang=en&profile=2 HTTP/1.1
2 Host: www.mydomain.com
3 User-agent: my small browser
4 Accept: image/jpeg, image/gif
5 Accept: image/png1.2.1. The Request line
Line 1 is the "request line". It is always composed of 3 fields :
- a METHOD : GET
- a URI : /serv/login.php?lang=en&profile=2
- a version tag : HTTP/1.1
All of them are delimited by what the standard calls LWS (linear white spaces),
which are commonly spaces, but can also be tabs or line feeds/carriage returns
followed by spaces/tabs. The method itself cannot contain any colon (':') and
is limited to alphabetic letters. All those various combinations make it
desirable that HAProxy performs the splitting itself rather than leaving it to
the user to write a complex or inaccurate regular expression.
The URI itself can have several forms :
- A "relative URI" :
/serv/login.php?lang=en&profile=2
It is a complete URL without the host part. This is generally what is
received by servers, reverse proxies and transparent proxies.
- An "absolute URI", also called a "URL" :
http://192.168.0.12:8080/serv/login.php?lang=en&profile=2
It is composed of a "scheme" (the protocol name followed by '://'), a host
name or address, optionally a colon (':') followed by a port number, then
a relative URI beginning at the first slash ('/') after the address part.
This is generally what proxies receive, but a server supporting HTTP/1.1
must accept this form too.
- a star ('*') : this form is only accepted in association with the OPTIONS
method and is not relayable. It is used to inquiry a next hop's
capabilities.
- an address:port combination : 192.168.0.12:80
This is used with the CONNECT method, which is used to establish TCP
tunnels through HTTP proxies, generally for HTTPS, but sometimes for
other protocols too.
In a relative URI, two sub-parts are identified. The part before the question
mark is called the "path". It is typically the relative path to static objects
on the server. The part after the question mark is called the "query string".
It is mostly used with GET requests sent to dynamic scripts and is very
specific to the language, framework or application in use.1.2.2. The request headers
The headers start at the second line. They are composed of a name at the
beginning of the line, immediately followed by a colon (':'). Traditionally,
an LWS is added after the colon but that's not required. Then come the values.
Multiple identical headers may be folded into one single line, delimiting the
values with commas, provided that their order is respected. This is commonly
encountered in the "Cookie:" field. A header may span over multiple lines if
the subsequent lines begin with an LWS. In the example in 1.2, lines 4 and 5
define a total of 3 values for the "Accept:" header.
Contrary to a common mis-conception, header names are not case-sensitive, and
their values are not either if they refer to other header names (such as the
"Connection:" header).
The end of the headers is indicated by the first empty line. People often say
that it's a double line feed, which is not exact, even if a double line feed
is one valid form of empty line.
Fortunately, HAProxy takes care of all these complex combinations when indexing
headers, checking values and counting them, so there is no reason to worry
about the way they could be written, but it is important not to accuse an
application of being buggy if it does unusual, valid things.
Important note:
As suggested by RFC2616, HAProxy normalizes headers by replacing line breaks
in the middle of headers by LWS in order to join multi-line headers. This
is necessary for proper analysis and helps less capable HTTP parsers to work
correctly and not to be fooled by such complex constructs.1.3. HTTP response
An HTTP response looks very much like an HTTP request. Both are called HTTP
messages. Let's consider this HTTP response :
Line Contents
number
1 HTTP/1.1 200 OK
2 Content-length: 350
3 Content-Type: text/html
As a special case, HTTP supports so called "Informational responses" as status
codes 1xx. These messages are special in that they don't convey any part of the
response, they're just used as sort of a signaling message to ask a client to
continue to post its request for instance. In the case of a status 100 response
the requested information will be carried by the next non-100 response message
following the informational one. This implies that multiple responses may be
sent to a single request, and that this only works when keep-alive is enabled
(1xx messages are HTTP/1.1 only). HAProxy handles these messages and is able to
correctly forward and skip them, and only process the next non-100 response. As
such, these messages are neither logged nor transformed, unless explicitly
state otherwise. Status 101 messages indicate that the protocol is changing
over the same connection and that haproxy must switch to tunnel mode, just as
if a CONNECT had occurred. Then the Upgrade header would contain additional
information about the type of protocol the connection is switching to.1.3.1. The Response line
Line 1 is the "response line". It is always composed of 3 fields :
- a version tag : HTTP/1.1
- a status code : 200
- a reason : OK
The status code is always 3-digit. The first digit indicates a general status :
- 1xx = informational message to be skipped (eg: 100, 101)
- 2xx = OK, content is following (eg: 200, 206)
- 3xx = OK, no content following (eg: 302, 304)
- 4xx = error caused by the client (eg: 401, 403, 404)
- 5xx = error caused by the server (eg: 500, 502, 503)
Please refer to RFC2616 for the detailed meaning of all such codes. The
"reason" field is just a hint, but is not parsed by clients. Anything can be
found there, but it's a common practice to respect the well-established
messages. It can be composed of one or multiple words, such as "OK", "Found",
or "Authentication Required".
Haproxy may emit the following status codes by itself :
Code When / reason
200 access to stats page, and when replying to monitoring requests
301 when performing a redirection, depending on the configured code
302 when performing a redirection, depending on the configured code
303 when performing a redirection, depending on the configured code
307 when performing a redirection, depending on the configured code
308 when performing a redirection, depending on the configured code
400 for an invalid or too large request
401 when an authentication is required to perform the action (when
accessing the stats page)
403 when a request is forbidden by a "block" ACL or "reqdeny" filter
408 when the request timeout strikes before the request is complete
500 when haproxy encounters an unrecoverable internal error, such as a
memory allocation failure, which should never happen
502 when the server returns an empty, invalid or incomplete response, or
when an "rspdeny" filter blocks the response.
503 when no server was available to handle the request, or in response to
monitoring requests which match the "monitor fail" condition
504 when the response timeout strikes before the server responds
The error 4xx and 5xx codes above may be customized (see "errorloc" in section
4.2).1.3.2. The response headers
Response headers work exactly like request headers, and as such, HAProxy uses the same parsing function for both. Please refer to paragraph 1.2.2 for more details.
2. Configuring HAProxy
2.1. Configuration file format
HAProxy's configuration process involves 3 major sources of parameters :
- the arguments from the command-line, which always take precedence
- the "global" section, which sets process-wide parameters
- the proxies sections which can take form of "defaults", "listen",
"frontend" and "backend".
The configuration file syntax consists in lines beginning with a keyword
referenced in this manual, optionally followed by one or several parameters
delimited by spaces. If spaces have to be entered in strings, then they must be
preceded by a backslash ('\') to be escaped. Backslashes also have to be
escaped by doubling them.2.2. Time format
Some parameters involve values representing time, such as timeouts. These values are generally expressed in milliseconds (unless explicitly stated otherwise) but may be expressed in any other unit by suffixing the unit to the numeric value. It is important to consider this because it will not be repeated for every keyword. Supported units are : - us : microseconds. 1 microsecond = 1/1000000 second - ms : milliseconds. 1 millisecond = 1/1000 second. This is the default. - s : seconds. 1s = 1000ms - m : minutes. 1m = 60s = 60000ms - h : hours. 1h = 60m = 3600s = 3600000ms - d : days. 1d = 24h = 1440m = 86400s = 86400000ms
2.3. Examples
# Simple configuration for an HTTP proxy listening on port 80 on all
# interfaces and forwarding requests to a single backend "servers" with a
# single server "server1" listening on 127.0.0.1:8000
global
daemon
maxconn 256
defaults
mode http
timeout connect 5000ms
timeout client 50000ms
timeout server 50000ms
frontend http-in
bind *:80
default_backend servers
backend servers
server server1 127.0.0.1:8000 maxconn 32
# The same configuration defined with a single listen block. Shorter but
# less expressive, especially in HTTP mode.
global
daemon
maxconn 256
defaults
mode http
timeout connect 5000ms
timeout client 50000ms
timeout server 50000ms
listen http-in
bind *:80
server server1 127.0.0.1:8000 maxconn 32
Assuming haproxy is in $PATH, test these configurations in a shell with:
$ sudo haproxy -f configuration.conf -c3. Global parameters
Parameters in the "global" section are process-wide and often OS-specific. They are generally set once for all and do not need being changed once correct. Some of them have command-line equivalents. The following keywords are supported in the "global" section : * Process management and security - ca-base - chroot - crt-base - daemon - gid - group - log - log-send-hostname - nbproc - pidfile - uid - ulimit-n - user - stats - node - description - unix-bind * Performance tuning - maxconn - maxconnrate - maxcomprate - maxcompcpuusage - maxpipes - maxsslconn - noepoll - nokqueue - nopoll - nosplice - spread-checks - tune.bufsize - tune.chksize - tune.comp.maxlevel - tune.http.cookielen - tune.http.maxhdr - tune.maxaccept - tune.maxpollevents - tune.maxrewrite - tune.pipesize - tune.rcvbuf.client - tune.rcvbuf.server - tune.sndbuf.client - tune.sndbuf.server - tune.ssl.cachesize - tune.ssl.lifetime - tune.ssl.maxrecord - tune.zlib.memlevel - tune.zlib.windowsize * Debugging - debug - quiet
3.1. Process management and security
Assigns a default directory to fetch SSL CA certificates and CRLs from when a relative path is used with "ca-file" or "crl-file" directives. Absolute locations specified in "ca-file" and "crl-file" prevail and ignore "ca-base".
Changes current directory to <jail dir> and performs a chroot() there before dropping privileges. This increases the security level in case an unknown vulnerability would be exploited, since it would make it very hard for the attacker to exploit the system. This only works when the process is started with superuser privileges. It is important to ensure that <jail_dir> is both empty and unwritable to anyone.
On Linux 2.6 and above, it is possible to bind a process to a specific CPU set. This means that the process will never run on other CPUs. The "cpu-map" directive specifies CPU sets for process sets. The first argument is the process number to bind. This process must have a number between 1 and 32, and any process IDs above nbproc are ignored. It is possible to specify all processes at once using "all", only odd numbers using "odd" or even numbers using "even", just like with the "bind-process" directive. The second and forthcoming arguments are CPU sets. Each CPU set is either a unique number between 0 and 31 or a range with two such numbers delimited by a dash ('-'). Multiple CPU numbers or ranges may be specified, and the processes will be allowed to bind to all of them. Obviously, multiple "cpu-map" directives may be specified. Each "cpu-map" directive will replace the previous ones when they overlap.
Assigns a default directory to fetch SSL certificates from when a relative path is used with "crtfile" directives. Absolute locations specified after "crtfile" prevail and ignore "crt-base".
Makes the process fork into background. This is the recommended mode of operation. It is equivalent to the command line "-D" argument. It can be disabled by the command line "-db" argument.
Changes the process' group ID to <number>. It is recommended that the group ID is dedicated to HAProxy or to a small set of similar daemons. HAProxy must be started with a user belonging to this group, or with superuser privileges. Note that if haproxy is started from a user having supplementary groups, it will only be able to drop these groups if started with superuser privileges. See also "group" and "uid".
Similar to "gid" but uses the GID of group name <group name> from /etc/group. See also "gid" and "user".
Adds a global syslog server. Up to two global servers can be defined. They will receive logs for startups and exits, as well as all logs from proxies configured with "log global". <address> can be one of: - An IPv4 address optionally followed by a colon and a UDP port. If no port is specified, 514 is used by default (the standard syslog port). - An IPv6 address followed by a colon and optionally a UDP port. If no port is specified, 514 is used by default (the standard syslog port). - A filesystem path to a UNIX domain socket, keeping in mind considerations for chroot (be sure the path is accessible inside the chroot) and uid/gid (be sure the path is appropriately writeable). Any part of the address string may reference any number of environment variables by preceding their name with a dollar sign ('$') and optionally enclosing them with braces ('{}'), similarly to what is done in Bourne shell. <facility> must be one of the 24 standard syslog facilities : kern user mail daemon auth syslog lpr news uucp cron auth2 ftp ntp audit alert cron2 local0 local1 local2 local3 local4 local5 local6 local7 An optional level can be specified to filter outgoing messages. By default, all messages are sent. If a maximum level is specified, only messages with a severity at least as important as this level will be sent. An optional minimum level can be specified. If it is set, logs emitted with a more severe level than this one will be capped to this level. This is used to avoid sending "emerg" messages on all terminals on some default syslog configurations. Eight levels are known : emerg alert crit err warning notice info debug
Sets the hostname field in the syslog header. If optional "string" parameter is set the header is set to the string contents, otherwise uses the hostname of the system. Generally used if one is not relaying logs through an intermediate syslog server or for simply customizing the hostname printed in the logs.
Sets the tag field in the syslog header to this string. It defaults to the program name as launched from the command line, which usually is "haproxy". Sometimes it can be useful to differentiate between multiple processes running on the same host.
Creates <number> processes when going daemon. This requires the "daemon" mode. By default, only one process is created, which is the recommended mode of operation. For systems limited to small sets of file descriptors per process, it may be needed to fork multiple daemons. USING MULTIPLE PROCESSES IS HARDER TO DEBUG AND IS REALLY DISCOURAGED. See also "daemon".
Writes pids of all daemons into file <pidfile>. This option is equivalent to the "-p" command line argument. The file must be accessible to the user starting the process. See also "daemon".
Limits the stats socket to a certain set of processes numbers. By default the stats socket is bound to all processes, causing a warning to be emitted when nbproc is greater than 1 because there is no way to select the target process when connecting. However, by using this setting, it becomes possible to pin the stats socket to a specific set of processes, typically the first one. The warning will automatically be disabled when this setting is used, whatever the number of processes used.
Binds a UNIX socket to <path> or a TCPv4/v6 address to <address:port>. Connections to this socket will return various statistics outputs and even allow some commands to be issued to change some runtime settings. Please consult section 9.2 "Unix Socket commands" for more details. All parameters supported by "bind" lines are supported, for instance to restrict access to some users or their access rights. Please consult section 5.1 for more information.
The default timeout on the stats socket is set to 10 seconds. It is possible to change this value with "stats timeout". The value must be passed in milliseconds, or be suffixed by a time unit among { us, ms, s, m, h, d }.
By default, the stats socket is limited to 10 concurrent connections. It is possible to change this value with "stats maxconn".
Changes the process' user ID to <number>. It is recommended that the user ID is dedicated to HAProxy or to a small set of similar daemons. HAProxy must be started with superuser privileges in order to be able to switch to another one. See also "gid" and "user".
Sets the maximum number of per-process file-descriptors to <number>. By default, it is automatically computed, so it is recommended not to use this option.
unix-bind [ prefix <prefix> ] [ mode <mode> ] [ user <user> ] [ uid <uid> ]
[ group <group> ] [ gid <gid> ]
Fixes common settings to UNIX listening sockets declared in "bind" statements. This is mainly used to simplify declaration of those UNIX sockets and reduce the risk of errors, since those settings are most commonly required but are also process-specific. The <prefix> setting can be used to force all socket path to be relative to that directory. This might be needed to access another component's chroot. Note that those paths are resolved before haproxy chroots itself, so they are absolute. The <mode>, <user>, <uid>, <group> and <gid> all have the same meaning as their homonyms used by the "bind" statement. If both are specified, the "bind" statement has priority, meaning that the "unix-bind" settings may be seen as process-wide default settings.
Similar to "uid" but uses the UID of user name <user name> from /etc/passwd. See also "uid" and "group".
Only letters, digits, hyphen and underscore are allowed, like in DNS names. This statement is useful in HA configurations where two or more processes or servers share the same IP address. By setting a different node-name on all nodes, it becomes easy to immediately spot what server is handling the traffic.
Add a text that describes the instance. Please note that it is required to escape certain characters (# for example) and this text is inserted into a html page so you should avoid using "<" and ">" characters.
3.2. Performance tuning
Sets the maximum per-process number of concurrent connections to <number>. It is equivalent to the command-line argument "-n". Proxies will stop accepting connections when this limit is reached. The "ulimit-n" parameter is automatically adjusted according to this value. See also "ulimit-n".
Sets the maximum per-process number of connections per second to <number>. Proxies will stop accepting connections when this limit is reached. It can be used to limit the global capacity regardless of each frontend capacity. It is important to note that this can only be used as a service protection measure, as there will not necessarily be a fair share between frontends when the limit is reached, so it's a good idea to also limit each frontend to some value close to its expected share. Also, lowering tune.maxaccept can improve fairness.
Sets the maximum per-process input compression rate to <number> kilobytes pers second. For each session, if the maximum is reached, the compression level will be decreased during the session. If the maximum is reached at the beginning of a session, the session will not compress at all. If the maximum is not reached, the compression level will be increased up to tune.comp.maxlevel. A value of zero means there is no limit, this is the default value.
Sets the maximum CPU usage HAProxy can reach before stopping the compression for new requests or decreasing the compression level of current requests. It works like 'maxcomprate' but measures CPU usage instead of incoming data bandwidth. The value is expressed in percent of the CPU used by haproxy. In case of multiple processes (nbproc > 1), each process manages its individual usage. A value of 100 disable the limit. The default value is 100. Setting a lower value will prevent the compression work from slowing the whole process down and from introducing high latencies.
Sets the maximum per-process number of pipes to <number>. Currently, pipes are only used by kernel-based tcp splicing. Since a pipe contains two file descriptors, the "ulimit-n" value will be increased accordingly. The default value is maxconn/4, which seems to be more than enough for most heavy usages. The splice code dynamically allocates and releases pipes, and can fall back to standard copy, so setting this value too low may only impact performance.
Sets the maximum per-process number of concurrent SSL connections to <number>. By default there is no SSL-specific limit, which means that the global maxconn setting will apply to all connections. Setting this limit avoids having openssl use too much memory and crash when malloc returns NULL (since it unfortunately does not reliably check for such conditions). Note that the limit applies both to incoming and outgoing connections, so one connection which is deciphered then ciphered accounts for 2 SSL connections.
Sets the maximum amount of RAM in megabytes per process usable by the zlib. When the maximum amount is reached, future sessions will not compress as long as RAM is unavailable. When sets to 0, there is no limit. The default value is 0. The value is available in bytes on the UNIX socket with "show info" on the line "MaxZlibMemUsage", the memory used by zlib is "ZlibMemUsage" in bytes.
Disables the use of the "epoll" event polling system on Linux. It is equivalent to the command-line argument "-de". The next polling system used will generally be "poll". See also "nopoll".
Disables the use of the "kqueue" event polling system on BSD. It is equivalent to the command-line argument "-dk". The next polling system used will generally be "poll". See also "nopoll".
Disables the use of the "poll" event polling system. It is equivalent to the command-line argument "-dp". The next polling system used will be "select". It should never be needed to disable "poll" since it's available on all platforms supported by HAProxy. See also "nokqueue" and "noepoll".
Disables the use of kernel tcp splicing between sockets on Linux. It is equivalent to the command line argument "-dS". Data will then be copied using conventional and more portable recv/send calls. Kernel tcp splicing is limited to some very recent instances of kernel 2.6. Most versions between 2.6.25 and 2.6.28 are buggy and will forward corrupted data, so they must not be used. This option makes it easier to globally disable kernel splicing in case of doubt. See also "option splice-auto", "option splice-request" and "option splice-response".
Sometimes it is desirable to avoid sending health checks to servers at exact intervals, for instance when many logical servers are located on the same physical server. With the help of this parameter, it becomes possible to add some randomness in the check interval between 0 and +/- 50%. A value between 2 and 5 seems to show good results. The default value remains at 0.
Sets the buffer size to this size (in bytes). Lower values allow more sessions to coexist in the same amount of RAM, and higher values allow some applications with very large cookies to work. The default value is 16384 and can be changed at build time. It is strongly recommended not to change this from the default value, as very low values will break some services such as statistics, and values larger than default size will increase memory usage, possibly causing the system to run out of memory. At least the global maxconn parameter should be decreased by the same factor as this one is increased. If HTTP request is larger than (tune.bufsize - tune.maxrewrite), haproxy will return HTTP 400 (Bad Request) error. Similarly if an HTTP response is larger than this size, haproxy will return HTTP 502 (Bad Gateway).
Sets the check buffer size to this size (in bytes). Higher values may help find string or regex patterns in very large pages, though doing so may imply more memory and CPU usage. The default value is 16384 and can be changed at build time. It is not recommended to change this value, but to use better checks whenever possible.
Sets the maximum compression level. The compression level affects CPU usage during compression. This value affects CPU usage during compression. Each session using compression initializes the compression algorithm with this value. The default value is 1.
Sets the maximum length of captured cookies. This is the maximum value that the "capture cookie xxx len yyy" will be allowed to take, and any upper value will automatically be truncated to this one. It is important not to set too high a value because all cookie captures still allocate this size whatever their configured value (they share a same pool). This value is per request per response, so the memory allocated is twice this value per connection. When not specified, the limit is set to 63 characters. It is recommended not to change this value.
Sets the maximum number of headers in a request. When a request comes with a number of headers greater than this value (including the first line), it is rejected with a "400 Bad Request" status code. Similarly, too large responses are blocked with "502 Bad Gateway". The default value is 101, which is enough for all usages, considering that the widely deployed Apache server uses the same limit. It can be useful to push this limit further to temporarily allow a buggy application to work by the time it gets fixed. Keep in mind that each new header consumes 32bits of memory for each session, so don't push this limit too high.
Sets the maximum number of consecutive connections a process may accept in a row before switching to other work. In single process mode, higher numbers give better performance at high connection rates. However in multi-process modes, keeping a bit of fairness between processes generally is better to increase performance. This value applies individually to each listener, so that the number of processes a listener is bound to is taken into account. This value defaults to 64. In multi-process mode, it is divided by twice the number of processes the listener is bound to. Setting this value to -1 completely disables the limitation. It should normally not be needed to tweak this value.
Sets the maximum amount of events that can be processed at once in a call to the polling system. The default value is adapted to the operating system. It has been noticed that reducing it below 200 tends to slightly decrease latency at the expense of network bandwidth, and increasing it above 200 tends to trade latency for slightly increased bandwidth.
Sets the reserved buffer space to this size in bytes. The reserved space is used for header rewriting or appending. The first reads on sockets will never fill more than bufsize-maxrewrite. Historically it has defaulted to half of bufsize, though that does not make much sense since there are rarely large numbers of headers to add. Setting it too high prevents processing of large requests or responses. Setting it too low prevents addition of new headers to already large requests or to POST requests. It is generally wise to set it to about 1024. It is automatically readjusted to half of bufsize if it is larger than that. This means you don't have to worry about it when changing bufsize.
Sets the kernel pipe buffer size to this size (in bytes). By default, pipes are the default size for the system. But sometimes when using TCP splicing, it can improve performance to increase pipe sizes, especially if it is suspected that pipes are not filled and that many calls to splice() are performed. This has an impact on the kernel's memory footprint, so this must not be changed if impacts are not understood.
Forces the kernel socket receive buffer size on the client or the server side to the specified value in bytes. This value applies to all TCP/HTTP frontends and backends. It should normally never be set, and the default size (0) lets the kernel autotune this value depending on the amount of available memory. However it can sometimes help to set it to very low values (eg: 4096) in order to save kernel memory by preventing it from buffering too large amounts of received data. Lower values will significantly increase CPU usage though.
Forces the kernel socket send buffer size on the client or the server side to the specified value in bytes. This value applies to all TCP/HTTP frontends and backends. It should normally never be set, and the default size (0) lets the kernel autotune this value depending on the amount of available memory. However it can sometimes help to set it to very low values (eg: 4096) in order to save kernel memory by preventing it from buffering too large amounts of received data. Lower values will significantly increase CPU usage though. Another use case is to prevent write timeouts with extremely slow clients due to the kernel waiting for a large part of the buffer to be read before notifying haproxy again.
Sets the size of the global SSL session cache, in a number of blocks. A block is large enough to contain an encoded session without peer certificate. An encoded session with peer certificate is stored in multiple blocks depending on the size of the peer certificate. A block use approximatively 200 bytes of memory. The default value may be forced at build time, otherwise defaults to 20000. When the cache is full, the most idle entries are purged and reassigned. Higher values reduce the occurrence of such a purge, hence the number of CPU-intensive SSL handshakes by ensuring that all users keep their session as long as possible. All entries are pre-allocated upon startup and are shared between all processes if "nbproc" is greater than 1. Setting this value to 0 disables the SSL session cache.
Sets how long a cached SSL session may remain valid. This time is expressed in seconds and defaults to 300 (5 mn). It is important to understand that it does not guarantee that sessions will last that long, because if the cache is full, the longest idle sessions will be purged despite their configured lifetime. The real usefulness of this setting is to prevent sessions from being used for too long.
Sets the maximum amount of bytes passed to SSL_write() at a time. Default value 0 means there is no limit. Over SSL/TLS, the client can decipher the data only once it has received a full record. With large records, it means that clients might have to download up to 16kB of data before starting to process them. Limiting the value can improve page load times on browsers located over high latency or low bandwidth networks. It is suggested to find optimal values which fit into 1 or 2 TCP segments (generally 1448 bytes over Ethernet with TCP timestamps enabled, or 1460 when timestamps are disabled), keeping in mind that SSL/TLS add some overhead. Typical values of 1419 and 2859 gave good results during tests. Use "strace -e trace=write" to find the best value.
Sets the memLevel parameter in zlib initialization for each session. It defines how much memory should be allocated for the intenal compression state. A value of 1 uses minimum memory but is slow and reduces compression ratio, a value of 9 uses maximum memory for optimal speed. Can be a value between 1 and 9. The default value is 8.
Sets the window size (the size of the history buffer) as a parameter of the zlib initialization for each session. Larger values of this parameter result in better compression at the expense of memory usage. Can be a value between 8 and 15. The default value is 15.
3.3. Debugging
Enables debug mode which dumps to stdout all exchanges, and disables forking into background. It is the equivalent of the command-line argument "-d". It should never be used in a production configuration since it may prevent full system startup.
Do not display any message during startup. It is equivalent to the command- line argument "-q".
3.4. Userlists
It is possible to control access to frontend/backend/listen sections or to http stats by allowing only authenticated and authorized users. To do this, it is required to create at least one userlist and to define users.
Creates new userlist with name <listname>. Many independent userlists can be used to store authentication & authorization data for independent customers.
Adds group <groupname> to the current userlist. It is also possible to attach users to this group by using a comma separated list of names proceeded by "users" keyword.
Adds user <username> to the current userlist. Both secure (encrypted) and insecure (unencrypted) passwords can be used. Encrypted passwords are evaluated using the crypt(3) function so depending of the system's capabilities, different algorithms are supported. For example modern Glibc based Linux system supports MD5, SHA-256, SHA-512 and of course classic, DES-based method of crypting passwords.
Example:
userlist L1
group G1 users tiger,scott
group G2 users xdb,scott
user tiger password $6$k6y3o.eP$JlKBx9za9667qe4(...)xHSwRv6J.C0/D7cV91
user scott insecure-password elgato
user xdb insecure-password hello
userlist L2
group G1
group G2
user tiger password $6$k6y3o.eP$JlKBx(...)xHSwRv6J.C0/D7cV91 groups G1
user scott insecure-password elgato groups G1,G2
user xdb insecure-password hello groups G2
Please note that both lists are functionally identical.
3.5. Peers
It is possible to synchronize server entries in stick tables between several haproxy instances over TCP connections in a multi-master fashion. Each instance pushes its local updates and insertions to remote peers. Server IDs are used to identify servers remotely, so it is important that configurations look similar or at least that the same IDs are forced on each server on all participants. Interrupted exchanges are automatically detected and recovered from the last known point. In addition, during a soft restart, the old process connects to the new one using such a TCP connection to push all its entries before the new process tries to connect to other peers. That ensures very fast replication during a reload, it typically takes a fraction of a second even for large tables.
Creates a new peer list with name <peersect>. It is an independent section, which is referenced by one or more stick-tables.
Defines a peer inside a peers section.
If <peername> is set to the local peer name (by default hostname, or forced
using "-L" command line option), haproxy will listen for incoming remote peer
connection on <ip>:<port>. Otherwise, <ip>:<port> defines where to connect to
to join the remote peer, and <peername> is used at the protocol level to
identify and validate the remote peer on the server side.
During a soft restart, local peer <ip>:<port> is used by the old instance to
connect the new one and initiate a complete replication (teaching process).
It is strongly recommended to have the exact same peers declaration on all
peers and to only rely on the "-L" command line argument to change the local
peer name. This makes it easier to maintain coherent configuration files
across all peers.
Any part of the address string may reference any number of environment
variables by preceding their name with a dollar sign ('$') and optionally
enclosing them with braces ('{}'), similarly to what is done in Bourne shell.
Example:
peers mypeers
peer haproxy1 192.168.0.1:1024
peer haproxy2 192.168.0.2:1024
peer haproxy3 10.2.0.1:1024
backend mybackend
mode tcp
balance roundrobin
stick-table type ip size 20k peers mypeers
stick on src
server srv1 192.168.0.30:80
server srv2 192.168.0.31:80
4. Proxies
Proxy configuration can be located in a set of sections : - defaults <name> - frontend <name> - backend <name> - listen <name> A "defaults" section sets default parameters for all other sections following its declaration. Those default parameters are reset by the next "defaults" section. See below for the list of parameters which can be set in a "defaults" section. The name is optional but its use is encouraged for better readability. A "frontend" section describes a set of listening sockets accepting client connections. A "backend" section describes a set of servers to which the proxy will connect to forward incoming connections. A "listen" section defines a complete proxy with its frontend and backend parts combined in one section. It is generally useful for TCP-only traffic. All proxy names must be formed from upper and lower case letters, digits, '-' (dash), '_' (underscore) , '.' (dot) and ':' (colon). ACL names are case-sensitive, which means that "www" and "WWW" are two different proxies. Historically, all proxy names could overlap, it just caused troubles in the logs. Since the introduction of content switching, it is mandatory that two proxies with overlapping capabilities (frontend/backend) have different names. However, it is still permitted that a frontend and a backend share the same name, as this configuration seems to be commonly encountered. Right now, two major proxy modes are supported : "tcp", also known as layer 4, and "http", also known as layer 7. In layer 4 mode, HAProxy simply forwards bidirectional traffic between two sides. In layer 7 mode, HAProxy analyzes the protocol, and can interact with it by allowing, blocking, switching, adding, modifying, or removing arbitrary contents in requests or responses, based on arbitrary criteria.
4.1. Proxy keywords matrix
The following list of keywords is supported. Most of them may only be used in a limited set of section types. Some of them are marked as "deprecated" because they are inherited from an old syntax which may be confusing or functionally limited, and there are new recommended keywords to replace them. Keywords marked with "(*)" can be optionally inverted using the "no" prefix, eg. "no option contstats". This makes sense when the option has been enabled by default and must be disabled for a specific instance. Such options may also be prefixed with "default" in order to restore default settings regardless of what has been specified in a previous "defaults" section.
4.2. Alphabetically sorted keywords reference
This section provides a description of each keyword and its usage.
Declare or complete an access list.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
no | yes | yes | yes |
Example:
acl invalid_src src 0.0.0.0/7 224.0.0.0/3
acl invalid_src src_port 0:1023
acl local_dst hdr(host) -i localhost
See section 7 about ACL usage.
appsession <cookie> len <length> timeout <holdtime>
[request-learn] [prefix] [mode <path-parameters|query-string>]
Define session stickiness on an existing application cookie.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<cookie> this is the name of the cookie used by the application and which
HAProxy will have to learn for each new session.
<length> this is the max number of characters that will be memorized and
checked in each cookie value.
<holdtime> this is the time after which the cookie will be removed from
memory if unused. If no unit is specified, this time is in
milliseconds.
request-learn
If this option is specified, then haproxy will be able to learn
the cookie found in the request in case the server does not
specify any in response. This is typically what happens with
PHPSESSID cookies, or when haproxy's session expires before
the application's session and the correct server is selected.
It is recommended to specify this option to improve reliability.
prefix When this option is specified, haproxy will match on the cookie
prefix (or URL parameter prefix). The appsession value is the
data following this prefix.
Example :
appsession ASPSESSIONID len 64 timeout 3h prefix
This will match the cookie ASPSESSIONIDXXXX=XXXXX,
the appsession value will be XXXX=XXXXX.
mode This option allows to change the URL parser mode.
2 modes are currently supported :
- path-parameters :
The parser looks for the appsession in the path parameters
part (each parameter is separated by a semi-colon), which is
convenient for JSESSIONID for example.
This is the default mode if the option is not set.
- query-string :
In this mode, the parser will look for the appsession in the
query string.
When an application cookie is defined in a backend, HAProxy will check when
the server sets such a cookie, and will store its value in a table, and
associate it with the server's identifier. Up to <length> characters from
the value will be retained. On each connection, haproxy will look for this
cookie both in the "Cookie:" headers, and as a URL parameter (depending on
the mode used). If a known value is found, the client will be directed to the
server associated with this value. Otherwise, the load balancing algorithm is
applied. Cookies are automatically removed from memory when they have been
unused for a duration longer than <holdtime>.
The definition of an application cookie is limited to one per backend.
Note : Consider not using this feature in multi-process mode (nbproc > 1)
unless you know what you do : memory is not shared between the
processes, which can result in random behaviours.
Example :
appsession JSESSIONID len 52 timeout 3h
See also : "cookie", "capture cookie", "balance", "stick", "stick-table", "ignore-persist", "nbproc" and "bind-process".
Give hints to the system about the approximate listen backlog desired size
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<conns> is the number of pending connections. Depending on the operating
system, it may represent the number of already acknowledged
connections, of non-acknowledged ones, or both.
In order to protect against SYN flood attacks, one solution is to increase the system's SYN backlog size. Depending on the system, sometimes it is just tunable via a system parameter, sometimes it is not adjustable at all, and sometimes the system relies on hints given by the application at the time of the listen() syscall. By default, HAProxy passes the frontend's maxconn value to the listen() syscall. On systems which can make use of this value, it can sometimes be useful to be able to specify a different value, hence this backlog parameter. On Linux 2.4, the parameter is ignored by the system. On Linux 2.6, it is used as a hint and the system accepts up to the smallest greater power of two, and never more than some limits (usually 32768).
See also : "maxconn" and the target operating system's tuning guide.
Define the load balancing algorithm to be used in a backend.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<algorithm> is the algorithm used to select a server when doing load
balancing. This only applies when no persistence information
is available, or when a connection is redispatched to another
server. <algorithm> may be one of the following :
roundrobin Each server is used in turns, according to their weights.
This is the smoothest and fairest algorithm when the server's
processing time remains equally distributed. This algorithm
is dynamic, which means that server weights may be adjusted
on the fly for slow starts for instance. It is limited by
design to 4128 active servers per backend. Note that in some
large farms, when a server becomes up after having been down
for a very short time, it may sometimes take a few hundreds
requests for it to be re-integrated into the farm and start
receiving traffic. This is normal, though very rare. It is
indicated here in case you would have the chance to observe
it, so that you don't worry.
static-rr Each server is used in turns, according to their weights.
This algorithm is as similar to roundrobin except that it is
static, which means that changing a server's weight on the
fly will have no effect. On the other hand, it has no design
limitation on the number of servers, and when a server goes
up, it is always immediately reintroduced into the farm, once
the full map is recomputed. It also uses slightly less CPU to
run (around -1%).
leastconn The server with the lowest number of connections receives the
connection. Round-robin is performed within groups of servers
of the same load to ensure that all servers will be used. Use
of this algorithm is recommended where very long sessions are
expected, such as LDAP, SQL, TSE, etc... but is not very well
suited for protocols using short sessions such as HTTP. This
algorithm is dynamic, which means that server weights may be
adjusted on the fly for slow starts for instance.
first The first server with available connection slots receives the
connection. The servers are choosen from the lowest numeric
identifier to the highest (see server parameter "id"), which
defaults to the server's position in the farm. Once a server
reaches its maxconn value, the next server is used. It does
not make sense to use this algorithm without setting maxconn.
The purpose of this algorithm is to always use the smallest
number of servers so that extra servers can be powered off
during non-intensive hours. This algorithm ignores the server
weight, and brings more benefit to long session such as RDP
or IMAP than HTTP, though it can be useful there too. In
order to use this algorithm efficiently, it is recommended
that a cloud controller regularly checks server usage to turn
them off when unused, and regularly checks backend queue to
turn new servers on when the queue inflates. Alternatively,
using "http-check send-state" may inform servers on the load.
source The source IP address is hashed and divided by the total
weight of the running servers to designate which server will
receive the request. This ensures that the same client IP
address will always reach the same server as long as no
server goes down or up. If the hash result changes due to the
number of running servers changing, many clients will be
directed to a different server. This algorithm is generally
used in TCP mode where no cookie may be inserted. It may also
be used on the Internet to provide a best-effort stickiness
to clients which refuse session cookies. This algorithm is
static by default, which means that changing a server's
weight on the fly will have no effect, but this can be
changed using "hash-type".
uri This algorithm hashes either the left part of the URI (before
the question mark) or the whole URI (if the "whole" parameter
is present) and divides the hash value by the total weight of
the running servers. The result designates which server will
receive the request. This ensures that the same URI will
always be directed to the same server as long as no server
goes up or down. This is used with proxy caches and
anti-virus proxies in order to maximize the cache hit rate.
Note that this algorithm may only be used in an HTTP backend.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
This algorithm supports two optional parameters "len" and
"depth", both followed by a positive integer number. These
options may be helpful when it is needed to balance servers
based on the beginning of the URI only. The "len" parameter
indicates that the algorithm should only consider that many
characters at the beginning of the URI to compute the hash.
Note that having "len" set to 1 rarely makes sense since most
URIs start with a leading "/".
The "depth" parameter indicates the maximum directory depth
to be used to compute the hash. One level is counted for each
slash in the request. If both parameters are specified, the
evaluation stops when either is reached.
url_param The URL parameter specified in argument will be looked up in
the query string of each HTTP GET request.
If the modifier "check_post" is used, then an HTTP POST
request entity will be searched for the parameter argument,
when it is not found in a query string after a question mark
('?') in the URL. Optionally, specify a number of octets to
wait for before attempting to search the message body. If the
entity can not be searched, then round robin is used for each
request. For instance, if your clients always send the LB
parameter in the first 128 bytes, then specify that. The
default is 48. The entity data will not be scanned until the
required number of octets have arrived at the gateway, this
is the minimum of: (default/max_wait, Content-Length or first
chunk length). If Content-Length is missing or zero, it does
not need to wait for more data than the client promised to
send. When Content-Length is present and larger than
<max_wait>, then waiting is limited to <max_wait> and it is
assumed that this will be enough data to search for the
presence of the parameter. In the unlikely event that
Transfer-Encoding: chunked is used, only the first chunk is
scanned. Parameter values separated by a chunk boundary, may
be randomly balanced if at all.
If the parameter is found followed by an equal sign ('=') and
a value, then the value is hashed and divided by the total
weight of the running servers. The result designates which
server will receive the request.
This is used to track user identifiers in requests and ensure
that a same user ID will always be sent to the same server as
long as no server goes up or down. If no value is found or if
the parameter is not found, then a round robin algorithm is
applied. Note that this algorithm may only be used in an HTTP
backend. This algorithm is static by default, which means
that changing a server's weight on the fly will have no
effect, but this can be changed using "hash-type".
hdr(<name>) The HTTP header <name> will be looked up in each HTTP
request. Just as with the equivalent ACL 'hdr()' function,
the header name in parenthesis is not case sensitive. If the
header is absent or if it does not contain any value, the
roundrobin algorithm is applied instead.
An optional 'use_domain_only' parameter is available, for
reducing the hash algorithm to the main domain part with some
specific headers such as 'Host'. For instance, in the Host
value "haproxy.1wt.eu", only "1wt" will be considered.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
rdp-cookie
rdp-cookie(<name>)
The RDP cookie <name> (or "mstshash" if omitted) will be
looked up and hashed for each incoming TCP request. Just as
with the equivalent ACL 'req_rdp_cookie()' function, the name
is not case-sensitive. This mechanism is useful as a degraded
persistence mode, as it makes it possible to always send the
same user (or the same session ID) to the same server. If the
cookie is not found, the normal roundrobin algorithm is
used instead.
Note that for this to work, the frontend must ensure that an
RDP cookie is already present in the request buffer. For this
you must use 'tcp-request content accept' rule combined with
a 'req_rdp_cookie_cnt' ACL.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
See also the rdp_cookie pattern fetch function.
<arguments> is an optional list of arguments which may be needed by some
algorithms. Right now, only "url_param" and "uri" support an
optional argument.
balance uri [len <len>] [depth <depth>]
balance url_param <param> [check_post [<max_wait>]]
The load balancing algorithm of a backend is set to roundrobin when no other algorithm, mode nor option have been set. The algorithm may only be set once for each backend.
Examples :
balance roundrobin
balance url_param userid
balance url_param session_id check_post 64
balance hdr(User-Agent)
balance hdr(host)
balance hdr(Host) use_domain_only
Note: the following caveats and limitations on using the "check_post"
extension with "url_param" must be considered :
- all POST requests are eligible for consideration, because there is no way
to determine if the parameters will be found in the body or entity which
may contain binary data. Therefore another method may be required to
restrict consideration of POST requests that have no URL parameters in
the body. (see acl reqideny http_end)
- using a <max_wait> value larger than the request buffer size does not
make sense and is useless. The buffer size is set at build time, and
defaults to 16 kB.
- Content-Encoding is not supported, the parameter search will probably
fail; and load balancing will fall back to Round Robin.
- Expect: 100-continue is not supported, load balancing will fall back to
Round Robin.
- Transfer-Encoding (RFC2616 3.6.1) is only supported in the first chunk.
If the entire parameter value is not present in the first chunk, the
selection of server is undefined (actually, defined by how little
actually appeared in the first chunk).
- This feature does not support generation of a 100, 411 or 501 response.
- In some cases, requesting "check_post" MAY attempt to scan the entire
contents of a message body. Scanning normally terminates when linear
white space or control characters are found, indicating the end of what
might be a URL parameter list. This is probably not a concern with SGML
type message bodies.
Define one or several listening addresses and/or ports in a frontend.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | no |
Arguments :
<address> is optional and can be a host name, an IPv4 address, an IPv6
address, or '*'. It designates the address the frontend will
listen on. If unset, all IPv4 addresses of the system will be
listened on. The same will apply for '*' or the system's
special address "0.0.0.0". The IPv6 equivalent is '::'.
Optionally, an address family prefix may be used before the
address to force the family regardless of the address format,
which can be useful to specify a path to a unix socket with
no slash ('/'). Currently supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'unix@' -> address is a path to a local unix socket
- 'fd@<n>' -> use file descriptor <n> inherited from the
parent. The fd must be bound and may or may not already
be listening.
Any part of the address string may reference any number of
environment variables by preceding their name with a dollar
sign ('$') and optionally enclosing them with braces ('{}'),
similarly to what is done in Bourne shell.
<port_range> is either a unique TCP port, or a port range for which the
proxy will accept connections for the IP address specified
above. The port is mandatory for TCP listeners. Note that in
the case of an IPv6 address, the port is always the number
after the last colon (':'). A range can either be :
- a numerical port (ex: '80')
- a dash-delimited ports range explicitly stating the lower
and upper bounds (ex: '2000-2100') which are included in
the range.
Particular care must be taken against port ranges, because
every <address:port> couple consumes one socket (= a file
descriptor), so it's easy to consume lots of descriptors
with a simple range, and to run out of sockets. Also, each
<address:port> couple must be used only once among all
instances running on a same system. Please note that binding
to ports lower than 1024 generally require particular
privileges to start the program, which are independent of
the 'uid' parameter.
<path> is a UNIX socket path beginning with a slash ('/'). This is
alternative to the TCP listening port. Haproxy will then
receive UNIX connections on the socket located at this place.
The path must begin with a slash and by default is absolute.
It can be relative to the prefix defined by "unix-bind" in
the global section. Note that the total length of the prefix
followed by the socket path cannot exceed some system limits
for UNIX sockets, which commonly are set to 107 characters.
<param*> is a list of parameters common to all sockets declared on the
same line. These numerous parameters depend on OS and build
options and have a complete section dedicated to them. Please
refer to section 5 to for more details.
It is possible to specify a list of address:port combinations delimited by commas. The frontend will then listen on all of these addresses. There is no fixed limit to the number of addresses and ports which can be listened on in a frontend, as well as there is no limit to the number of "bind" statements in a frontend.
Example :
listen http_proxy
bind :80,:443
bind 10.0.0.1:10080,10.0.0.1:10443
bind /var/run/ssl-frontend.sock user root mode 600 accept-proxy
listen http_https_proxy
bind :80
bind :443 ssl crt /etc/haproxy/site.pem
listen http_https_proxy_explicit
bind ipv6@:80
bind ipv4@public_ssl:443 ssl crt /etc/haproxy/site.pem
bind unix@ssl-frontend.sock user root mode 600 accept-proxy
listen external_bind_app1
bind fd@${FD_APP1}
See also : "source", "option forwardfor", "unix-bind" and the PROXY protocol documentation, and section 5 about bind options.
Limit visibility of an instance to a certain set of processes numbers.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
all All process will see this instance. This is the default. It
may be used to override a default value.
odd This instance will be enabled on processes 1,3,5,...31. This
option may be combined with other numbers.
even This instance will be enabled on processes 2,4,6,...32. This
option may be combined with other numbers. Do not use it
with less than 2 processes otherwise some instances might be
missing from all processes.
number The instance will be enabled on this process number or range,
whose values must all be between 1 and 32. You must be
careful not to reference a process number greater than the
configured global.nbproc, otherwise some instances might be
missing from all processes.
This keyword limits binding of certain instances to certain processes. This is useful in order not to have too many processes listening to the same ports. For instance, on a dual-core machine, it might make sense to set 'nbproc 2' in the global section, then distributes the listeners among 'odd' and 'even' instances. At the moment, it is not possible to reference more than 32 processes using this keyword, but this should be more than enough for most setups. Please note that 'all' really means all processes and is not limited to the first 32. If some backends are referenced by frontends bound to other processes, the backend automatically inherits the frontend's processes.
Example :
listen app_ip1
bind 10.0.0.1:80
bind-process odd
listen app_ip2
bind 10.0.0.2:80
bind-process even
listen management
bind 10.0.0.3:80
bind-process 1 2 3 4
listen management
bind 10.0.0.4:80
bind-process 1-4
See also : "nbproc" in global section.
Block a layer 7 request if/unless a condition is matched
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
The HTTP request will be blocked very early in the layer 7 processing if/unless <condition> is matched. A 403 error will be returned if the request is blocked. The condition has to reference ACLs (see section 7). This is typically used to deny access to certain sensitive resources if some conditions are met or not met. There is no fixed limit to the number of "block" statements per instance.
Example:
acl invalid_src src 0.0.0.0/7 224.0.0.0/3
acl invalid_src src_port 0:1023
acl local_dst hdr(host) -i localhost
block if invalid_src || local_dst
See section 7 about ACL usage.
Capture and log a cookie in the request and in the response.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | no |
Arguments :
<name> is the beginning of the name of the cookie to capture. In order
to match the exact name, simply suffix the name with an equal
sign ('='). The full name will appear in the logs, which is
useful with application servers which adjust both the cookie name
and value (eg: ASPSESSIONXXXXX).
<length> is the maximum number of characters to report in the logs, which
include the cookie name, the equal sign and the value, all in the
standard "name=value" form. The string will be truncated on the
right if it exceeds <length>.
Only the first cookie is captured. Both the "cookie" request headers and the "set-cookie" response headers are monitored. This is particularly useful to check for application bugs causing session crossing or stealing between users, because generally the user's cookies can only change on a login page. When the cookie was not presented by the client, the associated log column will report "-". When a request does not cause a cookie to be assigned by the server, a "-" is reported in the response column. The capture is performed in the frontend only because it is necessary that the log format does not change for a given frontend depending on the backends. This may change in the future. Note that there can be only one "capture cookie" statement in a frontend. The maximum capture length is set by the global "tune.http.cookielen" setting and defaults to 63 characters. It is not possible to specify a capture in a "defaults" section.
Example:
capture cookie ASPSESSION len 32
Capture and log the last occurrence of the specified request header.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | no |
Arguments :
<name> is the name of the header to capture. The header names are not
case-sensitive, but it is a common practice to write them as they
appear in the requests, with the first letter of each word in
upper case. The header name will not appear in the logs, only the
value is reported, but the position in the logs is respected.
<length> is the maximum number of characters to extract from the value and
report in the logs. The string will be truncated on the right if
it exceeds <length>.
The complete value of the last occurrence of the header is captured. The
value will be added to the logs between braces ('{}'). If multiple headers
are captured, they will be delimited by a vertical bar ('|') and will appear
in the same order they were declared in the configuration. Non-existent
headers will be logged just as an empty string. Common uses for request
header captures include the "Host" field in virtual hosting environments, the
"Content-length" when uploads are supported, "User-agent" to quickly
differentiate between real users and robots, and "X-Forwarded-For" in proxied
environments to find where the request came from.
Note that when capturing headers such as "User-agent", some spaces may be
logged, making the log analysis more difficult. Thus be careful about what
you log if you know your log parser is not smart enough to rely on the
braces.
There is no limit to the number of captured request headers nor to their
length, though it is wise to keep them low to limit memory usage per session.
In order to keep log format consistent for a same frontend, header captures
can only be declared in a frontend. It is not possible to specify a capture
in a "defaults" section.
Example:
capture request header Host len 15
capture request header X-Forwarded-For len 15
capture request header Referrer len 15
Capture and log the last occurrence of the specified response header.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | no |
Arguments :
<name> is the name of the header to capture. The header names are not
case-sensitive, but it is a common practice to write them as they
appear in the response, with the first letter of each word in
upper case. The header name will not appear in the logs, only the
value is reported, but the position in the logs is respected.
<length> is the maximum number of characters to extract from the value and
report in the logs. The string will be truncated on the right if
it exceeds <length>.
The complete value of the last occurrence of the header is captured. The
result will be added to the logs between braces ('{}') after the captured
request headers. If multiple headers are captured, they will be delimited by
a vertical bar ('|') and will appear in the same order they were declared in
the configuration. Non-existent headers will be logged just as an empty
string. Common uses for response header captures include the "Content-length"
header which indicates how many bytes are expected to be returned, the
"Location" header to track redirections.
There is no limit to the number of captured response headers nor to their
length, though it is wise to keep them low to limit memory usage per session.
In order to keep log format consistent for a same frontend, header captures
can only be declared in a frontend. It is not possible to specify a capture
in a "defaults" section.
Example:
capture response header Content-length len 9
capture response header Location len 15
Set the maximum inactivity time on the client side.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<timeout> is the timeout value is specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The inactivity timeout applies when the client is expected to acknowledge or send data. In HTTP mode, this timeout is particularly important to consider during the first phase, when the client sends the request, and during the response while it is reading data sent by the server. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly recommended that the client timeout remains equal to the server timeout in order to avoid complex situations to debug. It is a good practice to cover one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds). This parameter is specific to frontends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of expired sessions in the system if the system's timeouts are not configured either. This parameter is provided for compatibility but is currently deprecated. Please use "timeout client" instead.
Enable HTTP compression.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
algo is followed by the list of supported compression algorithms. type is followed by the list of MIME types that will be compressed. offload makes haproxy work as a compression offloader only (see notes).
The currently supported algorithms are :
identity this is mostly for debugging, and it was useful for developing
the compression feature. Identity does not apply any change on
data.
gzip applies gzip compression. This setting is only available when
support for zlib was built in.
deflate same as gzip, but with deflate algorithm and zlib format.
Note that this algorithm has ambiguous support on many browsers
and no support at all from recent ones. It is strongly
recommended not to use it for anything else than experimentation.
This setting is only available when support for zlib was built
in.
Compression will be activated depending on the Accept-Encoding request
header. With identity, it does not take care of that header.
If backend servers support HTTP compression, these directives
will be no-op: haproxy will see the compressed response and will not
compress again. If backend servers do not support HTTP compression and
there is Accept-Encoding header in request, haproxy will compress the
matching response.
The "offload" setting makes haproxy remove the Accept-Encoding header to
prevent backend servers from compressing responses. It is strongly
recommended not to do this because this means that all the compression work
will be done on the single point where haproxy is located. However in some
deployment scenarios, haproxy may be installed in front of a buggy gateway
with broken HTTP compression implementation which can't be turned off.
In that case haproxy can be used to prevent that gateway from emitting
invalid payloads. In this case, simply removing the header in the
configuration does not work because it applies before the header is parsed,
so that prevents haproxy from compressing. The "offload" setting should
then be used for such scenarios.
Compression is disabled when:
* the request does not advertise a supported compression algorithm in the
"Accept-Encoding" header
* the response message is not HTTP/1.1
* HTTP status code is not 200
* response contain neither a "Content-Length" header nor a
"Transfer-Encoding" whose last value is "chunked"
* response contains a "Content-Type" header whose first value starts with
"multipart"
* the response contains the "no-transform" value in the "Cache-control"
header
* User-Agent matches "Mozilla/4" unless it is MSIE 6 with XP SP2, or MSIE 7
and later
* The response contains a "Content-Encoding" header, indicating that the
response is already compressed (see compression offload)
Note: The compression does not rewrite Etag headers, and does not emit the
Warning header.
Examples :
compression algo gzip
compression type text/html text/plain
Set the maximum time to wait for a connection attempt to a server to succeed.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<timeout> is the timeout value is specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
If the server is located on the same LAN as haproxy, the connection should be immediate (less than a few milliseconds). Anyway, it is a good practice to cover one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds). By default, the connect timeout also presets the queue timeout to the same value if this one has not been specified. Historically, the contimeout was also used to set the tarpit timeout in a listen section, which is not possible in a pure frontend. This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of failed sessions in the system if the system's timeouts are not configured either. This parameter is provided for backwards compatibility but is currently deprecated. Please use "timeout connect", "timeout queue" or "timeout tarpit" instead.
cookie <name> [ rewrite | insert | prefix ] [ indirect ] [ nocache ]
[ postonly ] [ preserve ] [ httponly ] [ secure ]
[ domain <domain> ]* [ maxidle <idle> ] [ maxlife <life> ]
Enable cookie-based persistence in a backend.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<name> is the name of the cookie which will be monitored, modified or
inserted in order to bring persistence. This cookie is sent to
the client via a "Set-Cookie" header in the response, and is
brought back by the client in a "Cookie" header in all requests.
Special care should be taken to choose a name which does not
conflict with any likely application cookie. Also, if the same
backends are subject to be used by the same clients (eg:
HTTP/HTTPS), care should be taken to use different cookie names
between all backends if persistence between them is not desired.
rewrite This keyword indicates that the cookie will be provided by the
server and that haproxy will have to modify its value to set the
server's identifier in it. This mode is handy when the management
of complex combinations of "Set-cookie" and "Cache-control"
headers is left to the application. The application can then
decide whether or not it is appropriate to emit a persistence
cookie. Since all responses should be monitored, this mode only
works in HTTP close mode. Unless the application behaviour is
very complex and/or broken, it is advised not to start with this
mode for new deployments. This keyword is incompatible with
"insert" and "prefix".
insert This keyword indicates that the persistence cookie will have to
be inserted by haproxy in server responses if the client did not
already have a cookie that would have permitted it to access this
server. When used without the "preserve" option, if the server
emits a cookie with the same name, it will be remove before
processing. For this reason, this mode can be used to upgrade
existing configurations running in the "rewrite" mode. The cookie
will only be a session cookie and will not be stored on the
client's disk. By default, unless the "indirect" option is added,
the server will see the cookies emitted by the client. Due to
caching effects, it is generally wise to add the "nocache" or
"postonly" keywords (see below). The "insert" keyword is not
compatible with "rewrite" and "prefix".
prefix This keyword indicates that instead of relying on a dedicated
cookie for the persistence, an existing one will be completed.
This may be needed in some specific environments where the client
does not support more than one single cookie and the application
already needs it. In this case, whenever the server sets a cookie
named <name>, it will be prefixed with the server's identifier
and a delimiter. The prefix will be removed from all client
requests so that the server still finds the cookie it emitted.
Since all requests and responses are subject to being modified,
this mode requires the HTTP close mode. The "prefix" keyword is
not compatible with "rewrite" and "insert". Note: it is highly
recommended not to use "indirect" with "prefix", otherwise server
cookie updates would not be sent to clients.
indirect When this option is specified, no cookie will be emitted to a
client which already has a valid one for the server which has
processed the request. If the server sets such a cookie itself,
it will be removed, unless the "preserve" option is also set. In
"insert" mode, this will additionally remove cookies from the
requests transmitted to the server, making the persistence
mechanism totally transparent from an application point of view.
Note: it is highly recommended not to use "indirect" with
"prefix", otherwise server cookie updates would not be sent to
clients.
nocache This option is recommended in conjunction with the insert mode
when there is a cache between the client and HAProxy, as it
ensures that a cacheable response will be tagged non-cacheable if
a cookie needs to be inserted. This is important because if all
persistence cookies are added on a cacheable home page for
instance, then all customers will then fetch the page from an
outer cache and will all share the same persistence cookie,
leading to one server receiving much more traffic than others.
See also the "insert" and "postonly" options.
postonly This option ensures that cookie insertion will only be performed
on responses to POST requests. It is an alternative to the
"nocache" option, because POST responses are not cacheable, so
this ensures that the persistence cookie will never get cached.
Since most sites do not need any sort of persistence before the
first POST which generally is a login request, this is a very
efficient method to optimize caching without risking to find a
persistence cookie in the cache.
See also the "insert" and "nocache" options.
preserve This option may only be used with "insert" and/or "indirect". It
allows the server to emit the persistence cookie itself. In this
case, if a cookie is found in the response, haproxy will leave it
untouched. This is useful in order to end persistence after a
logout request for instance. For this, the server just has to
emit a cookie with an invalid value (eg: empty) or with a date in
the past. By combining this mechanism with the "disable-on-404"
check option, it is possible to perform a completely graceful
shutdown because users will definitely leave the server after
they logout.
httponly This option tells haproxy to add an "HttpOnly" cookie attribute
when a cookie is inserted. This attribute is used so that a
user agent doesn't share the cookie with non-HTTP components.
Please check RFC6265 for more information on this attribute.
secure This option tells haproxy to add a "Secure" cookie attribute when
a cookie is inserted. This attribute is used so that a user agent
never emits this cookie over non-secure channels, which means
that a cookie learned with this flag will be presented only over
SSL/TLS connections. Please check RFC6265 for more information on
this attribute.
domain This option allows to specify the domain at which a cookie is
inserted. It requires exactly one parameter: a valid domain
name. If the domain begins with a dot, the browser is allowed to
use it for any host ending with that name. It is also possible to
specify several domain names by invoking this option multiple
times. Some browsers might have small limits on the number of
domains, so be careful when doing that. For the record, sending
10 domains to MSIE 6 or Firefox 2 works as expected.
maxidle This option allows inserted cookies to be ignored after some idle
time. It only works with insert-mode cookies. When a cookie is
sent to the client, the date this cookie was emitted is sent too.
Upon further presentations of this cookie, if the date is older
than the delay indicated by the parameter (in seconds), it will
be ignored. Otherwise, it will be refreshed if needed when the
response is sent to the client. This is particularly useful to
prevent users who never close their browsers from remaining for
too long on the same server (eg: after a farm size change). When
this option is set and a cookie has no date, it is always
accepted, but gets refreshed in the response. This maintains the
ability for admins to access their sites. Cookies that have a
date in the future further than 24 hours are ignored. Doing so
lets admins fix timezone issues without risking kicking users off
the site.
maxlife This option allows inserted cookies to be ignored after some life
time, whether they're in use or not. It only works with insert
mode cookies. When a cookie is first sent to the client, the date
this cookie was emitted is sent too. Upon further presentations
of this cookie, if the date is older than the delay indicated by
the parameter (in seconds), it will be ignored. If the cookie in
the request has no date, it is accepted and a date will be set.
Cookies that have a date in the future further than 24 hours are
ignored. Doing so lets admins fix timezone issues without risking
kicking users off the site. Contrary to maxidle, this value is
not refreshed, only the first visit date counts. Both maxidle and
maxlife may be used at the time. This is particularly useful to
prevent users who never close their browsers from remaining for
too long on the same server (eg: after a farm size change). This
is stronger than the maxidle method in that it forces a
redispatch after some absolute delay.
There can be only one persistence cookie per HTTP backend, and it can be declared in a defaults section. The value of the cookie will be the value indicated after the "cookie" keyword in a "server" statement. If no cookie is declared for a given server, the cookie is not set.
Examples :
cookie JSESSIONID prefix
cookie SRV insert indirect nocache
cookie SRV insert postonly indirect
cookie SRV insert indirect nocache maxidle 30m maxlife 8h
Change default options for a server in a backend
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments:
<param*> is a list of parameters for this server. The "default-server" keyword accepts an important number of options and has a complete section dedicated to it. Please refer to section 5 for more details.
Example :
default-server inter 1000 weight 13
Specify the backend to use when no "use_backend" rule has been matched.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<backend> is the name of the backend to use.
When doing content-switching between frontend and backends using the "use_backend" keyword, it is often useful to indicate which backend will be used when no rule has matched. It generally is the dynamic backend which will catch all undetermined requests.
Example :
use_backend dynamic if url_dyn
use_backend static if url_css url_img extension_img
default_backend dynamic
See also : "use_backend", "reqsetbe", "reqisetbe"
Disable a proxy, frontend or backend.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
The "disabled" keyword is used to disable an instance, mainly in order to liberate a listening port or to temporarily disable a service. The instance will still be created and its configuration will be checked, but it will be created in the "stopped" state and will appear as such in the statistics. It will not receive any traffic nor will it send any health-checks or logs. It is possible to disable many instances at once by adding the "disabled" keyword in a "defaults" section.
See also : "enabled"
Set a default server address
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<address> is the IPv4 address of the default server. Alternatively, a
resolvable hostname is supported, but this name will be resolved
during start-up.
<ports> is a mandatory port specification. All connections will be sent
to this port, and it is not permitted to use port offsets as is
possible with normal servers.
The "dispatch" keyword designates a default server for use when no other server can take the connection. In the past it was used to forward non persistent connections to an auxiliary load balancer. Due to its simple syntax, it has also been used for simple TCP relays. It is recommended not to use it for more clarity, and to use the "server" directive instead.
See also : "server"
Enable a proxy, frontend or backend.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
The "enabled" keyword is used to explicitly enable an instance, when the defaults has been set to "disabled". This is very rarely used.
See also : "disabled"
Return a file contents instead of errors generated by HAProxy
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 403, 408, 500, 502, 503, and 504.
<file> designates a file containing the full HTTP response. It is
recommended to follow the common practice of appending ".http" to
the filename so that people do not confuse the response with HTML
error pages, and to use absolute paths, since files are read
before any chroot is performed.
It is important to understand that this keyword is not meant to rewrite errors returned by the server, but errors detected and returned by HAProxy. This is why the list of supported errors is limited to a small set. Code 200 is emitted in response to requests matching a "monitor-uri" rule. The files are returned verbatim on the TCP socket. This allows any trick such as redirections to another URL or site, as well as tricks to clean cookies, force enable or disable caching, etc... The package provides default error files returning the same contents as default errors. The files should not exceed the configured buffer size (BUFSIZE), which generally is 8 or 16 kB, otherwise they will be truncated. It is also wise not to put any reference to local contents (eg: images) in order to avoid loops between the client and HAProxy when all servers are down, causing an error to be returned instead of an image. For better HTTP compliance, it is recommended that all header lines end with CR-LF and not LF alone. The files are read at the same time as the configuration and kept in memory. For this reason, the errors continue to be returned even when the process is chrooted, and no file change is considered while the process is running. A simple method for developing those files consists in associating them to the 403 status code and interrogating a blocked URL.
Example :
errorfile 400 /etc/haproxy/errorfiles/400badreq.http
errorfile 403 /etc/haproxy/errorfiles/403forbid.http
errorfile 503 /etc/haproxy/errorfiles/503sorry.http
Return an HTTP redirection to a URL instead of errors generated by HAProxy
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 403, 408, 500, 502, 503, and 504.
<url> it is the exact contents of the "Location" header. It may contain
either a relative URI to an error page hosted on the same site,
or an absolute URI designating an error page on another site.
Special care should be given to relative URIs to avoid redirect
loops if the URI itself may generate the same error (eg: 500).
It is important to understand that this keyword is not meant to rewrite errors returned by the server, but errors detected and returned by HAProxy. This is why the list of supported errors is limited to a small set. Code 200 is emitted in response to requests matching a "monitor-uri" rule. Note that both keyword return the HTTP 302 status code, which tells the client to fetch the designated URL using the same HTTP method. This can be quite problematic in case of non-GET methods such as POST, because the URL sent to the client might not be allowed for something other than GET. To workaround this problem, please use "errorloc303" which send the HTTP 303 status code, indicating to the client that the URL must be fetched with a GET request.
See also : "errorfile", "errorloc303"
Return an HTTP redirection to a URL instead of errors generated by HAProxy
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 400, 403, 408, 500, 502, 503, and 504.
<url> it is the exact contents of the "Location" header. It may contain
either a relative URI to an error page hosted on the same site,
or an absolute URI designating an error page on another site.
Special care should be given to relative URIs to avoid redirect
loops if the URI itself may generate the same error (eg: 500).
It is important to understand that this keyword is not meant to rewrite errors returned by the server, but errors detected and returned by HAProxy. This is why the list of supported errors is limited to a small set. Code 200 is emitted in response to requests matching a "monitor-uri" rule. Note that both keyword return the HTTP 303 status code, which tells the client to fetch the designated URL using the same HTTP GET method. This solves the usual problems associated with "errorloc" and the 302 code. It is possible that some very old browsers designed before HTTP/1.1 do not support it, but no such problem has been reported till now.
Declare a condition to force persistence on down servers
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
By default, requests are not dispatched to down servers. It is possible to force this using "option persist", but it is unconditional and redispatches to a valid server if "option redispatch" is set. That leaves with very little possibilities to force some requests to reach a server which is artificially marked down for maintenance operations. The "force-persist" statement allows one to declare various ACL-based conditions which, when met, will cause a request to ignore the down status of a server and still try to connect to it. That makes it possible to start a server, still replying an error to the health checks, and run a specially configured browser to test the service. Among the handy methods, one could use a specific source IP address, or a specific cookie. The cookie also has the advantage that it can easily be added/removed on the browser from a test page. Once the service is validated, it is then possible to open the service to the world by returning a valid response to health checks. The forced persistence is enabled when an "if" condition is met, or unless an "unless" condition is met. The final redispatch is always disabled when this is used.
Specify at what backend load the servers will reach their maxconn
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<conns> is the number of connections on the backend which will make the
servers use the maximal number of connections.
When a server has a "maxconn" parameter specified, it means that its number of concurrent connections will never go higher. Additionally, if it has a "minconn" parameter, it indicates a dynamic limit following the backend's load. The server will then always accept at least <minconn> connections, never more than <maxconn>, and the limit will be on the ramp between both values when the backend has less than <conns> concurrent connections. This makes it possible to limit the load on the servers during normal loads, but push it further for important loads without overloading the servers during exceptional loads. Since it's hard to get this value right, haproxy automatically sets it to 10% of the sum of the maxconns of all frontends that may branch to this backend. That way it's safe to leave it unset.
Example :
# The servers will accept between 100 and 1000 concurrent connections each
# and the maximum of 1000 will be reached when the backend reaches 10000
# connections.
backend dynamic
fullconn 10000
server srv1 dyn1:80 minconn 100 maxconn 1000
server srv2 dyn2:80 minconn 100 maxconn 1000
Maintain a proxy operational for some time after a soft stop
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<time> is the time (by default in milliseconds) for which the instance
will remain operational with the frontend sockets still listening
when a soft-stop is received via the SIGUSR1 signal.
This may be used to ensure that the services disappear in a certain order. This was designed so that frontends which are dedicated to monitoring by an external equipment fail immediately while other ones remain up for the time needed by the equipment to detect the failure. Note that currently, there is very little benefit in using this parameter, and it may in fact complicate the soft-reconfiguration process more than simplify it.
Specify a method to use for mapping hashes to servers
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
map-based the hash table is a static array containing all alive servers.
The hashes will be very smooth, will consider weights, but will
be static in that weight changes while a server is up will be
ignored. This means that there will be no slow start. Also,
since a server is selected by its position in the array, most
mappings are changed when the server count changes. This means
that when a server goes up or down, or when a server is added
to a farm, most connections will be redistributed to different
servers. This can be inconvenient with caches for instance.
avalanche this mechanism uses the default map-based hashing described
above but applies a full avalanche hash before performing the
mapping. The result is a slightly less smooth hash for most
situations, but the hash becomes better than pure map-based
hashes when the number of servers is a multiple of the size of
the input set. When using URI hash with a number of servers
multiple of 64, it's desirable to change the hash type to
this value.
consistent the hash table is a tree filled with many occurrences of each
server. The hash key is looked up in the tree and the closest
server is chosen. This hash is dynamic, it supports changing
weights while the servers are up, so it is compatible with the
slow start feature. It has the advantage that when a server
goes up or down, only its associations are moved. When a server
is added to the farm, only a few part of the mappings are
redistributed, making it an ideal algorithm for caches.
However, due to its principle, the algorithm will never be very
smooth and it may sometimes be necessary to adjust a server's
weight or its ID to get a more balanced distribution. In order
to get the same distribution on multiple load balancers, it is
important that all servers have the same IDs.
The default hash type is "map-based" and is recommended for most usages.
Enable a maintenance mode upon HTTP/404 response to health-checks
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
When this option is set, a server which returns an HTTP code 404 will be excluded from further load-balancing, but will still receive persistent connections. This provides a very convenient method for Web administrators to perform a graceful shutdown of their servers. It is also important to note that a server which is detected as failed while it was in this mode will not generate an alert, just a notice. If the server responds 2xx or 3xx again, it will immediately be reinserted into the farm. The status on the stats page reports "NOLB" for a server in this mode. It is important to note that this option only works in conjunction with the "httpchk" option. If this option is used with "http-check expect", then it has precedence over it so that 404 responses will still be considered as soft-stop.
See also : "option httpchk", "http-check expect"
Make HTTP health checks consider response contents or specific status codes
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<match> is a keyword indicating how to look for a specific pattern in the
response. The keyword may be one of "status", "rstatus",
"string", or "rstring". The keyword may be preceded by an
exclamation mark ("!") to negate the match. Spaces are allowed
between the exclamation mark and the keyword. See below for more
details on the supported keywords.
<pattern> is the pattern to look for. It may be a string or a regular
expression. If the pattern contains spaces, they must be escaped
with the usual backslash ('\').
By default, "option httpchk" considers that response statuses 2xx and 3xx are valid, and that others are invalid. When "http-check expect" is used, it defines what is considered valid or invalid. Only one "http-check" statement is supported in a backend. If a server fails to respond or times out, the check obviously fails. The available matches are : status <string> : test the exact string match for the HTTP status code. A health check response will be considered valid if the response's status code is exactly this string. If the "status" keyword is prefixed with "!", then the response will be considered invalid if the status code matches. rstatus <regex> : test a regular expression for the HTTP status code. A health check response will be considered valid if the response's status code matches the expression. If the "rstatus" keyword is prefixed with "!", then the response will be considered invalid if the status code matches. This is mostly used to check for multiple codes. string <string> : test the exact string match in the HTTP response body. A health check response will be considered valid if the response's body contains this exact string. If the "string" keyword is prefixed with "!", then the response will be considered invalid if the body contains this string. This can be used to look for a mandatory word at the end of a dynamic page, or to detect a failure when a specific error appears on the check page (eg: a stack trace). rstring <regex> : test a regular expression on the HTTP response body. A health check response will be considered valid if the response's body matches this expression. If the "rstring" keyword is prefixed with "!", then the response will be considered invalid if the body matches the expression. This can be used to look for a mandatory word at the end of a dynamic page, or to detect a failure when a specific error appears on the check page (eg: a stack trace). It is important to note that the responses will be limited to a certain size defined by the global "tune.chksize" option, which defaults to 16384 bytes. Thus, too large responses may not contain the mandatory pattern when using "string" or "rstring". If a large response is absolutely required, it is possible to change the default max size by setting the global variable. However, it is worth keeping in mind that parsing very large responses can waste some CPU cycles, especially when regular expressions are used, and that it is always better to focus the checks on smaller resources. Last, if "http-check expect" is combined with "http-check disable-on-404", then this last one has precedence when the server responds with 404.
Examples :
# only accept status 200 as valid
http-check expect status 200
# consider SQL errors as errors
http-check expect ! string SQL\ Error
# consider status 5xx only as errors
http-check expect ! rstatus ^5
# check that we have a correct hexadecimal tag before /html
http-check expect rstring <!--tag:[0-9a-f]*</html>
See also : "option httpchk", "http-check disable-on-404"
Enable emission of a state header with HTTP health checks
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
When this option is set, haproxy will systematically send a special header
"X-Haproxy-Server-State" with a list of parameters indicating to each server
how they are seen by haproxy. This can be used for instance when a server is
manipulated without access to haproxy and the operator needs to know whether
haproxy still sees it up or not, or if the server is the last one in a farm.
The header is composed of fields delimited by semi-colons, the first of which
is a word ("UP", "DOWN", "NOLB"), possibly followed by a number of valid
checks on the total number before transition, just as appears in the stats
interface. Next headers are in the form "<variable>=<value>", indicating in
no specific order some values available in the stats interface :
- a variable "name", containing the name of the backend followed by a slash
("/") then the name of the server. This can be used when a server is
checked in multiple backends.
- a variable "node" containing the name of the haproxy node, as set in the
global "node" variable, otherwise the system's hostname if unspecified.
- a variable "weight" indicating the weight of the server, a slash ("/")
and the total weight of the farm (just counting usable servers). This
helps to know if other servers are available to handle the load when this
one fails.
- a variable "scur" indicating the current number of concurrent connections
on the server, followed by a slash ("/") then the total number of
connections on all servers of the same backend.
- a variable "qcur" indicating the current number of requests in the
server's queue.
Example of a header received by the application server :
>>> X-Haproxy-Server-State: UP 2/3; name=bck/srv2; node=lb1; weight=1/2; \
scur=13/22; qcur=0See also : "option httpchk", "http-check disable-on-404"
http-request { allow | deny | tarpit | auth [realm <realm>] | redirect <rule> |
add-header <name> <fmt> | set-header <name> <fmt> }
[ { if | unless } <condition> ]
Access control for Layer 7 requests
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
The http-request statement defines a set of rules which apply to layer 7
processing. The rules are evaluated in their declaration order when they are
met in a frontend, listen or backend section. Any rule may optionally be
followed by an ACL-based condition, in which case it will only be evaluated
if the condition is true.
The first keyword is the rule's action. Currently supported actions include :
- "allow" : this stops the evaluation of the rules and lets the request
pass the check. No further "http-request" rules are evaluated.
- "deny" : this stops the evaluation of the rules and immediately rejects
the request and emits an HTTP 403 error. No further "http-request" rules
are evaluated.
- "tarpit" : this stops the evaluation of the rules and immediately blocks
the request without responding for a delay specified by "timeout tarpit"
or "timeout connect" if the former is not set. After that delay, if the
client is still connected, an HTTP error 500 is returned so that the
client does not suspect it has been tarpitted. Logs will report the flags
"PT". The goal of the tarpit rule is to slow down robots during an attack
when they're limited on the number of concurrent requests. It can be very
efficient against very dumb robots, and will significantly reduce the
load on firewalls compared to a "deny" rule. But when facing "correctly"
developped robots, it can make things worse by forcing haproxy and the
front firewall to support insane number of concurrent connections.
- "auth" : this stops the evaluation of the rules and immediately responds
with an HTTP 401 or 407 error code to invite the user to present a valid
user name and password. No further "http-request" rules are evaluated. An
optional "realm" parameter is supported, it sets the authentication realm
that is returned with the response (typically the application's name).
- "redirect" : this performs an HTTP redirection based on a redirect rule.
This is exactly the same as the "redirect" statement except that it
inserts a redirect rule which can be processed in the middle of other
"http-request" rules. See the "redirect" keyword for the rule's syntax.
- "add-header" appends an HTTP header field whose name is specified in
<name> and whose value is defined by <fmt> which follows the log-format
rules (see Custom Log Format in section 8.2.4). This is particularly
useful to pass connection-specific information to the server (eg: the
client's SSL certificate), or to combine several headers into one. This
rule is not final, so it is possible to add other similar rules. Note
that header addition is performed immediately, so one rule might reuse
the resulting header from a previous rule.
- "set-header" does the same as "add-header" except that the header name
is first removed if it existed. This is useful when passing security
information to the server, where the header must not be manipulated by
external users.
There is no limit to the number of http-request statements per instance.
It is important to know that http-request rules are processed very early in
the HTTP processing, just after "block" rules and before "reqdel" or "reqrep"
rules. That way, headers added by "add-header"/"set-header" are visible by
almost all further ACL rules.
Example:
acl nagios src 192.168.129.3
acl local_net src 192.168.0.0/16
acl auth_ok http_auth(L1)
http-request allow if nagios
http-request allow if local_net auth_ok
http-request auth realm Gimme if local_net auth_ok
http-request deny
Example:
acl auth_ok http_auth_group(L1) G1
http-request auth unless auth_ok
Example:
http-request set-header X-Haproxy-Current-Date %T
http-request set-header X-SSL %[ssl_fc]
http-request set-header X-SSL-Session_ID %[ssl_fc_session_id]
http-request set-header X-SSL-Client-Verify %[ssl_c_verify]
http-request set-header X-SSL-Client-DN %{+Q}[ssl_c_s_dn]
http-request set-header X-SSL-Client-CN %{+Q}[ssl_c_s_dn(cn)]
http-request set-header X-SSL-Issuer %{+Q}[ssl_c_i_dn]
http-request set-header X-SSL-Client-NotBefore %{+Q}[ssl_c_notbefore]
http-request set-header X-SSL-Client-NotAfter %{+Q}[ssl_c_notafter]
Add the server name to a request. Use the header string given by <header>
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<header> The header string to use to send the server name
The "http-send-name-header" statement causes the name of the target server to be added to the headers of an HTTP request. The name is added with the header string proved.
See also : "server"
Set a persistent ID to a proxy.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments : none
Set a persistent ID for the proxy. This ID must be unique and positive. An unused ID will automatically be assigned if unset. The first assigned value will be 1. This ID is currently only returned in statistics.
Declare a condition to ignore persistence
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
By default, when cookie persistence is enabled, every requests containing the cookie are unconditionally persistent (assuming the target server is up and running). The "ignore-persist" statement allows one to declare various ACL-based conditions which, when met, will cause a request to ignore persistence. This is sometimes useful to load balance requests for static files, which oftenly don't require persistence. This can also be used to fully disable persistence for a specific User-Agent (for example, some web crawler bots). Combined with "appsession", it can also help reduce HAProxy memory usage, as the appsession table won't grow if persistence is ignored. The persistence is ignored when an "if" condition is met, or unless an "unless" condition is met.
Enable per-instance logging of events and traffic.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Prefix :
no should be used when the logger list must be flushed. For example,
if you don't want to inherit from the default logger list. This
prefix does not allow arguments.
Arguments :
global should be used when the instance's logging parameters are the
same as the global ones. This is the most common usage. "global"
replaces <address>, <facility> and <level> with those of the log
entries found in the "global" section. Only one "log global"
statement may be used per instance, and this form takes no other
parameter.
<address> indicates where to send the logs. It takes the same format as
for the "global" section's logs, and can be one of :
- An IPv4 address optionally followed by a colon (':') and a UDP
port. If no port is specified, 514 is used by default (the
standard syslog port).
- An IPv6 address followed by a colon (':') and optionally a UDP
port. If no port is specified, 514 is used by default (the
standard syslog port).
- A filesystem path to a UNIX domain socket, keeping in mind
considerations for chroot (be sure the path is accessible
inside the chroot) and uid/gid (be sure the path is
appropriately writeable).
Any part of the address string may reference any number of
environment variables by preceding their name with a dollar
sign ('$') and optionally enclosing them with braces ('{}'),
similarly to what is done in Bourne shell.
<facility> must be one of the 24 standard syslog facilities :
kern user mail daemon auth syslog lpr news
uucp cron auth2 ftp ntp audit alert cron2
local0 local1 local2 local3 local4 local5 local6 local7
<level> is optional and can be specified to filter outgoing messages. By
default, all messages are sent. If a level is specified, only
messages with a severity at least as important as this level
will be sent. An optional minimum level can be specified. If it
is set, logs emitted with a more severe level than this one will
be capped to this level. This is used to avoid sending "emerg"
messages on all terminals on some default syslog configurations.
Eight levels are known :
emerg alert crit err warning notice info debug
It is important to keep in mind that it is the frontend which decides what to
log from a connection, and that in case of content switching, the log entries
from the backend will be ignored. Connections are logged at level "info".
However, backend log declaration define how and where servers status changes
will be logged. Level "notice" will be used to indicate a server going up,
"warning" will be used for termination signals and definitive service
termination, and "alert" will be used for when a server goes down.
Note : According to RFC3164, messages are truncated to 1024 bytes before
being emitted.
Example :
log global
log 127.0.0.1:514 local0 notice # only send important events
log 127.0.0.1:514 local0 notice notice # same but limit output level
log ${LOCAL_SYSLOG}:514 local0 notice # send to local server
See also : Custom Log Format (8.2.4)
Fix the maximum number of concurrent connections on a frontend
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<conns> is the maximum number of concurrent connections the frontend will
accept to serve. Excess connections will be queued by the system
in the socket's listen queue and will be served once a connection
closes.
If the system supports it, it can be useful on big sites to raise this limit very high so that haproxy manages connection queues, instead of leaving the clients with unanswered connection attempts. This value should not exceed the global maxconn. Also, keep in mind that a connection contains two buffers of 8kB each, as well as some other data resulting in about 17 kB of RAM being consumed per established connection. That means that a medium system equipped with 1GB of RAM can withstand around 40000-50000 concurrent connections if properly tuned. Also, when <conns> is set to large values, it is possible that the servers are not sized to accept such loads, and for this reason it is generally wise to assign them some reasonable connection limits. By default, this value is set to 2000.
Set the running mode or protocol of the instance
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
tcp The instance will work in pure TCP mode. A full-duplex connection
will be established between clients and servers, and no layer 7
examination will be performed. This is the default mode. It
should be used for SSL, SSH, SMTP, ...
http The instance will work in HTTP mode. The client request will be
analyzed in depth before connecting to any server. Any request
which is not RFC-compliant will be rejected. Layer 7 filtering,
processing and switching will be possible. This is the mode which
brings HAProxy most of its value.
health The instance will work in "health" mode. It will just reply "OK"
to incoming connections and close the connection. Alternatively,
If the "httpchk" option is set, "HTTP/1.0 200 OK" will be sent
instead. Nothing will be logged in either case. This mode is used
to reply to external components health checks. This mode is
deprecated and should not be used anymore as it is possible to do
the same and even better by combining TCP or HTTP modes with the
"monitor" keyword.
When doing content switching, it is mandatory that the frontend and the backend are in the same mode (generally HTTP), otherwise the configuration will be refused.
Example :
defaults http_instances
mode http
See also : "monitor", "monitor-net"
Add a condition to report a failure to a monitor HTTP request.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | no |
Arguments :
if <cond> the monitor request will fail if the condition is satisfied,
and will succeed otherwise. The condition should describe a
combined test which must induce a failure if all conditions
are met, for instance a low number of servers both in a
backend and its backup.
unless <cond> the monitor request will succeed only if the condition is
satisfied, and will fail otherwise. Such a condition may be
based on a test on the presence of a minimum number of active
servers in a list of backends.
This statement adds a condition which can force the response to a monitor request to report a failure. By default, when an external component queries the URI dedicated to monitoring, a 200 response is returned. When one of the conditions above is met, haproxy will return 503 instead of 200. This is very useful to report a site failure to an external component which may base routing advertisements between multiple sites on the availability reported by haproxy. In this case, one would rely on an ACL involving the "nbsrv" criterion. Note that "monitor fail" only works in HTTP mode. Both status messages may be tweaked using "errorfile" or "errorloc" if needed.
Example:
frontend www
mode http
acl site_dead nbsrv(dynamic) lt 2
acl site_dead nbsrv(static) lt 2
monitor-uri /site_alive
monitor fail if site_dead
Declare a source network which is limited to monitor requests
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<source> is the source IPv4 address or network which will only be able to
get monitor responses to any request. It can be either an IPv4
address, a host name, or an address followed by a slash ('/')
followed by a mask.
In TCP mode, any connection coming from a source matching <source> will cause the connection to be immediately closed without any log. This allows another equipment to probe the port and verify that it is still listening, without forwarding the connection to a remote server. In HTTP mode, a connection coming from a source matching <source> will be accepted, the following response will be sent without waiting for a request, then the connection will be closed : "HTTP/1.0 200 OK". This is normally enough for any front-end HTTP probe to detect that the service is UP and running without forwarding the request to a backend server. Note that this response is sent in raw format, without any transformation. This is important as it means that it will not be SSL-encrypted on SSL listeners. Monitor requests are processed very early, just after tcp-request connection ACLs which are the only ones able to block them. These connections are short lived and never wait for any data from the client. They cannot be logged, and it is the intended purpose. They are only used to report HAProxy's health to an upper component, nothing more. Please note that "monitor fail" rules do not apply to connections intercepted by "monitor-net". Last, please note that only one "monitor-net" statement can be specified in a frontend. If more than one is found, only the last one will be considered.
Example :
# addresses .252 and .253 are just probing us.
frontend www
monitor-net 192.168.0.252/31
See also : "monitor fail", "monitor-uri"
Intercept a URI used by external components' monitor requests
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<uri> is the exact URI which we want to intercept to return HAProxy's
health status instead of forwarding the request.
When an HTTP request referencing <uri> will be received on a frontend, HAProxy will not forward it nor log it, but instead will return either "HTTP/1.0 200 OK" or "HTTP/1.0 503 Service unavailable", depending on failure conditions defined with "monitor fail". This is normally enough for any front-end HTTP probe to detect that the service is UP and running without forwarding the request to a backend server. Note that the HTTP method, the version and all headers are ignored, but the request must at least be valid at the HTTP level. This keyword may only be used with an HTTP-mode frontend. Monitor requests are processed very early. It is not possible to block nor divert them using ACLs. They cannot be logged either, and it is the intended purpose. They are only used to report HAProxy's health to an upper component, nothing more. However, it is possible to add any number of conditions using "monitor fail" and ACLs so that the result can be adjusted to whatever check can be imagined (most often the number of available servers in a backend).
Example :
# Use /haproxy_test to report haproxy's status
frontend www
mode http
monitor-uri /haproxy_test
See also : "monitor fail", "monitor-net"
Enable or disable early dropping of aborted requests pending in queues.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
In presence of very high loads, the servers will take some time to respond. The per-instance connection queue will inflate, and the response time will increase respective to the size of the queue times the average per-session response time. When clients will wait for more than a few seconds, they will often hit the "STOP" button on their browser, leaving a useless request in the queue, and slowing down other users, and the servers as well, because the request will eventually be served, then aborted at the first error encountered while delivering the response. As there is no way to distinguish between a full STOP and a simple output close on the client side, HTTP agents should be conservative and consider that the client might only have closed its output channel while waiting for the response. However, this introduces risks of congestion when lots of users do the same, and is completely useless nowadays because probably no client at all will close the session while waiting for the response. Some HTTP agents support this behaviour (Squid, Apache, HAProxy), and others do not (TUX, most hardware-based load balancers). So the probability for a closed input channel to represent a user hitting the "STOP" button is close to 100%, and the risk of being the single component to break rare but valid traffic is extremely low, which adds to the temptation to be able to abort a session early while still not served and not pollute the servers. In HAProxy, the user can choose the desired behaviour using the option "abortonclose". By default (without the option) the behaviour is HTTP compliant and aborted requests will be served. But when the option is specified, a session with an incoming channel closed will be aborted while it is still possible, either pending in the queue for a connection slot, or during the connection establishment if the server has not yet acknowledged the connection request. This considerably reduces the queue size and the load on saturated servers when users are tempted to click on STOP, which in turn reduces the response time for other users. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
Enable or disable relaxing of HTTP request parsing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
By default, HAProxy complies with RFC2616 in terms of message parsing. This
means that invalid characters in header names are not permitted and cause an
error to be returned to the client. This is the desired behaviour as such
forbidden characters are essentially used to build attacks exploiting server
weaknesses, and bypass security filtering. Sometimes, a buggy browser or
server will emit invalid header names for whatever reason (configuration,
implementation) and the issue will not be immediately fixed. In such a case,
it is possible to relax HAProxy's header name parser to accept any character
even if that does not make sense, by specifying this option. Similarly, the
list of characters allowed to appear in a URI is well defined by RFC3986, and
chars 0-31, 32 (space), 34 ('"'), 60 ('<'), 62 ('>'), 92 ('\'), 94 ('^'), 96
('`'), 123 ('{'), 124 ('|'), 125 ('}'), 127 (delete) and anything above are
not allowed at all. Haproxy always blocks a number of them (0..32, 127). The
remaining ones are blocked by default unless this option is enabled.
This option should never be enabled by default as it hides application bugs
and open security breaches. It should only be deployed after a problem has
been confirmed.
When this option is enabled, erroneous header names will still be accepted in
requests, but the complete request will be captured in order to permit later
analysis using the "show errors" request on the UNIX stats socket. Similarly,
requests containing invalid chars in the URI part will be logged. Doing this
also helps confirming that the issue has been solved.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.See also : "option accept-invalid-http-response" and "show errors" on the stats socket.
Enable or disable relaxing of HTTP response parsing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
By default, HAProxy complies with RFC2616 in terms of message parsing. This means that invalid characters in header names are not permitted and cause an error to be returned to the client. This is the desired behaviour as such forbidden characters are essentially used to build attacks exploiting server weaknesses, and bypass security filtering. Sometimes, a buggy browser or server will emit invalid header names for whatever reason (configuration, implementation) and the issue will not be immediately fixed. In such a case, it is possible to relax HAProxy's header name parser to accept any character even if that does not make sense, by specifying this option. This option should never be enabled by default as it hides application bugs and open security breaches. It should only be deployed after a problem has been confirmed. When this option is enabled, erroneous header names will still be accepted in responses, but the complete response will be captured in order to permit later analysis using the "show errors" request on the UNIX stats socket. Doing this also helps confirming that the issue has been solved. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option accept-invalid-http-request" and "show errors" on the stats socket.
Use either all backup servers at a time or only the first one
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
By default, the first operational backup server gets all traffic when normal servers are all down. Sometimes, it may be preferred to use multiple backups at once, because one will not be enough. When "option allbackups" is enabled, the load balancing will be performed among all backup servers when all normal ones are unavailable. The same load balancing algorithm will be used and the servers' weights will be respected. Thus, there will not be any priority order between the backup servers anymore. This option is mostly used with static server farms dedicated to return a "sorry" page when an application is completely offline. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
Analyze all server responses and block requests with cacheable cookies
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
Some high-level frameworks set application cookies everywhere and do not always let enough control to the developer to manage how the responses should be cached. When a session cookie is returned on a cacheable object, there is a high risk of session crossing or stealing between users traversing the same caches. In some situations, it is better to block the response than to let some sensitive session information go in the wild. The option "checkcache" enables deep inspection of all server responses for strict compliance with HTTP specification in terms of cacheability. It carefully checks "Cache-control", "Pragma" and "Set-cookie" headers in server response to check if there's a risk of caching a cookie on a client-side proxy. When this option is enabled, the only responses which can be delivered to the client are : - all those without "Set-Cookie" header ; - all those with a return code other than 200, 203, 206, 300, 301, 410, provided that the server has not set a "Cache-control: public" header ; - all those that come from a POST request, provided that the server has not set a 'Cache-Control: public' header ; - those with a 'Pragma: no-cache' header - those with a 'Cache-control: private' header - those with a 'Cache-control: no-store' header - those with a 'Cache-control: max-age=0' header - those with a 'Cache-control: s-maxage=0' header - those with a 'Cache-control: no-cache' header - those with a 'Cache-control: no-cache="set-cookie"' header - those with a 'Cache-control: no-cache="set-cookie,' header (allowing other fields after set-cookie) If a response doesn't respect these requirements, then it will be blocked just as if it was from an "rspdeny" filter, with an "HTTP 502 bad gateway". The session state shows "PH--" meaning that the proxy blocked the response during headers processing. Additionally, an alert will be sent in the logs so that admins are informed that there's something to be fixed. Due to the high impact on the application, the application should be tested in depth with the option enabled before going to production. It is also a good practice to always activate it during tests, even if it is not used in production, as it will report potentially dangerous application behaviours. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
Enable or disable the sending of TCP keepalive packets on the client side
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
When there is a firewall or any session-aware component between a client and a server, and when the protocol involves very long sessions with long idle periods (eg: remote desktops), there is a risk that one of the intermediate components decides to expire a session which has remained idle for too long. Enabling socket-level TCP keep-alives makes the system regularly send packets to the other end of the connection, leaving it active. The delay between keep-alive probes is controlled by the system only and depends both on the operating system and its tuning parameters. It is important to understand that keep-alive packets are neither emitted nor received at the application level. It is only the network stacks which sees them. For this reason, even if one side of the proxy already uses keep-alives to maintain its connection alive, those keep-alive packets will not be forwarded to the other side of the proxy. Please note that this has nothing to do with HTTP keep-alive. Using option "clitcpka" enables the emission of TCP keep-alive probes on the client side of a connection, which should help when session expirations are noticed between HAProxy and a client. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option srvtcpka", "option tcpka"
Enable continuous traffic statistics updates
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
By default, counters used for statistics calculation are incremented only when a session finishes. It works quite well when serving small objects, but with big ones (for example large images or archives) or with A/V streaming, a graph generated from haproxy counters looks like a hedgehog. With this option enabled counters get incremented continuously, during a whole session. Recounting touches a hotpath directly so it is not enabled by default, as it has small performance impact (~0.5%).
Enable or disable logging of normal, successful connections
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
There are large sites dealing with several thousand connections per second and for which logging is a major pain. Some of them are even forced to turn logs off and cannot debug production issues. Setting this option ensures that normal connections, those which experience no error, no timeout, no retry nor redispatch, will not be logged. This leaves disk space for anomalies. In HTTP mode, the response status code is checked and return codes 5xx will still be logged. It is strongly discouraged to use this option as most of the time, the key to complex issues is in the normal logs which will not be logged here. If you need to separate logs, see the "log-separate-errors" option instead.
Enable or disable logging of null connections
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
In certain environments, there are components which will regularly connect to various systems to ensure that they are still alive. It can be the case from another load balancer as well as from monitoring systems. By default, even a simple port probe or scan will produce a log. If those connections pollute the logs too much, it is possible to enable option "dontlognull" to indicate that a connection on which no data has been transferred will not be logged, which typically corresponds to those probes. It is generally recommended not to use this option in uncontrolled environments (eg: internet), otherwise scans and other malicious activities would not be logged. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
Enable or disable active connection closing after response is transferred.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
Some HTTP servers do not necessarily close the connections when they receive the "Connection: close" set by "option httpclose", and if the client does not close either, then the connection remains open till the timeout expires. This causes high number of simultaneous connections on the servers and shows high global session times in the logs. When this happens, it is possible to use "option forceclose". It will actively close the outgoing server channel as soon as the server has finished to respond. This option implicitly enables the "httpclose" option. Note that this option also enables the parsing of the full request and response, which means we can close the connection to the server very quickly, releasing some resources earlier than with httpclose. This option may also be combined with "option http-pretend-keepalive", which will disable sending of the "Connection: close" header, but will still cause the connection to be closed once the whole response is received. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option httpclose" and "option http-pretend-keepalive"
Enable insertion of the X-Forwarded-For header to requests sent to servers
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<network> is an optional argument used to disable this option for sources
matching <network>
<name> an optional argument to specify a different "X-Forwarded-For"
header name.
Since HAProxy works in reverse-proxy mode, the servers see its IP address as their client address. This is sometimes annoying when the client's IP address is expected in server logs. To solve this problem, the well-known HTTP header "X-Forwarded-For" may be added by HAProxy to all requests sent to the server. This header contains a value representing the client's IP address. Since this header is always appended at the end of the existing header list, the server must be configured to always use the last occurrence of this header only. See the server's manual to find how to enable use of this standard header. Note that only the last occurrence of the header must be used, since it is really possible that the client has already brought one. The keyword "header" may be used to supply a different header name to replace the default "X-Forwarded-For". This can be useful where you might already have a "X-Forwarded-For" header from a different application (eg: stunnel), and you need preserve it. Also if your backend server doesn't use the "X-Forwarded-For" header and requires different one (eg: Zeus Web Servers require "X-Cluster-Client-IP"). Sometimes, a same HAProxy instance may be shared between a direct client access and a reverse-proxy access (for instance when an SSL reverse-proxy is used to decrypt HTTPS traffic). It is possible to disable the addition of the header for a known source address or network by adding the "except" keyword followed by the network address. In this case, any source IP matching the network will not cause an addition of this header. Most common uses are with private networks or 127.0.0.1. Alternatively, the keyword "if-none" states that the header will only be added if it is not present. This should only be used in perfectly trusted environment, as this might cause a security issue if headers reaching haproxy are under the control of the end-user. This option may be specified either in the frontend or in the backend. If at least one of them uses it, the header will be added. Note that the backend's setting of the header subargument takes precedence over the frontend's if both are defined. In the case of the "if-none" argument, if at least one of the frontend or the backend does not specify it, it wants the addition to be mandatory, so it wins. It is important to note that by default, HAProxy works in tunnel mode and only inspects the first request of a connection, meaning that only the first request will have the header appended, which is certainly not what you want. In order to fix this, ensure that any of the "httpclose", "forceclose" or "http-server-close" options is set when using this option.
Examples :
# Public HTTP address also used by stunnel on the same machine
frontend www
mode http
option forwardfor except 127.0.0.1 # stunnel already adds the header
# Those servers want the IP Address in X-Client
backend www
mode http
option forwardfor header X-Client
Instruct the system to favor low interactive delays over performance in HTTP
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
In HTTP, each payload is unidirectional and has no notion of interactivity. Any agent is expected to queue data somewhat for a reasonably low delay. There are some very rare server-to-server applications that abuse the HTTP protocol and expect the payload phase to be highly interactive, with many interleaved data chunks in both directions within a single request. This is absolutely not supported by the HTTP specification and will not work across most proxies or servers. When such applications attempt to do this through haproxy, it works but they will experience high delays due to the network optimizations which favor performance by instructing the system to wait for enough data to be available in order to only send full packets. Typical delays are around 200 ms per round trip. Note that this only happens with abnormal uses. Normal uses such as CONNECT requests nor WebSockets are not affected. When "option http-no-delay" is present in either the frontend or the backend used by a connection, all such optimizations will be disabled in order to make the exchanges as fast as possible. Of course this offers no guarantee on the functionality, as it may break at any other place. But if it works via HAProxy, it will work as fast as possible. This option should never be used by default, and should never be used at all unless such a buggy application is discovered. The impact of using this option is an increase of bandwidth usage and CPU usage, which may significantly lower performance in high latency environments.
Define whether haproxy will announce keepalive to the server or not
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
When running with "option http-server-close" or "option forceclose", haproxy adds a "Connection: close" header to the request forwarded to the server. Unfortunately, when some servers see this header, they automatically refrain from using the chunked encoding for responses of unknown length, while this is totally unrelated. The immediate effect is that this prevents haproxy from maintaining the client connection alive. A second effect is that a client or a cache could receive an incomplete response without being aware of it, and consider the response complete. By setting "option http-pretend-keepalive", haproxy will make the server believe it will keep the connection alive. The server will then not fall back to the abnormal undesired above. When haproxy gets the whole response, it will close the connection with the server just as it would do with the "forceclose" option. That way the client gets a normal response and the connection is correctly closed on the server side. It is recommended not to enable this option by default, because most servers will more efficiently close the connection themselves after the last packet, and release its buffers slightly earlier. Also, the added packet on the network could slightly reduce the overall peak performance. However it is worth noting that when this option is enabled, haproxy will have slightly less work to do. So if haproxy is the bottleneck on the whole architecture, enabling this option might save a few CPU cycles. This option may be set both in a frontend and in a backend. It is enabled if at least one of the frontend or backend holding a connection has it enabled. This option may be combined with "option httpclose", which will cause keepalive to be announced to the server and close to be announced to the client. This practice is discouraged though. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option forceclose" and "option http-server-close"
Enable or disable HTTP connection closing on the server side
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
By default, when a client communicates with a server, HAProxy will only analyze, log, and process the first request of each connection. Setting "option http-server-close" enables HTTP connection-close mode on the server side while keeping the ability to support HTTP keep-alive and pipelining on the client side. This provides the lowest latency on the client side (slow network) and the fastest session reuse on the server side to save server resources, similarly to "option forceclose". It also permits non-keepalive capable servers to be served in keep-alive mode to the clients if they conform to the requirements of RFC2616. Please note that some servers do not always conform to those requirements when they see "Connection: close" in the request. The effect will be that keep-alive will never be used. A workaround consists in enabling "option http-pretend-keepalive". At the moment, logs will not indicate whether requests came from the same session or not. The accept date reported in the logs corresponds to the end of the previous request, and the request time corresponds to the time spent waiting for a new request. The keep-alive request time is still bound to the timeout defined by "timeout http-keep-alive" or "timeout http-request" if not set. This option may be set both in a frontend and in a backend. It is enabled if at least one of the frontend or backend holding a connection has it enabled. It is worth noting that "option forceclose" has precedence over "option http-server-close" and that combining "http-server-close" with "httpclose" basically achieve the same result as "forceclose". If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option forceclose", "option http-pretend-keepalive", "option httpclose" and "1.1. The HTTP transaction model".
Make use of non-standard Proxy-Connection header instead of Connection
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
While RFC2616 explicitly states that HTTP/1.1 agents must use the Connection header to indicate their wish of persistent or non-persistent connections, both browsers and proxies ignore this header for proxied connections and make use of the undocumented, non-standard Proxy-Connection header instead. The issue begins when trying to put a load balancer between browsers and such proxies, because there will be a difference between what haproxy understands and what the client and the proxy agree on. By setting this option in a frontend, haproxy can automatically switch to use that non-standard header if it sees proxied requests. A proxied request is defined here as one where the URI begins with neither a '/' nor a '*'. The choice of header only affects requests passing through proxies making use of one of the "httpclose", "forceclose" and "http-server-close" options. Note that this option can only be specified in a frontend and will affect the request along its whole life. Also, when this option is set, a request which requires authentication will automatically switch to use proxy authentication headers if it is itself a proxied request. That makes it possible to check or enforce authentication in front of an existing proxy. This option should normally never be used, except in front of a proxy.
Enable HTTP protocol to check on the servers health
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<method> is the optional HTTP method used with the requests. When not set,
the "OPTIONS" method is used, as it generally requires low server
processing and is easy to filter out from the logs. Any method
may be used, though it is not recommended to invent non-standard
ones.
<uri> is the URI referenced in the HTTP requests. It defaults to " / "
which is accessible by default on almost any server, but may be
changed to any other URI. Query strings are permitted.
<version> is the optional HTTP version string. It defaults to "HTTP/1.0"
but some servers might behave incorrectly in HTTP 1.0, so turning
it to HTTP/1.1 may sometimes help. Note that the Host field is
mandatory in HTTP/1.1, and as a trick, it is possible to pass it
after "\r\n" following the version string.
By default, server health checks only consist in trying to establish a TCP connection. When "option httpchk" is specified, a complete HTTP request is sent once the TCP connection is established, and responses 2xx and 3xx are considered valid, while all other ones indicate a server failure, including the lack of any response. The port and interval are specified in the server configuration. This option does not necessarily require an HTTP backend, it also works with plain TCP backends. This is particularly useful to check simple scripts bound to some dedicated ports using the inetd daemon.
Examples :
# Relay HTTPS traffic to Apache instance and check service availability
# using HTTP request "OPTIONS * HTTP/1.1" on port 80.
backend https_relay
mode tcp
option httpchk OPTIONS * HTTP/1.1\r\nHost:\ www
server apache1 192.168.1.1:443 check port 80
See also : "option lb-agent-chk", "option ssl-hello-chk", "option smtpchk", "option mysql-check", "option pgsql-check", "http-check" and the "check", "port" and "inter" server options.
Enable or disable passive HTTP connection closing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
By default, when a client communicates with a server, HAProxy will only analyze, log, and process the first request of each connection. If "option httpclose" is set, it will check if a "Connection: close" header is already set in each direction, and will add one if missing. Each end should react to this by actively closing the TCP connection after each transfer, thus resulting in a switch to the HTTP close mode. Any "Connection" header different from "close" will also be removed. It seldom happens that some servers incorrectly ignore this header and do not close the connection even though they reply "Connection: close". For this reason, they are not compatible with older HTTP 1.0 browsers. If this happens it is possible to use the "option forceclose" which actively closes the request connection once the server responds. Option "forceclose" also releases the server connection earlier because it does not have to wait for the client to acknowledge it. This option may be set both in a frontend and in a backend. It is enabled if at least one of the frontend or backend holding a connection has it enabled. If "option forceclose" is specified too, it has precedence over "httpclose". If "option http-server-close" is enabled at the same time as "httpclose", it basically achieves the same result as "option forceclose". If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option forceclose", "option http-server-close" and "1.1. The HTTP transaction model".
Enable logging of HTTP request, session state and timers
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
clf if the "clf" argument is added, then the output format will be
the CLF format instead of HAProxy's default HTTP format. You can
use this when you need to feed HAProxy's logs through a specific
log analyser which only support the CLF format and which is not
extensible.
By default, the log output format is very poor, as it only contains the source and destination addresses, and the instance name. By specifying "option httplog", each log line turns into a much richer format including, but not limited to, the HTTP request, the connection timers, the session status, the connections numbers, the captured headers and cookies, the frontend, backend and server name, and of course the source address and ports. This option may be set either in the frontend or the backend. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. Specifying only "option httplog" will automatically clear the 'clf' mode if it was set by default.
See also : section 8 about logging.
Enable or disable plain HTTP proxy mode
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
It sometimes happens that people need a pure HTTP proxy which understands basic proxy requests without caching nor any fancy feature. In this case, it may be worth setting up an HAProxy instance with the "option http_proxy" set. In this mode, no server is declared, and the connection is forwarded to the IP address and port found in the URL after the "http://" scheme. No host address resolution is performed, so this only works when pure IP addresses are passed. Since this option's usage perimeter is rather limited, it will probably be used only by experts who know they need exactly it. Last, if the clients are susceptible of sending keep-alive requests, it will be needed to add "option httpclose" to ensure that all requests will correctly be analyzed. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
Example :
# this backend understands HTTP proxy requests and forwards them directly.
backend direct_forward
option httpclose
option http_proxy
See also : "option httpclose"
Enable or disable independent timeout processing for both directions
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
By default, when data is sent over a socket, both the write timeout and the
read timeout for that socket are refreshed, because we consider that there is
activity on that socket, and we have no other means of guessing if we should
receive data or not.
While this default behaviour is desirable for almost all applications, there
exists a situation where it is desirable to disable it, and only refresh the
read timeout if there are incoming data. This happens on sessions with large
timeouts and low amounts of exchanged data such as telnet session. If the
server suddenly disappears, the output data accumulates in the system's
socket buffers, both timeouts are correctly refreshed, and there is no way
to know the server does not receive them, so we don't timeout. However, when
the underlying protocol always echoes sent data, it would be enough by itself
to detect the issue using the read timeout. Note that this problem does not
happen with more verbose protocols because data won't accumulate long in the
socket buffers.
When this option is set on the frontend, it will disable read timeout updates
on data sent to the client. There probably is little use of this case. When
the option is set on the backend, it will disable read timeout updates on
data sent to the server. Doing so will typically break large HTTP posts from
slow lines, so use it with caution.
Note: older versions used to call this setting "option independant-streams"
with a spelling mistake. This spelling is still supported but
deprecated.
Use a TCP connection to obtain a metric of server health
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
This alters health checking behaviour by connecting making a TCP connection and reading an ASCII string. The string should have one of the following forms: * An ASCII representation of an positive integer percentage. e.g. "75%" Values in this format will set the weight proportional to the initial weight of a server as configured when haproxy starts. * The string "drain". This will cause the weight of a server to be set to 0, and thus it will not accept any new connections other than those that are accepted via persistence. * The string "down", optionally followed by a description string. Mark the server as down and log the description string as the reason. * The string "stopped", optionally followed by a description string. This currently has the same behaviour as down (iii). * The string "fail", optionally followed by a description string. This currently has the same behaviour as down (iii). The use of an alternate check-port, used to obtain agent heath check information described above as opposed to the port of the service, may be useful in conjunction with this option.
Use LDAPv3 health checks for server testing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
It is possible to test that the server correctly talks LDAPv3 instead of just testing that it accepts the TCP connection. When this option is set, an LDAPv3 anonymous simple bind message is sent to the server, and the response is analyzed to find an LDAPv3 bind response message. The server is considered valid only when the LDAP response contains success resultCode (http://tools.ietf.org/html/rfc4511#section-4.1.9). Logging of bind requests is server dependent see your documentation how to configure it.
Example :
option ldap-check
See also : "option httpchk"
Enable or disable logging of health checks
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
Enable health checks logging so it possible to check for example what was happening before a server crash. Failed health check are logged if server is UP and succeeded health checks if server is DOWN, so the amount of additional information is limited. If health check logging is enabled no health check status is printed when servers is set up UP/DOWN/ENABLED/DISABLED.
Change log level for non-completely successful connections
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
Sometimes looking for errors in logs is not easy. This option makes haproxy raise the level of logs containing potentially interesting information such as errors, timeouts, retries, redispatches, or HTTP status codes 5xx. The level changes from "info" to "err". This makes it possible to log them separately to a different file with most syslog daemons. Be careful not to remove them from the original file, otherwise you would lose ordering which provides very important information. Using this option, large sites dealing with several thousand connections per second may log normal traffic to a rotating buffer and only archive smaller error logs.
Enable or disable early logging of HTTP requests
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
By default, HTTP requests are logged upon termination so that the total transfer time and the number of bytes appear in the logs. When large objects are being transferred, it may take a while before the request appears in the logs. Using "option logasap", the request gets logged as soon as the server sends the complete headers. The only missing information in the logs will be the total number of bytes which will indicate everything except the amount of data transferred, and the total time which will not take the transfer time into account. In such a situation, it's a good practice to capture the "Content-Length" response header so that the logs at least indicate how many bytes are expected to be transferred.
Examples :
listen http_proxy 0.0.0.0:80
mode http
option httplog
option logasap
log 192.168.2.200 local3
>>> Feb 6 12:14:14 localhost \
haproxy[14389]: 10.0.1.2:33317 [06/Feb/2009:12:14:14.655] http-in \
static/srv1 9/10/7/14/+30 200 +243 - - ---- 3/1/1/1/0 1/0 \
"GET /image.iso HTTP/1.0"
Use MySQL health checks for server testing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<username> This is the username which will be used when connecting to MySQL
server.
If you specify a username, the check consists of sending two MySQL packet,
one Client Authentication packet, and one QUIT packet, to correctly close
MySQL session. We then parse the MySQL Handshake Initialisation packet and/or
Error packet. It is a basic but useful test which does not produce error nor
aborted connect on the server. However, it requires adding an authorization
in the MySQL table, like this :
USE mysql;
INSERT INTO user (Host,User) values ('<ip_of_haproxy>','<username>');
FLUSH PRIVILEGES;
If you don't specify a username (it is deprecated and not recommended), the
check only consists in parsing the Mysql Handshake Initialisation packet or
Error packet, we don't send anything in this mode. It was reported that it
can generate lockout if check is too frequent and/or if there is not enough
traffic. In fact, you need in this case to check MySQL "max_connect_errors"
value as if a connection is established successfully within fewer than MySQL
"max_connect_errors" attempts after a previous connection was interrupted,
the error count for the host is cleared to zero. If HAProxy's server get
blocked, the "FLUSH HOSTS" statement is the only way to unblock it.
Remember that this does not check database presence nor database consistency.
To do this, you can use an external check with xinetd for example.
The check requires MySQL >=3.22, for older version, please use TCP check.
Most often, an incoming MySQL server needs to see the client's IP address for
various purposes, including IP privilege matching and connection logging.
When possible, it is often wise to masquerade the client's IP address when
connecting to the server using the "usesrc" argument of the "source" keyword,
which requires the cttproxy feature to be compiled in, and the MySQL server
to route the client via the machine hosting haproxy.See also: "option httpchk"
Use PostgreSQL health checks for server testing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<username> This is the username which will be used when connecting to
PostgreSQL server.
The check sends a PostgreSQL StartupMessage and waits for either Authentication request or ErrorResponse message. It is a basic but useful test which does not produce error nor aborted connect on the server. This check is identical with the "mysql-check".
See also: "option httpchk"
Enable or disable immediate session resource cleaning after close
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
When clients or servers abort connections in a dirty way (eg: they are physically disconnected), the session timeouts triggers and the session is closed. But it will remain in FIN_WAIT1 state for some time in the system, using some resources and possibly limiting the ability to establish newer connections. When this happens, it is possible to activate "option nolinger" which forces the system to immediately remove any socket's pending data on close. Thus, the session is instantly purged from the system's tables. This usually has side effects such as increased number of TCP resets due to old retransmits getting immediately rejected. Some firewalls may sometimes complain about this too. For this reason, it is not recommended to use this option when not absolutely needed. You know that you need it when you have thousands of FIN_WAIT1 sessions on your system (TIME_WAIT ones do not count). This option may be used both on frontends and backends, depending on the side where it is required. Use it on the frontend for clients, and on the backend for servers. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
Enable insertion of the X-Original-To header to requests sent to servers
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<network> is an optional argument used to disable this option for sources
matching <network>
<name> an optional argument to specify a different "X-Original-To"
header name.
Since HAProxy can work in transparent mode, every request from a client can be redirected to the proxy and HAProxy itself can proxy every request to a complex SQUID environment and the destination host from SO_ORIGINAL_DST will be lost. This is annoying when you want access rules based on destination ip addresses. To solve this problem, a new HTTP header "X-Original-To" may be added by HAProxy to all requests sent to the server. This header contains a value representing the original destination IP address. Since this must be configured to always use the last occurrence of this header only. Note that only the last occurrence of the header must be used, since it is really possible that the client has already brought one. The keyword "header" may be used to supply a different header name to replace the default "X-Original-To". This can be useful where you might already have a "X-Original-To" header from a different application, and you need preserve it. Also if your backend server doesn't use the "X-Original-To" header and requires different one. Sometimes, a same HAProxy instance may be shared between a direct client access and a reverse-proxy access (for instance when an SSL reverse-proxy is used to decrypt HTTPS traffic). It is possible to disable the addition of the header for a known source address or network by adding the "except" keyword followed by the network address. In this case, any source IP matching the network will not cause an addition of this header. Most common uses are with private networks or 127.0.0.1. This option may be specified either in the frontend or in the backend. If at least one of them uses it, the header will be added. Note that the backend's setting of the header subargument takes precedence over the frontend's if both are defined. It is important to note that by default, HAProxy works in tunnel mode and only inspects the first request of a connection, meaning that only the first request will have the header appended, which is certainly not what you want. In order to fix this, ensure that any of the "httpclose", "forceclose" or "http-server-close" options is set when using this option.
Examples :
# Original Destination address
frontend www
mode http
option originalto except 127.0.0.1
# Those servers want the IP Address in X-Client-Dst
backend www
mode http
option originalto header X-Client-Dst
Enable or disable forced persistence on down servers
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
When an HTTP request reaches a backend with a cookie which references a dead server, by default it is redispatched to another server. It is possible to force the request to be sent to the dead server first using "option persist" if absolutely needed. A common use case is when servers are under extreme load and spend their time flapping. In this case, the users would still be directed to the server they opened the session on, in the hope they would be correctly served. It is recommended to use "option redispatch" in conjunction with this option so that in the event it would not be possible to connect to the server at all (server definitely dead), the client would finally be redirected to another valid server. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
Enable or disable session redistribution in case of connection failure
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
In HTTP mode, if a server designated by a cookie is down, clients may definitely stick to it because they cannot flush the cookie, so they will not be able to access the service anymore. Specifying "option redispatch" will allow the proxy to break their persistence and redistribute them to a working server. It also allows to retry last connection to another server in case of multiple connection failures. Of course, it requires having "retries" set to a nonzero value. This form is the preferred form, which replaces both the "redispatch" and "redisp" keywords. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
Use redis health checks for server testing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
It is possible to test that the server correctly talks REDIS protocol instead of just testing that it accepts the TCP connection. When this option is set, a PING redis command is sent to the server, and the response is analyzed to find the "+PONG" response message.
Example :
option redis-check
See also : "option httpchk"
Use SMTP health checks for server testing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<hello> is an optional argument. It is the "hello" command to use. It can
be either "HELO" (for SMTP) or "EHLO" (for ESTMP). All other
values will be turned into the default command ("HELO").
<domain> is the domain name to present to the server. It may only be
specified (and is mandatory) if the hello command has been
specified. By default, "localhost" is used.
When "option smtpchk" is set, the health checks will consist in TCP connections followed by an SMTP command. By default, this command is "HELO localhost". The server's return code is analyzed and only return codes starting with a "2" will be considered as valid. All other responses, including a lack of response will constitute an error and will indicate a dead server. This test is meant to be used with SMTP servers or relays. Depending on the request, it is possible that some servers do not log each connection attempt, so you may want to experiment to improve the behaviour. Using telnet on port 25 is often easier than adjusting the configuration. Most often, an incoming SMTP server needs to see the client's IP address for various purposes, including spam filtering, anti-spoofing and logging. When possible, it is often wise to masquerade the client's IP address when connecting to the server using the "usesrc" argument of the "source" keyword, which requires the cttproxy feature to be compiled in.
Example :
option smtpchk HELO mydomain.org
See also : "option httpchk", "source"
Enable or disable collecting & providing separate statistics for each socket.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
Enable or disable automatic kernel acceleration on sockets in both directions
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
When this option is enabled either on a frontend or on a backend, haproxy will automatically evaluate the opportunity to use kernel tcp splicing to forward data between the client and the server, in either direction. Haproxy uses heuristics to estimate if kernel splicing might improve performance or not. Both directions are handled independently. Note that the heuristics used are not much aggressive in order to limit excessive use of splicing. This option requires splicing to be enabled at compile time, and may be globally disabled with the global option "nosplice". Since splice uses pipes, using it requires that there are enough spare pipes. Important note: kernel-based TCP splicing is a Linux-specific feature which first appeared in kernel 2.6.25. It offers kernel-based acceleration to transfer data between sockets without copying these data to user-space, thus providing noticeable performance gains and CPU cycles savings. Since many early implementations are buggy, corrupt data and/or are inefficient, this feature is not enabled by default, and it should be used with extreme care. While it is not possible to detect the correctness of an implementation, 2.6.29 is the first version offering a properly working implementation. In case of doubt, splicing may be globally disabled using the global "nosplice" keyword.
Example :
option splice-auto
If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option splice-request", "option splice-response", and global options "nosplice" and "maxpipes"
Enable or disable automatic kernel acceleration on sockets for requests
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
When this option is enabled either on a frontend or on a backend, haproxy will use kernel tcp splicing whenever possible to forward data going from the client to the server. It might still use the recv/send scheme if there are no spare pipes left. This option requires splicing to be enabled at compile time, and may be globally disabled with the global option "nosplice". Since splice uses pipes, using it requires that there are enough spare pipes. Important note: see "option splice-auto" for usage limitations.
Example :
option splice-request
If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option splice-auto", "option splice-response", and global options "nosplice" and "maxpipes"
Enable or disable automatic kernel acceleration on sockets for responses
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
When this option is enabled either on a frontend or on a backend, haproxy will use kernel tcp splicing whenever possible to forward data going from the server to the client. It might still use the recv/send scheme if there are no spare pipes left. This option requires splicing to be enabled at compile time, and may be globally disabled with the global option "nosplice". Since splice uses pipes, using it requires that there are enough spare pipes. Important note: see "option splice-auto" for usage limitations.
Example :
option splice-response
If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option splice-auto", "option splice-request", and global options "nosplice" and "maxpipes"
Enable or disable the sending of TCP keepalive packets on the server side
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
When there is a firewall or any session-aware component between a client and a server, and when the protocol involves very long sessions with long idle periods (eg: remote desktops), there is a risk that one of the intermediate components decides to expire a session which has remained idle for too long. Enabling socket-level TCP keep-alives makes the system regularly send packets to the other end of the connection, leaving it active. The delay between keep-alive probes is controlled by the system only and depends both on the operating system and its tuning parameters. It is important to understand that keep-alive packets are neither emitted nor received at the application level. It is only the network stacks which sees them. For this reason, even if one side of the proxy already uses keep-alives to maintain its connection alive, those keep-alive packets will not be forwarded to the other side of the proxy. Please note that this has nothing to do with HTTP keep-alive. Using option "srvtcpka" enables the emission of TCP keep-alive probes on the server side of a connection, which should help when session expirations are noticed between HAProxy and a server. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option clitcpka", "option tcpka"
Use SSLv3 client hello health checks for server testing
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
When some SSL-based protocols are relayed in TCP mode through HAProxy, it is possible to test that the server correctly talks SSL instead of just testing that it accepts the TCP connection. When "option ssl-hello-chk" is set, pure SSLv3 client hello messages are sent once the connection is established to the server, and the response is analyzed to find an SSL server hello message. The server is considered valid only when the response contains this server hello message. All servers tested till there correctly reply to SSLv3 client hello messages, and most servers tested do not even log the requests containing only hello messages, which is appreciable. Note that this check works even when SSL support was not built into haproxy because it forges the SSL message. When SSL support is available, it is best to use native SSL health checks instead of this one.
See also: "option httpchk", "check-ssl"
Enable or disable the saving of one ACK packet during the accept sequence
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments : none
When an HTTP connection request comes in, the system acknowledges it on behalf of HAProxy, then the client immediately sends its request, and the system acknowledges it too while it is notifying HAProxy about the new connection. HAProxy then reads the request and responds. This means that we have one TCP ACK sent by the system for nothing, because the request could very well be acknowledged by HAProxy when it sends its response. For this reason, in HTTP mode, HAProxy automatically asks the system to avoid sending this useless ACK on platforms which support it (currently at least Linux). It must not cause any problem, because the system will send it anyway after 40 ms if the response takes more time than expected to come. During complex network debugging sessions, it may be desirable to disable this optimization because delayed ACKs can make troubleshooting more complex when trying to identify where packets are delayed. It is then possible to fall back to normal behaviour by specifying "no option tcp-smart-accept". It is also possible to force it for non-HTTP proxies by simply specifying "option tcp-smart-accept". For instance, it can make sense with some services such as SMTP where the server speaks first. It is recommended to avoid forcing this option in a defaults section. In case of doubt, consider setting it back to automatic values by prepending the "default" keyword before it, or disabling it using the "no" keyword.
See also : "option tcp-smart-connect"
Enable or disable the saving of one ACK packet during the connect sequence
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
On certain systems (at least Linux), HAProxy can ask the kernel not to immediately send an empty ACK upon a connection request, but to directly send the buffer request instead. This saves one packet on the network and thus boosts performance. It can also be useful for some servers, because they immediately get the request along with the incoming connection. This feature is enabled when "option tcp-smart-connect" is set in a backend. It is not enabled by default because it makes network troubleshooting more complex. It only makes sense to enable it with protocols where the client speaks first such as HTTP. In other situations, if there is no data to send in place of the ACK, a normal ACK is sent. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it.
See also : "option tcp-smart-accept"
Enable or disable the sending of TCP keepalive packets on both sides
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
When there is a firewall or any session-aware component between a client and a server, and when the protocol involves very long sessions with long idle periods (eg: remote desktops), there is a risk that one of the intermediate components decides to expire a session which has remained idle for too long. Enabling socket-level TCP keep-alives makes the system regularly send packets to the other end of the connection, leaving it active. The delay between keep-alive probes is controlled by the system only and depends both on the operating system and its tuning parameters. It is important to understand that keep-alive packets are neither emitted nor received at the application level. It is only the network stacks which sees them. For this reason, even if one side of the proxy already uses keep-alives to maintain its connection alive, those keep-alive packets will not be forwarded to the other side of the proxy. Please note that this has nothing to do with HTTP keep-alive. Using option "tcpka" enables the emission of TCP keep-alive probes on both the client and server sides of a connection. Note that this is meaningful only in "defaults" or "listen" sections. If this option is used in a frontend, only the client side will get keep-alives, and if this option is used in a backend, only the server side will get keep-alives. For this reason, it is strongly recommended to explicitly use "option clitcpka" and "option srvtcpka" when the configuration is split between frontends and backends.
See also : "option clitcpka", "option srvtcpka"
Enable advanced logging of TCP connections with session state and timers
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments : none
By default, the log output format is very poor, as it only contains the source and destination addresses, and the instance name. By specifying "option tcplog", each log line turns into a much richer format including, but not limited to, the connection timers, the session status, the connections numbers, the frontend, backend and server name, and of course the source address and ports. This option is useful for pure TCP proxies in order to find which of the client or server disconnects or times out. For normal HTTP proxies, it's better to use "option httplog" which is even more complete. This option may be set either in the frontend or the backend.
See also : "option httplog", and section 8 about logging.
Enable client-side transparent proxying
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
This option was introduced in order to provide layer 7 persistence to layer 3 load balancers. The idea is to use the OS's ability to redirect an incoming connection for a remote address to a local process (here HAProxy), and let this process know what address was initially requested. When this option is used, sessions without cookies will be forwarded to the original destination IP address of the incoming request (which should match that of another equipment), while requests with cookies will still be forwarded to the appropriate server. Note that contrary to a common belief, this option does NOT make HAProxy present the client's IP to the server when establishing the connection.
See also: the "usesrc" argument of the "source" keyword, and the "transparent" option of the "bind" keyword.
Enable RDP cookie-based persistence
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<name> is the optional name of the RDP cookie to check. If omitted, the
default cookie name "msts" will be used. There currently is no
valid reason to change this name.
This statement enables persistence based on an RDP cookie. The RDP cookie contains all information required to find the server in the list of known servers. So when this option is set in the backend, the request is analysed and if an RDP cookie is found, it is decoded. If it matches a known server which is still UP (or if "option persist" is set), then the connection is forwarded to this server. Note that this only makes sense in a TCP backend, but for this to work, the frontend must have waited long enough to ensure that an RDP cookie is present in the request buffer. This is the same requirement as with the "rdp-cookie" load-balancing method. Thus it is highly recommended to put all statements in a single "listen" section. Also, it is important to understand that the terminal server will emit this RDP cookie only if it is configured for "token redirection mode", which means that the "IP address redirection" option is disabled.
Example :
listen tse-farm
bind :3389
# wait up to 5s for an RDP cookie in the request
tcp-request inspect-delay 5s
tcp-request content accept if RDP_COOKIE
# apply RDP cookie persistence
persist rdp-cookie
# if server is unknown, let's balance on the same cookie.
# alternatively, "balance leastconn" may be useful too.
balance rdp-cookie
server srv1 1.1.1.1:3389
server srv2 1.1.1.2:3389
See also : "balance rdp-cookie", "tcp-request", the "req_rdp_cookie" ACL and the rdp_cookie pattern fetch function.
Set a limit on the number of new sessions accepted per second on a frontend
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<rate> The <rate> parameter is an integer designating the maximum number
of new sessions per second to accept on the frontend.
When the frontend reaches the specified number of new sessions per second, it
stops accepting new connections until the rate drops below the limit again.
During this time, the pending sessions will be kept in the socket's backlog
(in system buffers) and haproxy will not even be aware that sessions are
pending. When applying very low limit on a highly loaded service, it may make
sense to increase the socket's backlog using the "backlog" keyword.
This feature is particularly efficient at blocking connection-based attacks
or service abuse on fragile servers. Since the session rate is measured every
millisecond, it is extremely accurate. Also, the limit applies immediately,
no delay is needed at all to detect the threshold.
Example :
Limit the connection rate on SMTP to 10 per second maxlisten smtp mode tcp bind :25 rate-limit sessions 10 server 127.0.0.1:1025
Note : when the maximum rate is reached, the frontend's status is not changed
but its sockets appear as "WAITING" in the statistics if the
"socket-stats" option is enabled.See also : the "backlog" keyword and the "fe_sess_rate" ACL criterion.
Return an HTTP redirection if/unless a condition is matched
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
If/unless the condition is matched, the HTTP request will lead to a redirect response. If no condition is specified, the redirect applies unconditionally.
Arguments :
<loc> With "redirect location", the exact value in <loc> is placed into the HTTP "Location" header. <pfx> With "redirect prefix", the "Location" header is built from the concatenation of <pfx> and the complete URI path, including the query string, unless the "drop-query" option is specified (see below). As a special case, if <pfx> equals exactly "/", then nothing is inserted before the original URI. It allows one to redirect to the same URL (for instance, to insert a cookie). <sch> With "redirect scheme", then the "Location" header is built by concatenating <sch> with "://" then the first occurrence of the "Host" header, and then the URI path, including the query string unless the "drop-query" option is specified (see below). If no path is found or if the path is "*", then "/" is used instead. If no "Host" header is found, then an empty host component will be returned, which most recent browsers interprete as redirecting to the same host. This directive is mostly used to redirect HTTP to HTTPS. <code> The code is optional. It indicates which type of HTTP redirection is desired. Only codes 301, 302, 303, 307 and 308 are supported, with 302 used by default if no code is specified. 301 means "Moved permanently", and a browser may cache the Location. 302 means "Moved permanently" and means that the browser should not cache the redirection. 303 is equivalent to 302 except that the browser will fetch the location with a GET method. 307 is just like 302 but makes it clear that the same method must be reused. Likewise, 308 replaces 301 if the same method must be used. <option> There are several options which can be specified to adjust the expected behaviour of a redirection : - "drop-query" When this keyword is used in a prefix-based redirection, then the location will be set without any possible query-string, which is useful for directing users to a non-secure page for instance. It has no effect with a location-type redirect. - "append-slash" This keyword may be used in conjunction with "drop-query" to redirect users who use a URL not ending with a '/' to the same one with the '/'. It can be useful to ensure that search engines will only see one URL. For this, a return code 301 is preferred. - "set-cookie NAME[=value]" A "Set-Cookie" header will be added with NAME (and optionally "=value") to the response. This is sometimes used to indicate that a user has been seen, for instance to protect against some types of DoS. No other cookie option is added, so the cookie will be a session cookie. Note that for a browser, a sole cookie name without an equal sign is different from a cookie with an equal sign. - "clear-cookie NAME[=]" A "Set-Cookie" header will be added with NAME (and optionally "="), but with the "Max-Age" attribute set to zero. This will tell the browser to delete this cookie. It is useful for instance on logout pages. It is important to note that clearing the cookie "NAME" will not remove a cookie set with "NAME=value". You have to clear the cookie "NAME=" for that, because the browser makes the difference.
Example:
Move the login URL only to HTTPS.acl clear dst_port 80 acl secure dst_port 8080 acl login_page url_beg /login acl logout url_beg /logout acl uid_given url_reg /login?userid=[^&]+ acl cookie_set hdr_sub(cookie) SEEN=1 redirect prefix https://mysite.com set-cookie SEEN=1 if !cookie_set redirect prefix https://mysite.com if login_page !secure redirect prefix http://mysite.com drop-query if login_page !uid_given redirect location http://mysite.com/ if !login_page secure redirect location / clear-cookie USERID= if logout
Example:
Send redirects for request for articles without a '/'.acl missing_slash path_reg ^/article/[^/]*$ redirect code 301 prefix / drop-query append-slash if missing_slash
Example:
Redirect all HTTP traffic to HTTPS when SSL is handled by haproxy.redirect scheme https if !{ ssl_fc }
See section 7 about ACL usage.
Enable or disable session redistribution in case of connection failure
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
In HTTP mode, if a server designated by a cookie is down, clients may definitely stick to it because they cannot flush the cookie, so they will not be able to access the service anymore. Specifying "redispatch" will allow the proxy to break their persistence and redistribute them to a working server. It also allows to retry last connection to another server in case of multiple connection failures. Of course, it requires having "retries" set to a nonzero value. This form is deprecated, do not use it in any new configuration, use the new "option redispatch" instead.
See also : "option redispatch"
Add a header at the end of the HTTP request
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<string> is the complete line to be added. Any space or known delimiter
must be escaped using a backslash ('\'). Please refer to section
6 about HTTP header manipulation for more information.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
A new line consisting in <string> followed by a line feed will be added after the last header of an HTTP request. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses.
Example :
Add "X-Proto: SSL" to requests coming via port 81acl is-ssl dst_port 81 reqadd X-Proto:\ SSL if is-ssl
Definitely allow an HTTP request if a line matches a regular expression
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The
"reqallow" keyword strictly matches case while "reqiallow"
ignores case.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
A request containing any line which matches extended regular expression <search> will mark the request as allowed, even if any later test would result in a deny. The test applies both to the request line and to request headers. Keep in mind that URLs in request line are case-sensitive while header names are not. It is easier, faster and more powerful to use ACLs to write access policies. Reqdeny, reqallow and reqpass should be avoided in new designs.
Example :
# allow www.* but refuse *.local
reqiallow ^Host:\ www\.
reqideny ^Host:\ .*\.local
Delete all headers matching a regular expression in an HTTP request
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The "reqdel"
keyword strictly matches case while "reqidel" ignores case.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
Any header line matching extended regular expression <search> in the request will be completely deleted. Most common use of this is to remove unwanted and/or dangerous headers or cookies from a request before passing it to the next servers. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Keep in mind that header names are not case-sensitive.
Example :
# remove X-Forwarded-For header and SERVER cookie
reqidel ^X-Forwarded-For:.*
reqidel ^Cookie:.*SERVER=
See also: "reqadd", "reqrep", "rspdel", section 6 about HTTP header manipulation, and section 7 about ACLs.
Deny an HTTP request if a line matches a regular expression
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The
"reqdeny" keyword strictly matches case while "reqideny" ignores
case.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
A request containing any line which matches extended regular expression <search> will mark the request as denied, even if any later test would result in an allow. The test applies both to the request line and to request headers. Keep in mind that URLs in request line are case-sensitive while header names are not. A denied request will generate an "HTTP 403 forbidden" response once the complete request has been parsed. This is consistent with what is practiced using ACLs. It is easier, faster and more powerful to use ACLs to write access policies. Reqdeny, reqallow and reqpass should be avoided in new designs.
Example :
# refuse *.local, then allow www.*
reqideny ^Host:\ .*\.local
reqiallow ^Host:\ www\.
See also: "reqallow", "rspdeny", "block", section 6 about HTTP header manipulation, and section 7 about ACLs.
Ignore any HTTP request line matching a regular expression in next rules
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The
"reqpass" keyword strictly matches case while "reqipass" ignores
case.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
A request containing any line which matches extended regular expression <search> will skip next rules, without assigning any deny or allow verdict. The test applies both to the request line and to request headers. Keep in mind that URLs in request line are case-sensitive while header names are not. It is easier, faster and more powerful to use ACLs to write access policies. Reqdeny, reqallow and reqpass should be avoided in new designs.
Example :
# refuse *.local, then allow www.*, but ignore "www.private.local"
reqipass ^Host:\ www.private\.local
reqideny ^Host:\ .*\.local
reqiallow ^Host:\ www\.
See also: "reqallow", "reqdeny", "block", section 6 about HTTP header manipulation, and section 7 about ACLs.
Replace a regular expression with a string in an HTTP request line
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The "reqrep"
keyword strictly matches case while "reqirep" ignores case.
<string> is the complete line to be added. Any space or known delimiter
must be escaped using a backslash ('\'). References to matched
pattern groups are possible using the common \N form, with N
being a single digit between 0 and 9. Please refer to section
6 about HTTP header manipulation for more information.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
Any line matching extended regular expression <search> in the request (both the request line and header lines) will be completely replaced with <string>. Most common use of this is to rewrite URLs or domain names in "Host" headers. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Note that for increased readability, it is suggested to add enough spaces between the request and the response. Keep in mind that URLs in request line are case-sensitive while header names are not.
Example :
# replace "/static/" with "/" at the beginning of any request path.
reqrep ^([^\ :]*)\ /static/(.*) \1\ /\2
# replace "www.mydomain.com" with "www" in the host name.
reqirep ^Host:\ www.mydomain.com Host:\ www
See also: "reqadd", "reqdel", "rsprep", "tune.bufsize", section 6 about HTTP header manipulation, and section 7 about ACLs.
Tarpit an HTTP request containing a line matching a regular expression
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The
"reqtarpit" keyword strictly matches case while "reqitarpit"
ignores case.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
A request containing any line which matches extended regular expression <search> will be tarpitted, which means that it will connect to nowhere, will be kept open for a pre-defined time, then will return an HTTP error 500 so that the attacker does not suspect it has been tarpitted. The status 500 will be reported in the logs, but the completion flags will indicate "PT". The delay is defined by "timeout tarpit", or "timeout connect" if the former is not set. The goal of the tarpit is to slow down robots attacking servers with identifiable requests. Many robots limit their outgoing number of connections and stay connected waiting for a reply which can take several minutes to come. Depending on the environment and attack, it may be particularly efficient at reducing the load on the network and firewalls.
Examples :
# ignore user-agents reporting any flavour of "Mozilla" or "MSIE", but
# block all others.
reqipass ^User-Agent:\.*(Mozilla|MSIE)
reqitarpit ^User-Agent:
# block bad guys
acl badguys src 10.1.0.3 172.16.13.20/28
reqitarpit . if badguys
See also: "reqallow", "reqdeny", "reqpass", section 6 about HTTP header manipulation, and section 7 about ACLs.
Set the number of retries to perform on a server after a connection failure
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<value> is the number of times a connection attempt should be retried on
a server when a connection either is refused or times out. The
default value is 3.
It is important to understand that this value applies to the number of connection attempts, not full requests. When a connection has effectively been established to a server, there will be no more retry. In order to avoid immediate reconnections to a server which is restarting, a turn-around timer of 1 second is applied before a retry occurs. When "option redispatch" is set, the last retry may be performed on another server even if a cookie references a different server.
See also : "option redispatch"
Add a header at the end of the HTTP response
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<string> is the complete line to be added. Any space or known delimiter
must be escaped using a backslash ('\'). Please refer to section
6 about HTTP header manipulation for more information.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
A new line consisting in <string> followed by a line feed will be added after the last header of an HTTP response. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses.
Delete all headers matching a regular expression in an HTTP response
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
response line. This is an extended regular expression, so
parenthesis grouping is supported and no preliminary backslash
is required. Any space or known delimiter must be escaped using
a backslash ('\'). The pattern applies to a full line at a time.
The "rspdel" keyword strictly matches case while "rspidel"
ignores case.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
Any header line matching extended regular expression <search> in the response will be completely deleted. Most common use of this is to remove unwanted and/or sensitive headers or cookies from a response before passing it to the client. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Keep in mind that header names are not case-sensitive.
Example :
# remove the Server header from responses
rspidel ^Server:.*
See also: "rspadd", "rsprep", "reqdel", section 6 about HTTP header manipulation, and section 7 about ACLs.
Block an HTTP response if a line matches a regular expression
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
response line. This is an extended regular expression, so
parenthesis grouping is supported and no preliminary backslash
is required. Any space or known delimiter must be escaped using
a backslash ('\'). The pattern applies to a full line at a time.
The "rspdeny" keyword strictly matches case while "rspideny"
ignores case.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
A response containing any line which matches extended regular expression <search> will mark the request as denied. The test applies both to the response line and to response headers. Keep in mind that header names are not case-sensitive. Main use of this keyword is to prevent sensitive information leak and to block the response before it reaches the client. If a response is denied, it will be replaced with an HTTP 502 error so that the client never retrieves any sensitive data. It is easier, faster and more powerful to use ACLs to write access policies. Rspdeny should be avoided in new designs.
Example :
# Ensure that no content type matching ms-word will leak
rspideny ^Content-type:\.*/ms-word
See also: "reqdeny", "acl", "block", section 6 about HTTP header manipulation and section 7 about ACLs.
Replace a regular expression with a string in an HTTP response line
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<search> is the regular expression applied to HTTP headers and to the
response line. This is an extended regular expression, so
parenthesis grouping is supported and no preliminary backslash
is required. Any space or known delimiter must be escaped using
a backslash ('\'). The pattern applies to a full line at a time.
The "rsprep" keyword strictly matches case while "rspirep"
ignores case.
<string> is the complete line to be added. Any space or known delimiter
must be escaped using a backslash ('\'). References to matched
pattern groups are possible using the common \N form, with N
being a single digit between 0 and 9. Please refer to section
6 about HTTP header manipulation for more information.
<cond> is an optional matching condition built from ACLs. It makes it
possible to ignore this rule when other conditions are not met.
Any line matching extended regular expression <search> in the response (both the response line and header lines) will be completely replaced with <string>. Most common use of this is to rewrite Location headers. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Note that for increased readability, it is suggested to add enough spaces between the request and the response. Keep in mind that header names are not case-sensitive.
Example :
# replace "Location: 127.0.0.1:8080" with "Location: www.mydomain.com"
rspirep ^Location:\ 127.0.0.1:8080 Location:\ www.mydomain.com
See also: "rspadd", "rspdel", "reqrep", section 6 about HTTP header manipulation, and section 7 about ACLs.
Declare a server in a backend
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<name> is the internal name assigned to this server. This name will
appear in logs and alerts. If "http-send-name-header" is
set, it will be added to the request header sent to the server.
<address> is the IPv4 or IPv6 address of the server. Alternatively, a
resolvable hostname is supported, but this name will be resolved
during start-up. Address "0.0.0.0" or "*" has a special meaning.
It indicates that the connection will be forwarded to the same IP
address as the one from the client connection. This is useful in
transparent proxy architectures where the client's connection is
intercepted and haproxy must forward to the original destination
address. This is more or less what the "transparent" keyword does
except that with a server it's possible to limit concurrency and
to report statistics. Optionally, an address family prefix may be
used before the address to force the family regardless of the
address format, which can be useful to specify a path to a unix
socket with no slash ('/'). Currently supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'unix@' -> address is a path to a local unix socket
Any part of the address string may reference any number of
environment variables by preceding their name with a dollar
sign ('$') and optionally enclosing them with braces ('{}'),
similarly to what is done in Bourne shell.
<port> is an optional port specification. If set, all connections will
be sent to this port. If unset, the same port the client
connected to will be used. The port may also be prefixed by a "+"
or a "-". In this case, the server's port will be determined by
adding this value to the client's port.
<param*> is a list of parameters for this server. The "server" keywords
accepts an important number of options and has a complete section
dedicated to it. Please refer to section 5 for more details.
Examples :
server first 10.1.1.1:1080 cookie first check inter 1000
server second 10.1.1.2:1080 cookie second check inter 1000
server transp ipv4@
server backup ${SRV_BACKUP}:1080 backup
server www1_dc1 ${LAN_DC1}.101:80
server www1_dc2 ${LAN_DC2}.101:80
Set the source address for outgoing connections
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<addr> is the IPv4 address HAProxy will bind to before connecting to a
server. This address is also used as a source for health checks.
The default value of 0.0.0.0 means that the system will select
the most appropriate address to reach its destination. Optionally
an address family prefix may be used before the address to force
the family regardless of the address format, which can be useful
to specify a path to a unix socket with no slash ('/'). Currently
supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'unix@' -> address is a path to a local unix socket
Any part of the address string may reference any number of
environment variables by preceding their name with a dollar
sign ('$') and optionally enclosing them with braces ('{}'),
similarly to what is done in Bourne shell.
<port> is an optional port. It is normally not needed but may be useful
in some very specific contexts. The default value of zero means
the system will select a free port. Note that port ranges are not
supported in the backend. If you want to force port ranges, you
have to specify them on each "server" line.
<addr2> is the IP address to present to the server when connections are
forwarded in full transparent proxy mode. This is currently only
supported on some patched Linux kernels. When this address is
specified, clients connecting to the server will be presented
with this address, while health checks will still use the address
<addr>.
<port2> is the optional port to present to the server when connections
are forwarded in full transparent proxy mode (see <addr2> above).
The default value of zero means the system will select a free
port.
<hdr> is the name of a HTTP header in which to fetch the IP to bind to.
This is the name of a comma-separated header list which can
contain multiple IP addresses. By default, the last occurrence is
used. This is designed to work with the X-Forwarded-For header
and to automatically bind to the client's IP address as seen
by previous proxy, typically Stunnel. In order to use another
occurrence from the last one, please see the <occ> parameter
below. When the header (or occurrence) is not found, no binding
is performed so that the proxy's default IP address is used. Also
keep in mind that the header name is case insensitive, as for any
HTTP header.
<occ> is the occurrence number of a value to be used in a multi-value
header. This is to be used in conjunction with "hdr_ip(<hdr>)",
in order to specify which occurrence to use for the source IP
address. Positive values indicate a position from the first
occurrence, 1 being the first one. Negative values indicate
positions relative to the last one, -1 being the last one. This
is helpful for situations where an X-Forwarded-For header is set
at the entry point of an infrastructure and must be used several
proxy layers away. When this value is not specified, -1 is
assumed. Passing a zero here disables the feature.
<name> is an optional interface name to which to bind to for outgoing
traffic. On systems supporting this features (currently, only
Linux), this allows one to bind all traffic to the server to
this interface even if it is not the one the system would select
based on routing tables. This should be used with extreme care.
Note that using this option requires root privileges.
The "source" keyword is useful in complex environments where a specific address only is allowed to connect to the servers. It may be needed when a private address must be used through a public gateway for instance, and it is known that the system cannot determine the adequate source address by itself. An extension which is available on certain patched Linux kernels may be used through the "usesrc" optional keyword. It makes it possible to connect to the servers with an IP address which does not belong to the system itself. This is called "full transparent proxy mode". For this to work, the destination servers have to route their traffic back to this address through the machine running HAProxy, and IP forwarding must generally be enabled on this machine. In this "full transparent proxy" mode, it is possible to force a specific IP address to be presented to the servers. This is not much used in fact. A more common use is to tell HAProxy to present the client's IP address. For this, there are two methods : - present the client's IP and port addresses. This is the most transparent mode, but it can cause problems when IP connection tracking is enabled on the machine, because a same connection may be seen twice with different states. However, this solution presents the huge advantage of not limiting the system to the 64k outgoing address+port couples, because all of the client ranges may be used. - present only the client's IP address and select a spare port. This solution is still quite elegant but slightly less transparent (downstream firewalls logs will not match upstream's). It also presents the downside of limiting the number of concurrent connections to the usual 64k ports. However, since the upstream and downstream ports are different, local IP connection tracking on the machine will not be upset by the reuse of the same session. Note that depending on the transparent proxy technology used, it may be required to force the source address. In fact, cttproxy version 2 requires an IP address in <addr> above, and does not support setting of "0.0.0.0" as the IP address because it creates NAT entries which much match the exact outgoing address. Tproxy version 4 and some other kernel patches which work in pure forwarding mode generally will not have this limitation. This option sets the default source for all servers in the backend. It may also be specified in a "defaults" section. Finer source address specification is possible at the server level using the "source" server option. Refer to section 5 for more information.
Examples :
backend private
# Connect to the servers using our 192.168.1.200 source address
source 192.168.1.200
backend transparent_ssl1
# Connect to the SSL farm from the client's source address
source 192.168.1.200 usesrc clientip
backend transparent_ssl2
# Connect to the SSL farm from the client's source address and port
# not recommended if IP conntrack is present on the local machine.
source 192.168.1.200 usesrc client
backend transparent_ssl3
# Connect to the SSL farm from the client's source address. It
# is more conntrack-friendly.
source 192.168.1.200 usesrc clientip
backend transparent_smtp
# Connect to the SMTP farm from the client's source address/port
# with Tproxy version 4.
source 0.0.0.0 usesrc clientip
backend transparent_http
# Connect to the servers using the client's IP as seen by previous
# proxy.
source 0.0.0.0 usesrc hdr_ip(x-forwarded-for,-1)
See also : the "source" server option in section 5, the Tproxy patches for the Linux kernel on www.balabit.com, the "bind" keyword.
Set the maximum inactivity time on the server side.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The inactivity timeout applies when the server is expected to acknowledge or send data. In HTTP mode, this timeout is particularly important to consider during the first phase of the server's response, when it has to send the headers, as it directly represents the server's processing time for the request. To find out what value to put there, it's often good to start with what would be considered as unacceptable response times, then check the logs to observe the response time distribution, and adjust the value accordingly. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly recommended that the client timeout remains equal to the server timeout in order to avoid complex situations to debug. Whatever the expected server response times, it is a good practice to cover at least one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds minimum). This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of expired sessions in the system if the system's timeouts are not configured either. This parameter is provided for compatibility but is currently deprecated. Please use "timeout server" instead.
Enable statistics admin level if/unless a condition is matched
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
This statement enables the statistics admin level if/unless a condition is
matched.
The admin level allows to enable/disable servers from the web interface. By
default, statistics page is read-only for security reasons.
Note : Consider not using this feature in multi-process mode (nbproc > 1)
unless you know what you do : memory is not shared between the
processes, which can result in random behaviours.
Currently, the POST request is limited to the buffer size minus the reserved
buffer space, which means that if the list of servers is too long, the
request won't be processed. It is recommended to alter few servers at a
time.
Example :
# statistics admin level only for localhost
backend stats_localhost
stats enable
stats admin if LOCALHOST
Example :
# statistics admin level always enabled because of the authentication
backend stats_auth
stats enable
stats auth admin:AdMiN123
stats admin if TRUE
Example :
# statistics admin level depends on the authenticated user
userlist stats-auth
group admin users admin
user admin insecure-password AdMiN123
group readonly users haproxy
user haproxy insecure-password haproxy
backend stats_auth
stats enable
acl AUTH http_auth(stats-auth)
acl AUTH_ADMIN http_auth_group(stats-auth) admin
stats http-request auth unless AUTH
stats admin if AUTH_ADMIN
See also : "stats enable", "stats auth", "stats http-request", "nbproc", "bind-process", section 3.4 about userlists and section 7 about ACL usage.
Enable statistics with authentication and grant access to an account
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<user> is a user name to grant access to <passwd> is the cleartext password associated to this user
This statement enables statistics with default settings, and restricts access to declared users only. It may be repeated as many times as necessary to allow as many users as desired. When a user tries to access the statistics without a valid account, a "401 Forbidden" response will be returned so that the browser asks the user to provide a valid user and password. The real which will be returned to the browser is configurable using "stats realm". Since the authentication method is HTTP Basic Authentication, the passwords circulate in cleartext on the network. Thus, it was decided that the configuration file would also use cleartext passwords to remind the users that those ones should not be sensitive and not shared with any other account. It is also possible to reduce the scope of the proxies which appear in the report using "stats scope". Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters.
Example :
# public access (limited to this backend only)
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm Haproxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable statistics reporting with default settings
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
This statement enables statistics reporting with default settings defined at build time. Unless stated otherwise, these settings are used : - stats uri : /haproxy?stats - stats realm : "HAProxy Statistics" - stats auth : no authentication - stats scope : no restriction Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters.
Example :
# public access (limited to this backend only)
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm Haproxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable statistics and hide HAProxy version reporting
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
By default, the stats page reports some useful status information along with the statistics. Among them is HAProxy's version. However, it is generally considered dangerous to report precise version to anyone, as it can help them target known weaknesses with specific attacks. The "stats hide-version" statement removes the version from the statistics report. This is recommended for public sites or any site with a weak login/password. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters.
Example :
# public access (limited to this backend only)
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm Haproxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Access control for statistics
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
As "http-request", these set of options allow to fine control access to statistics. Each option may be followed by if/unless and acl. First option with matched condition (or option without condition) is final. For "deny" a 403 error will be returned, for "allow" normal processing is performed, for "auth" a 401/407 error code is returned so the client should be asked to enter a username and password. There is no fixed limit to the number of http-request statements per instance.
Enable statistics and set authentication realm
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<realm> is the name of the HTTP Basic Authentication realm reported to
the browser. The browser uses it to display it in the pop-up
inviting the user to enter a valid username and password.
The realm is read as a single word, so any spaces in it should be escaped
using a backslash ('\').
This statement is useful only in conjunction with "stats auth" since it is
only related to authentication.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
# public access (limited to this backend only)
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm Haproxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable statistics with automatic refresh
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<delay> is the suggested refresh delay, specified in seconds, which will
be returned to the browser consulting the report page. While the
browser is free to apply any delay, it will generally respect it
and refresh the page this every seconds. The refresh interval may
be specified in any other non-default time unit, by suffixing the
unit after the value, as explained at the top of this document.
This statement is useful on monitoring displays with a permanent page reporting the load balancer's activity. When set, the HTML report page will include a link "refresh"/"stop refresh" so that the user can select whether he wants automatic refresh of the page or not. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters.
Example :
# public access (limited to this backend only)
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm Haproxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable statistics and limit access scope
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<name> is the name of a listen, frontend or backend section to be
reported. The special name "." (a single dot) designates the
section in which the statement appears.
When this statement is specified, only the sections enumerated with this statement will appear in the report. All other ones will be hidden. This statement may appear as many times as needed if multiple sections need to be reported. Please note that the name checking is performed as simple string comparisons, and that it is never checked that a give section name really exists. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters.
Example :
# public access (limited to this backend only)
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm Haproxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable reporting of a description on the statistics page.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
<desc> is an optional description to be reported. If unspecified, the
description from global section is automatically used instead.
This statement is useful for users that offer shared services to their
customers, where node or description should be different for each customer.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters. By default description is not shown.
Example :
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats show-desc Master node for Europe, Asia, Africa
stats uri /admin?stats
stats refresh 5s
Enable reporting additional informations on the statistics page : - cap: capabilities (proxy) - mode: one of tcp, http or health (proxy) - id: SNMP ID (proxy, socket, server) - IP (socket, server) - cookie (backend, server) Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Default behaviour is not to show this information.
See also: "stats enable", "stats uri".
Enable reporting of a host name on the statistics page.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments:
<name> is an optional name to be reported. If unspecified, the
node name from global section is automatically used instead.
This statement is useful for users that offer shared services to their customers, where node or description might be different on a stats page provided for each customer. Default behaviour is not to show host name. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters.
Example:
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats show-node Europe-1
stats uri /admin?stats
stats refresh 5s
Enable statistics and define the URI prefix to access them
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<prefix> is the prefix of any URI which will be redirected to stats. This
prefix may contain a question mark ('?') to indicate part of a
query string.
The statistics URI is intercepted on the relayed traffic, so it appears as a page within the normal application. It is strongly advised to ensure that the selected URI will never appear in the application, otherwise it will never be possible to reach it in the application. The default URI compiled in haproxy is "/haproxy?stats", but this may be changed at build time, so it's better to always explicitly specify it here. It is generally a good idea to include a question mark in the URI so that intermediate proxies refrain from caching the results. Also, since any string beginning with the prefix will be accepted as a stats request, the question mark helps ensuring that no valid URI will begin with the same words. It is sometimes very convenient to use "/" as the URI prefix, and put that statement in a "listen" instance of its own. That makes it easy to dedicate an address or a port to statistics only. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters.
Example :
# public access (limited to this backend only)
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm Haproxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Define a request pattern matching condition to stick a user to a server
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<pattern> is a pattern extraction rule as described in section 7.8. It describes what elements of the incoming request or connection will be analysed in the hope to find a matching entry in a stickiness table. This rule is mandatory. <table> is an optional stickiness table name. If unspecified, the same backend's table is used. A stickiness table is declared using the "stick-table" statement. <cond> is an optional matching condition. It makes it possible to match on a certain criterion only when other conditions are met (or not met). For instance, it could be used to match on a source IP address except when a request passes through a known proxy, in which case we'd match on a header containing that IP address.
Some protocols or applications require complex stickiness rules and cannot always simply rely on cookies nor hashing. The "stick match" statement describes a rule to extract the stickiness criterion from an incoming request or connection. See section 7 for a complete list of possible patterns and transformation rules. The table has to be declared using the "stick-table" statement. It must be of a type compatible with the pattern. By default it is the one which is present in the same backend. It is possible to share a table with other backends by referencing it using the "table" keyword. If another table is referenced, the server's ID inside the backends are used. By default, all server IDs start at 1 in each backend, so the server ordering is enough. But in case of doubt, it is highly recommended to force server IDs using their "id" setting. It is possible to restrict the conditions where a "stick match" statement will apply, using "if" or "unless" followed by a condition. See section 7 for ACL based conditions. There is no limit on the number of "stick match" statements. The first that applies and matches will cause the request to be directed to the same server as was used for the request which created the entry. That way, multiple matches can be used as fallbacks. The stick rules are checked after the persistence cookies, so they will not affect stickiness if a cookie has already been used to select a server. That way, it becomes very easy to insert cookies and match on IP addresses in order to maintain stickiness between HTTP and HTTPS. Note : Consider not using this feature in multi-process mode (nbproc > 1) unless you know what you do : memory is not shared between the processes, which can result in random behaviours.
Example :
# forward SMTP users to the same server they just used for POP in the
# last 30 minutes
backend pop
mode tcp
balance roundrobin
stick store-request src
stick-table type ip size 200k expire 30m
server s1 192.168.1.1:110
server s2 192.168.1.1:110
backend smtp
mode tcp
balance roundrobin
stick match src table pop
server s1 192.168.1.1:25
server s2 192.168.1.1:25
See also : "stick-table", "stick on", "nbproc", "bind-process" and section 7 about ACLs and pattern extraction.
Define a request pattern to associate a user to a server
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Note : This form is exactly equivalent to "stick match" followed by "stick store-request", all with the same arguments. Please refer to both keywords for details. It is only provided as a convenience for writing more maintainable configurations. Note : Consider not using this feature in multi-process mode (nbproc > 1) unless you know what you do : memory is not shared between the processes, which can result in random behaviours.
Examples :
# The following form ...
stick on src table pop if !localhost
# ...is strictly equivalent to this one :
stick match src table pop if !localhost
stick store-request src table pop if !localhost
# Use cookie persistence for HTTP, and stick on source address for HTTPS as
# well as HTTP without cookie. Share the same table between both accesses.
backend http
mode http
balance roundrobin
stick on src table https
cookie SRV insert indirect nocache
server s1 192.168.1.1:80 cookie s1
server s2 192.168.1.1:80 cookie s2
backend https
mode tcp
balance roundrobin
stick-table type ip size 200k expire 30m
stick on src
server s1 192.168.1.1:443
server s2 192.168.1.1:443
Define a request pattern used to create an entry in a stickiness table
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<pattern> is a pattern extraction rule as described in section 7.8. It describes what elements of the incoming request or connection will be analysed, extracted and stored in the table once a server is selected. <table> is an optional stickiness table name. If unspecified, the same backend's table is used. A stickiness table is declared using the "stick-table" statement. <cond> is an optional storage condition. It makes it possible to store certain criteria only when some conditions are met (or not met). For instance, it could be used to store the source IP address except when the request passes through a known proxy, in which case we'd store a converted form of a header containing that IP address.
Some protocols or applications require complex stickiness rules and cannot always simply rely on cookies nor hashing. The "stick store-request" statement describes a rule to decide what to extract from the request and when to do it, in order to store it into a stickiness table for further requests to match it using the "stick match" statement. Obviously the extracted part must make sense and have a chance to be matched in a further request. Storing a client's IP address for instance often makes sense. Storing an ID found in a URL parameter also makes sense. Storing a source port will almost never make any sense because it will be randomly matched. See section 7 for a complete list of possible patterns and transformation rules. The table has to be declared using the "stick-table" statement. It must be of a type compatible with the pattern. By default it is the one which is present in the same backend. It is possible to share a table with other backends by referencing it using the "table" keyword. If another table is referenced, the server's ID inside the backends are used. By default, all server IDs start at 1 in each backend, so the server ordering is enough. But in case of doubt, it is highly recommended to force server IDs using their "id" setting. It is possible to restrict the conditions where a "stick store-request" statement will apply, using "if" or "unless" followed by a condition. This condition will be evaluated while parsing the request, so any criteria can be used. See section 7 for ACL based conditions. There is no limit on the number of "stick store-request" statements, but there is a limit of 8 simultaneous stores per request or response. This makes it possible to store up to 8 criteria, all extracted from either the request or the response, regardless of the number of rules. Only the 8 first ones which match will be kept. Using this, it is possible to feed multiple tables at once in the hope to increase the chance to recognize a user on another protocol or access method. The "store-request" rules are evaluated once the server connection has been established, so that the table will contain the real server that processed the request. Note : Consider not using this feature in multi-process mode (nbproc > 1) unless you know what you do : memory is not shared between the processes, which can result in random behaviours.
Example :
# forward SMTP users to the same server they just used for POP in the
# last 30 minutes
backend pop
mode tcp
balance roundrobin
stick store-request src
stick-table type ip size 200k expire 30m
server s1 192.168.1.1:110
server s2 192.168.1.1:110
backend smtp
mode tcp
balance roundrobin
stick match src table pop
server s1 192.168.1.1:25
server s2 192.168.1.1:25
See also : "stick-table", "stick on", "nbproc", "bind-process" and section 7 about ACLs and pattern extraction.
stick-table type {ip | integer | string [len <length>] | binary [len <length>]}
size <size> [expire <expire>] [nopurge] [peers <peersect>]
[store <data_type>]*
Configure the stickiness table for the current backend
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
ip a table declared with "type ip" will only store IPv4 addresses.
This form is very compact (about 50 bytes per entry) and allows
very fast entry lookup and stores with almost no overhead. This
is mainly used to store client source IP addresses.
ipv6 a table declared with "type ipv6" will only store IPv6 addresses.
This form is very compact (about 60 bytes per entry) and allows
very fast entry lookup and stores with almost no overhead. This
is mainly used to store client source IP addresses.
integer a table declared with "type integer" will store 32bit integers
which can represent a client identifier found in a request for
instance.
string a table declared with "type string" will store substrings of up
to <len> characters. If the string provided by the pattern
extractor is larger than <len>, it will be truncated before
being stored. During matching, at most <len> characters will be
compared between the string in the table and the extracted
pattern. When not specified, the string is automatically limited
to 32 characters.
binary a table declared with "type binary" will store binary blocks
of <len> bytes. If the block provided by the pattern
extractor is larger than <len>, it will be truncated before
being stored. If the block provided by the pattern extractor
is shorter than <len>, it will be padded by 0. When not
specified, the block is automatically limited to 32 bytes.
<length> is the maximum number of characters that will be stored in a
"string" type table (See type "string" above). Or the number
of bytes of the block in "binary" type table. Be careful when
changing this parameter as memory usage will proportionally
increase.
<size> is the maximum number of entries that can fit in the table. This
value directly impacts memory usage. Count approximately
50 bytes per entry, plus the size of a string if any. The size
supports suffixes "k", "m", "g" for 2^10, 2^20 and 2^30 factors.
[nopurge] indicates that we refuse to purge older entries when the table
is full. When not specified and the table is full when haproxy
wants to store an entry in it, it will flush a few of the oldest
entries in order to release some space for the new ones. This is
most often the desired behaviour. In some specific cases, it
be desirable to refuse new entries instead of purging the older
ones. That may be the case when the amount of data to store is
far above the hardware limits and we prefer not to offer access
to new clients than to reject the ones already connected. When
using this parameter, be sure to properly set the "expire"
parameter (see below).
<peersect> is the name of the peers section to use for replication. Entries
which associate keys to server IDs are kept synchronized with
the remote peers declared in this section. All entries are also
automatically learned from the local peer (old process) during a
soft restart.
NOTE : peers can't be used in multi-process mode.
<expire> defines the maximum duration of an entry in the table since it
was last created, refreshed or matched. The expiration delay is
defined using the standard time format, similarly as the various
timeouts. The maximum duration is slightly above 24 days. See
section 2.2 for more information. If this delay is not specified,
the session won't automatically expire, but older entries will
be removed once full. Be sure not to use the "nopurge" parameter
if not expiration delay is specified.
<data_type> is used to store additional information in the stick-table. This
may be used by ACLs in order to control various criteria related
to the activity of the client matching the stick-table. For each
item specified here, the size of each entry will be inflated so
that the additional data can fit. Several data types may be
stored with an entry. Multiple data types may be specified after
the "store" keyword, as a comma-separated list. Alternatively,
it is possible to repeat the "store" keyword followed by one or
several data types. Except for the "server_id" type which is
automatically detected and enabled, all data types must be
explicitly declared to be stored. If an ACL references a data
type which is not stored, the ACL will simply not match. Some
data types require an argument which must be passed just after
the type between parenthesis. See below for the supported data
types and their arguments.
The data types that can be stored with an entry are the following :
- server_id : this is an integer which holds the numeric ID of the server a
request was assigned to. It is used by the "stick match", "stick store",
and "stick on" rules. It is automatically enabled when referenced.
- gpc0 : first General Purpose Counter. It is a positive 32-bit integer
integer which may be used for anything. Most of the time it will be used
to put a special tag on some entries, for instance to note that a
specific behaviour was detected and must be known for future matches.
- conn_cnt : Connection Count. It is a positive 32-bit integer which counts
the absolute number of connections received from clients which matched
this entry. It does not mean the connections were accepted, just that
they were received.
- conn_cur : Current Connections. It is a positive 32-bit integer which
stores the concurrent connection counts for the entry. It is incremented
once an incoming connection matches the entry, and decremented once the
connection leaves. That way it is possible to know at any time the exact
number of concurrent connections for an entry.
- conn_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
incoming connection rate over that period, in connections per period. The
result is an integer which can be matched using ACLs.
- sess_cnt : Session Count. It is a positive 32-bit integer which counts
the absolute number of sessions received from clients which matched this
entry. A session is a connection that was accepted by the layer 4 rules.
- sess_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
incoming session rate over that period, in sessions per period. The
result is an integer which can be matched using ACLs.
- http_req_cnt : HTTP request Count. It is a positive 32-bit integer which
counts the absolute number of HTTP requests received from clients which
matched this entry. It does not matter whether they are valid requests or
not. Note that this is different from sessions when keep-alive is used on
the client side.
- http_req_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
HTTP request rate over that period, in requests per period. The result is
an integer which can be matched using ACLs. It does not matter whether
they are valid requests or not. Note that this is different from sessions
when keep-alive is used on the client side.
- http_err_cnt : HTTP Error Count. It is a positive 32-bit integer which
counts the absolute number of HTTP requests errors induced by clients
which matched this entry. Errors are counted on invalid and truncated
requests, as well as on denied or tarpitted requests, and on failed
authentications. If the server responds with 4xx, then the request is
also counted as an error since it's an error triggered by the client
(eg: vulnerability scan).
- http_err_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
HTTP request error rate over that period, in requests per period (see
http_err_cnt above for what is accounted as an error). The result is an
integer which can be matched using ACLs.
- bytes_in_cnt : client to server byte count. It is a positive 64-bit
integer which counts the cumulated amount of bytes received from clients
which matched this entry. Headers are included in the count. This may be
used to limit abuse of upload features on photo or video servers.
- bytes_in_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
incoming bytes rate over that period, in bytes per period. It may be used
to detect users which upload too much and too fast. Warning: with large
uploads, it is possible that the amount of uploaded data will be counted
once upon termination, thus causing spikes in the average transfer speed
instead of having a smooth one. This may partially be smoothed with
"option contstats" though this is not perfect yet. Use of byte_in_cnt is
recommended for better fairness.
- bytes_out_cnt : server to client byte count. It is a positive 64-bit
integer which counts the cumulated amount of bytes sent to clients which
matched this entry. Headers are included in the count. This may be used
to limit abuse of bots sucking the whole site.
- bytes_out_rate(<period>) : frequency counter (takes 12 bytes). It takes
an integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
outgoing bytes rate over that period, in bytes per period. It may be used
to detect users which download too much and too fast. Warning: with large
transfers, it is possible that the amount of transferred data will be
counted once upon termination, thus causing spikes in the average
transfer speed instead of having a smooth one. This may partially be
smoothed with "option contstats" though this is not perfect yet. Use of
byte_out_cnt is recommended for better fairness.
There is only one stick-table per proxy. At the moment of writing this doc,
it does not seem useful to have multiple tables per proxy. If this happens
to be required, simply create a dummy backend with a stick-table in it and
reference it.
It is important to understand that stickiness based on learning information
has some limitations, including the fact that all learned associations are
lost upon restart. In general it can be good as a complement but not always
as an exclusive stickiness.
Last, memory requirements may be important when storing many data types.
Indeed, storing all indicators above at once in each entry requires 116 bytes
per entry, or 116 MB for a 1-million entries table. This is definitely not
something that can be ignored.
Example:
# Keep track of counters of up to 1 million IP addresses over 5 minutes
# and store a general purpose counter and the average connection rate
# computed over a sliding window of 30 seconds.
stick-table type ip size 1m expire 5m store gpc0,conn_rate(30s)
See also : "stick match", "stick on", "stick store-request", section 2.2 about time format and section 7 about ACLs.
Define a request pattern used to create an entry in a stickiness table
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<pattern> is a pattern extraction rule as described in section 7.8. It describes what elements of the response or connection will be analysed, extracted and stored in the table once a server is selected. <table> is an optional stickiness table name. If unspecified, the same backend's table is used. A stickiness table is declared using the "stick-table" statement. <cond> is an optional storage condition. It makes it possible to store certain criteria only when some conditions are met (or not met). For instance, it could be used to store the SSL session ID only when the response is a SSL server hello.
Some protocols or applications require complex stickiness rules and cannot always simply rely on cookies nor hashing. The "stick store-response" statement describes a rule to decide what to extract from the response and when to do it, in order to store it into a stickiness table for further requests to match it using the "stick match" statement. Obviously the extracted part must make sense and have a chance to be matched in a further request. Storing an ID found in a header of a response makes sense. See section 7 for a complete list of possible patterns and transformation rules. The table has to be declared using the "stick-table" statement. It must be of a type compatible with the pattern. By default it is the one which is present in the same backend. It is possible to share a table with other backends by referencing it using the "table" keyword. If another table is referenced, the server's ID inside the backends are used. By default, all server IDs start at 1 in each backend, so the server ordering is enough. But in case of doubt, it is highly recommended to force server IDs using their "id" setting. It is possible to restrict the conditions where a "stick store-response" statement will apply, using "if" or "unless" followed by a condition. This condition will be evaluated while parsing the response, so any criteria can be used. See section 7 for ACL based conditions. There is no limit on the number of "stick store-response" statements, but there is a limit of 8 simultaneous stores per request or response. This makes it possible to store up to 8 criteria, all extracted from either the request or the response, regardless of the number of rules. Only the 8 first ones which match will be kept. Using this, it is possible to feed multiple tables at once in the hope to increase the chance to recognize a user on another protocol or access method. The table will contain the real server that processed the request.
Example :
# Learn SSL session ID from both request and response and create affinity.
backend https
mode tcp
balance roundrobin
# maximum SSL session ID length is 32 bytes.
stick-table type binary len 32 size 30k expire 30m
acl clienthello req_ssl_hello_type 1
acl serverhello rep_ssl_hello_type 2
# use tcp content accepts to detects ssl client and server hello.
tcp-request inspect-delay 5s
tcp-request content accept if clienthello
# no timeout on response inspect delay by default.
tcp-response content accept if serverhello
# SSL session ID (SSLID) may be present on a client or server hello.
# Its length is coded on 1 byte at offset 43 and its value starts
# at offset 44.
# Match and learn on request if client hello.
stick on payload_lv(43,1) if clienthello
# Learn on response if server hello.
stick store-response payload_lv(43,1) if serverhello
server s1 192.168.1.1:443
server s2 192.168.1.1:443
Perform an action on an incoming connection depending on a layer 4 condition
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | no |
Arguments :
<action> defines the action to perform if the condition applies. Valid
actions include : "accept", "reject", "track-sc1", "track-sc2".
See below for more details.
<condition> is a standard layer4-only ACL-based condition (see section 7).
Immediately after acceptance of a new incoming connection, it is possible to evaluate some conditions to decide whether this connection must be accepted or dropped or have its counters tracked. Those conditions cannot make use of any data contents because the connection has not been read from yet, and the buffers are not yet allocated. This is used to selectively and very quickly accept or drop connections from various sources with a very low overhead. If some contents need to be inspected in order to take the decision, the "tcp-request content" statements must be used instead. The "tcp-request connection" rules are evaluated in their exact declaration order. If no rule matches or if there is no rule, the default action is to accept the incoming connection. There is no specific limit to the number of rules which may be inserted. Three types of actions are supported : - accept : accepts the connection if the condition is true (when used with "if") or false (when used with "unless"). The first such rule executed ends the rules evaluation. - reject : rejects the connection if the condition is true (when used with "if") or false (when used with "unless"). The first such rule executed ends the rules evaluation. Rejected connections do not even become a session, which is why they are accounted separately for in the stats, as "denied connections". They are not considered for the session rate-limit and are not logged either. The reason is that these rules should only be used to filter extremely high connection rates such as the ones encountered during a massive DDoS attack. Under these extreme conditions, the simple action of logging each event would make the system collapse and would considerably lower the filtering capacity. If logging is absolutely desired, then "tcp-request content" rules should be used instead. - { track-sc1 | track-sc2 } <key> [table <table>] : enables tracking of sticky counters from current connection. These rules do not stop evaluation and do not change default action. Two sets of counters may be simultaneously tracked by the same connection. The first "track-sc1" rule executed enables tracking of the counters of the specified table as the first set. The first "track-sc2" rule executed enables tracking of the counters of the specified table as the second set. It is a recommended practice to use the first set of counters for the per-frontend counters and the second set for the per-backend ones. These actions take one or two arguments : <key> is mandatory, and is a pattern extraction rule as described in section 7.8. It describes what elements of the incoming request or connection will be analysed, extracted, combined, and used to select which table entry to update the counters. Note that "tcp-request connection" cannot use content-based fetches. <table> is an optional table to be used instead of the default one, which is the stick-table declared in the current proxy. All the counters for the matches and updates for the key will then be performed in that table until the session ends. Once a "track-sc*" rule is executed, the key is looked up in the table and if it is not found, an entry is allocated for it. Then a pointer to that entry is kept during all the session's life, and this entry's counters are updated as often as possible, every time the session's counters are updated, and also systematically when the session ends. Counters are only updated for events that happen after the tracking has been started. For example, connection counters will not be updated when tracking layer 7 information, since the connection event happens before layer7 information is extracted. If the entry tracks concurrent connection counters, one connection is counted for as long as the entry is tracked, and the entry will not expire during that time. Tracking counters also provides a performance advantage over just checking the keys, because only one table lookup is performed for all ACL checks that make use of it. Note that the "if/unless" condition is optional. If no condition is set on the action, it is simply performed unconditionally. That can be useful for "track-sc*" actions as well as for changing the default action to a reject.
Example:
Accept all connections from white-listed hosts, reject too fast connection without counting them, and track accepted connections. This results in connection rate being capped from abusive sources.tcp-request connection accept if { src -f /etc/haproxy/whitelist.lst } tcp-request connection reject if { src_conn_rate gt 10 } tcp-request connection track-sc1 src
Example:
Accept all connections from white-listed hosts, count all other connections and reject too fast ones. This results in abusive ones being blocked as long as they don't slow down.tcp-request connection accept if { src -f /etc/haproxy/whitelist.lst } tcp-request connection track-sc1 src tcp-request connection reject if { sc1_conn_rate gt 10 }
See section 7 about ACL usage.
See also : "tcp-request content", "stick-table"
Perform an action on a new session depending on a layer 4-7 condition
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<action> defines the action to perform if the condition applies. Valid
actions include : "accept", "reject", "track-sc1", "track-sc2".
See "tcp-request connection" above for their signification.
<condition> is a standard layer 4-7 ACL-based condition (see section 7).
A request's contents can be analysed at an early stage of request processing called "TCP content inspection". During this stage, ACL-based rules are evaluated every time the request contents are updated, until either an "accept" or a "reject" rule matches, or the TCP request inspection delay expires with no matching rule. The first difference between these rules and "tcp-request connection" rules is that "tcp-request content" rules can make use of contents to take a decision. Most often, these decisions will consider a protocol recognition or validity. The second difference is that content-based rules can be used in both frontends and backends. In frontends, they will be evaluated upon new connections. In backends, they will be evaluated once a session is assigned a backend. This means that a single frontend connection may be evaluated several times by one or multiple backends when a session gets reassigned (for instance after a client-side HTTP keep-alive request). Content-based rules are evaluated in their exact declaration order. If no rule matches or if there is no rule, the default action is to accept the contents. There is no specific limit to the number of rules which may be inserted. Three types of actions are supported : - accept : - reject : - { track-sc1 | track-sc2 } <key> [table <table>] They have the same meaning as their counter-parts in "tcp-request connection" so please refer to that section for a complete description. Also, it is worth noting that if sticky counters are tracked from a rule defined in a backend, this tracking will automatically end when the session releases the backend. That allows per-backend counter tracking even in case of HTTP keep-alive requests when the backend changes. This makes a subtle difference because tracking rules in "frontend" and "listen" section last for all the session, as opposed to the backend rules. The difference appears when some layer 7 information is tracked. While there is nothing mandatory about it, it is recommended to use the track-sc1 pointer to track per-frontend counters and track-sc2 to track per-backend counters. Note that the "if/unless" condition is optional. If no condition is set on the action, it is simply performed unconditionally. That can be useful for "track-sc*" actions as well as for changing the default action to a reject. It is perfectly possible to match layer 7 contents with "tcp-request content" rules, since HTTP-specific ACL matches are able to preliminarily parse the contents of a buffer before extracting the required data. If the buffered contents do not parse as a valid HTTP message, then the ACL does not match. The parser which is involved there is exactly the same as for all other HTTP processing, so there is no risk of parsing something differently. Tracking layer7 information is also possible provided that the information are present when the rule is processed. The current solution for making the rule engine wait for such information is to set an inspect delay and to condition its execution with an ACL relying on such information.
Example:
# Accept HTTP requests containing a Host header saying "example.com"
# and reject everything else.
acl is_host_com hdr(Host) -i example.com
tcp-request inspect-delay 30s
tcp-request content accept if is_host_com
tcp-request content reject
Example:
# reject SMTP connection if client speaks first
tcp-request inspect-delay 30s
acl content_present req_len gt 0
tcp-request content reject if content_present
# Forward HTTPS connection only if client speaks
tcp-request inspect-delay 30s
acl content_present req_len gt 0
tcp-request content accept if content_present
tcp-request content reject
Example:
# Track the last IP from X-Forwarded-For
tcp-request inspect-delay 10s
tcp-request content track-sc1 hdr(x-forwarded-for,-1) if HTTP
Example:
# track request counts per "base" (concatenation of Host+URL)
tcp-request inspect-delay 10s
tcp-request content track-sc1 base table req-rate if HTTP
Example:
Track per-frontend and per-backend counters, block abusers at the frontend when the backend detects abuse.frontend http # Use General Purpose Couter 0 in SC1 as a global abuse counter # protecting all our sites stick-table type ip size 1m expire 5m store gpc0 tcp-request connection track-sc1 src tcp-request connection reject if { sc1_get_gpc0 gt 0 } ... use_backend http_dynamic if { path_end .php } backend http_dynamic # if a source makes too fast requests to this dynamic site (tracked # by SC2), block it globally in the frontend. stick-table type ip size 1m expire 5m store http_req_rate(10s) acl click_too_fast sc2_http_req_rate gt 10 acl mark_as_abuser sc1_inc_gpc0 gt 0 tcp-request content track-sc2 src tcp-request content reject if click_too_fast mark_as_abuser
See section 7 about ACL usage.
See also : "tcp-request connection", "tcp-request inspect-delay"
Set the maximum allowed time to wait for data during content inspection
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
People using haproxy primarily as a TCP relay are often worried about the risk of passing any type of protocol to a server without any analysis. In order to be able to analyze the request contents, we must first withhold the data then analyze them. This statement simply enables withholding of data for at most the specified amount of time. TCP content inspection applies very early when a connection reaches a frontend, then very early when the connection is forwarded to a backend. This means that a connection may experience a first delay in the frontend and a second delay in the backend if both have tcp-request rules. Note that when performing content inspection, haproxy will evaluate the whole rules for every new chunk which gets in, taking into account the fact that those data are partial. If no rule matches before the aforementioned delay, a last check is performed upon expiration, this time considering that the contents are definitive. If no delay is set, haproxy will not wait at all and will immediately apply a verdict based on the available information. Obviously this is unlikely to be very useful and might even be racy, so such setups are not recommended. As soon as a rule matches, the request is released and continues as usual. If the timeout is reached and no rule matches, the default policy will be to let it pass through unaffected. For most protocols, it is enough to set it to a few seconds, as most clients send the full request immediately upon connection. Add 3 or more seconds to cover TCP retransmits but that's all. For some protocols, it may make sense to use large values, for instance to ensure that the client never talks before the server (eg: SMTP), or to wait for a client to talk before passing data to the server (eg: SSL). Note that the client timeout must cover at least the inspection delay, otherwise it will expire first. If the client closes the connection or if the buffer is full, the delay immediately expires since the contents will not be able to change anymore.
See also : "tcp-request content accept", "tcp-request content reject", "timeout client".
Perform an action on a session response depending on a layer 4-7 condition
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<action> defines the action to perform if the condition applies. Valid
actions include : "accept", "reject".
See "tcp-request connection" above for their signification.
<condition> is a standard layer 4-7 ACL-based condition (see section 7).
Response contents can be analysed at an early stage of response processing
called "TCP content inspection". During this stage, ACL-based rules are
evaluated every time the response contents are updated, until either an
"accept" or a "reject" rule matches, or a TCP response inspection delay is
set and expires with no matching rule.
Most often, these decisions will consider a protocol recognition or validity.
Content-based rules are evaluated in their exact declaration order. If no
rule matches or if there is no rule, the default action is to accept the
contents. There is no specific limit to the number of rules which may be
inserted.
Two types of actions are supported :
- accept :
accepts the response if the condition is true (when used with "if")
or false (when used with "unless"). The first such rule executed ends
the rules evaluation.
- reject :
rejects the response if the condition is true (when used with "if")
or false (when used with "unless"). The first such rule executed ends
the rules evaluation. Rejected session are immediately closed.
Note that the "if/unless" condition is optional. If no condition is set on
the action, it is simply performed unconditionally. That can be useful for
for changing the default action to a reject.
It is perfectly possible to match layer 7 contents with "tcp-response
content" rules, but then it is important to ensure that a full response has
been buffered, otherwise no contents will match. In order to achieve this,
the best solution involves detecting the HTTP protocol during the inspection
period.
See section 7 about ACL usage.See also : "tcp-request content", "tcp-response inspect-delay"
Set the maximum allowed time to wait for a response during content inspection
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
See also : "tcp-response content", "tcp-request inspect-delay".
Set additional check timeout, but only after a connection has been already established.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments:
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
If set, haproxy uses min("timeout connect", "inter") as a connect timeout
for check and "timeout check" as an additional read timeout. The "min" is
used so that people running with *very* long "timeout connect" (eg. those
who needed this due to the queue or tarpit) do not slow down their checks.
(Please also note that there is no valid reason to have such long connect
timeouts, because "timeout queue" and "timeout tarpit" can always be used to
avoid that).
If "timeout check" is not set haproxy uses "inter" for complete check
timeout (connect + read) exactly like all <1.3.15 version.
In most cases check request is much simpler and faster to handle than normal
requests and people may want to kick out laggy servers so this timeout should
be smaller than "timeout server".
This parameter is specific to backends, but can be specified once for all in
"defaults" sections. This is in fact one of the easiest solutions not to
forget about it.
Set the maximum inactivity time on the client side.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The inactivity timeout applies when the client is expected to acknowledge or send data. In HTTP mode, this timeout is particularly important to consider during the first phase, when the client sends the request, and during the response while it is reading data sent by the server. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly recommended that the client timeout remains equal to the server timeout in order to avoid complex situations to debug. It is a good practice to cover one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds). If some long-lived sessions are mixed with short-lived sessions (eg: WebSocket and HTTP), it's worth considering "timeout tunnel", which overrides "timeout client" and "timeout server" for tunnels. This parameter is specific to frontends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of expired sessions in the system if the system's timeouts are not configured either. This parameter replaces the old, deprecated "clitimeout". It is recommended to use it to write new configurations. The form "timeout clitimeout" is provided only by backwards compatibility but its use is strongly discouraged.
Set the maximum time to wait for a connection attempt to a server to succeed.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
If the server is located on the same LAN as haproxy, the connection should be immediate (less than a few milliseconds). Anyway, it is a good practice to cover one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds). By default, the connect timeout also presets both queue and tarpit timeouts to the same value if these have not been specified. This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of failed sessions in the system if the system's timeouts are not configured either. This parameter replaces the old, deprecated "contimeout". It is recommended to use it to write new configurations. The form "timeout contimeout" is provided only by backwards compatibility but its use is strongly discouraged.
Set the maximum allowed time to wait for a new HTTP request to appear
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
By default, the time to wait for a new request in case of keep-alive is set by "timeout http-request". However this is not always convenient because some people want very short keep-alive timeouts in order to release connections faster, and others prefer to have larger ones but still have short timeouts once the request has started to present itself. The "http-keep-alive" timeout covers these needs. It will define how long to wait for a new HTTP request to start coming after a response was sent. Once the first byte of request has been seen, the "http-request" timeout is used to wait for the complete request to come. Note that empty lines prior to a new request do not refresh the timeout and are not counted as a new request. There is also another difference between the two timeouts : when a connection expires during timeout http-keep-alive, no error is returned, the connection just closes. If the connection expires in "http-request" while waiting for a connection to complete, a HTTP 408 error is returned. In general it is optimal to set this value to a few tens to hundreds of milliseconds, to allow users to fetch all objects of a page at once but without waiting for further clicks. Also, if set to a very small value (eg: 1 millisecond) it will probably only accept pipelined requests but not the non-pipelined ones. It may be a nice trade-off for very large sites running with tens to hundreds of thousands of clients. If this parameter is not set, the "http-request" timeout applies, and if both are not set, "timeout client" still applies at the lower level. It should be set in the frontend to take effect, unless the frontend is in TCP mode, in which case the HTTP backend's timeout will be used.
See also : "timeout http-request", "timeout client".
Set the maximum allowed time to wait for a complete HTTP request
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
In order to offer DoS protection, it may be required to lower the maximum accepted time to receive a complete HTTP request without affecting the client timeout. This helps protecting against established connections on which nothing is sent. The client timeout cannot offer a good protection against this abuse because it is an inactivity timeout, which means that if the attacker sends one character every now and then, the timeout will not trigger. With the HTTP request timeout, no matter what speed the client types, the request will be aborted if it does not complete in time. Note that this timeout only applies to the header part of the request, and not to any data. As soon as the empty line is received, this timeout is not used anymore. It is used again on keep-alive connections to wait for a second request if "timeout http-keep-alive" is not set. Generally it is enough to set it to a few seconds, as most clients send the full request immediately upon connection. Add 3 or more seconds to cover TCP retransmits but that's all. Setting it to very low values (eg: 50 ms) will generally work on local networks as long as there are no packet losses. This will prevent people from sending bare HTTP requests using telnet. If this parameter is not set, the client timeout still applies between each chunk of the incoming request. It should be set in the frontend to take effect, unless the frontend is in TCP mode, in which case the HTTP backend's timeout will be used.
See also : "timeout http-keep-alive", "timeout client".
Set the maximum time to wait in the queue for a connection slot to be free
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
When a server's maxconn is reached, connections are left pending in a queue which may be server-specific or global to the backend. In order not to wait indefinitely, a timeout is applied to requests pending in the queue. If the timeout is reached, it is considered that the request will almost never be served, so it is dropped and a 503 error is returned to the client. The "timeout queue" statement allows to fix the maximum time for a request to be left pending in a queue. If unspecified, the same value as the backend's connection timeout ("timeout connect") is used, for backwards compatibility with older versions with no "timeout queue" parameter.
See also : "timeout connect", "contimeout".
Set the maximum inactivity time on the server side.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The inactivity timeout applies when the server is expected to acknowledge or send data. In HTTP mode, this timeout is particularly important to consider during the first phase of the server's response, when it has to send the headers, as it directly represents the server's processing time for the request. To find out what value to put there, it's often good to start with what would be considered as unacceptable response times, then check the logs to observe the response time distribution, and adjust the value accordingly. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly recommended that the client timeout remains equal to the server timeout in order to avoid complex situations to debug. Whatever the expected server response times, it is a good practice to cover at least one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds minimum). If some long-lived sessions are mixed with short-lived sessions (eg: WebSocket and HTTP), it's worth considering "timeout tunnel", which overrides "timeout client" and "timeout server" for tunnels. This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of expired sessions in the system if the system's timeouts are not configured either. This parameter replaces the old, deprecated "srvtimeout". It is recommended to use it to write new configurations. The form "timeout srvtimeout" is provided only by backwards compatibility but its use is strongly discouraged.
Set the duration for which tarpitted connections will be maintained
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | yes |
Arguments :
<timeout> is the tarpit duration specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
When a connection is tarpitted using "reqtarpit", it is maintained open with no activity for a certain amount of time, then closed. "timeout tarpit" defines how long it will be maintained open. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. If unspecified, the same value as the backend's connection timeout ("timeout connect") is used, for backwards compatibility with older versions with no "timeout tarpit" parameter.
See also : "timeout connect", "contimeout".
Set the maximum inactivity time on the client and server side for tunnels.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The tunnel timeout applies when a bidirectional connection is established between a client and a server, and the connection remains inactive in both directions. This timeout supersedes both the client and server timeouts once the connection becomes a tunnel. In TCP, this timeout is used as soon as no analyser remains attached to either connection (eg: tcp content rules are accepted). In HTTP, this timeout is used when a connection is upgraded (eg: when switching to the WebSocket protocol, or forwarding a CONNECT request to a proxy), or after the first response when no keepalive/close option is specified. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. Whatever the expected normal idle time, it is a good practice to cover at least one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds minimum). This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it.
Example :
defaults http
option http-server-close
timeout connect 5s
timeout client 30s
timeout client 30s
timeout server 30s
timeout tunnel 1h # timeout to use with WebSocket and CONNECT
See also : "timeout client", "timeout server".
Enable client-side transparent proxying
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | no | yes | yes |
Arguments : none
This keyword was introduced in order to provide layer 7 persistence to layer 3 load balancers. The idea is to use the OS's ability to redirect an incoming connection for a remote address to a local process (here HAProxy), and let this process know what address was initially requested. When this option is used, sessions without cookies will be forwarded to the original destination IP address of the incoming request (which should match that of another equipment), while requests with cookies will still be forwarded to the appropriate server. The "transparent" keyword is deprecated, use "option transparent" instead. Note that contrary to a common belief, this option does NOT make HAProxy present the client's IP to the server when establishing the connection.
See also: "option transparent"
Generate a unique ID for each request.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<string> is a log-format string.
This keyword creates a ID for each request using the custom log format. A unique ID is useful to trace a request passing through many components of a complex infrastructure. The newly created ID may also be logged using the %ID tag the log-format string. The format should be composed from elements that are guaranteed to be unique when combined together. For instance, if multiple haproxy instances are involved, it might be important to include the node name. It is often needed to log the incoming connection's source and destination addresses and ports. Note that since multiple requests may be performed over the same connection, including a request counter may help differentiate them. Similarly, a timestamp may protect against a rollover of the counter. Logging the process ID will avoid collisions after a service restart. It is recommended to use hexadecimal notation for many fields since it makes them more compact and saves space in logs.
Example:
unique-id-format %{+X}o\ %Ci:%Cp_%Fi:%Fp_%Ts_%rt:%pid
will generate:
7F000001:8296_7F00001E:1F90_4F7B0A69_0003:790A
See also: "unique-id-header"
Add a unique ID header in the HTTP request.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| yes | yes | yes | no |
Arguments :
<name> is the name of the header.
Add a unique-id header in the HTTP request sent to the server, using the unique-id-format. It can't work if the unique-id-format doesn't exist.
Example:
unique-id-format %{+X}o\ %Ci:%Cp_%Fi:%Fp_%Ts_%rt:%pid
unique-id-header X-Unique-ID
will generate:
X-Unique-ID: 7F000001:8296_7F00001E:1F90_4F7B0A69_0003:790A
See also: "unique-id-format"
Switch to a specific backend if/unless an ACL-based condition is matched.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | yes | yes | no |
Arguments :
<backend> is the name of a valid backend or "listen" section. <condition> is a condition composed of ACLs, as described in section 7.
When doing content-switching, connections arrive on a frontend and are then dispatched to various backends depending on a number of conditions. The relation between the conditions and the backends is described with the "use_backend" keyword. While it is normally used with HTTP processing, it can also be used in pure TCP, either without content using stateless ACLs (eg: source address validation) or combined with a "tcp-request" rule to wait for some payload. There may be as many "use_backend" rules as desired. All of these rules are evaluated in their declaration order, and the first one which matches will assign the backend. In the first form, the backend will be used if the condition is met. In the second form, the backend will be used if the condition is not met. If no condition is valid, the backend defined with "default_backend" will be used. If no default backend is defined, either the servers in the same section are used (in case of a "listen" section) or, in case of a frontend, no server is used and a 503 service unavailable response is returned. Note that it is possible to switch from a TCP frontend to an HTTP backend. In this case, either the frontend has already checked that the protocol is HTTP, and backend processing will immediately follow, or the backend will wait for a complete HTTP request to get in. This feature is useful when a frontend must decode several protocols on a unique port, one of them being HTTP.
Only use a specific server if/unless an ACL-based condition is matched.
May be used in sections :
| defaults | frontend | listen | backend |
|---|---|---|---|
| no | no | yes | yes |
Arguments :
<server> is the name of a valid server in the same backend section. <condition> is a condition composed of ACLs, as described in section 7.
By default, connections which arrive to a backend are load-balanced across the available servers according to the configured algorithm, unless a persistence mechanism such as a cookie is used and found in the request. Sometimes it is desirable to forward a particular request to a specific server without having to declare a dedicated backend for this server. This can be achieved using the "use-server" rules. These rules are evaluated after the "redirect" rules and before evaluating cookies, and they have precedence on them. There may be as many "use-server" rules as desired. All of these rules are evaluated in their declaration order, and the first one which matches will assign the server. If a rule designates a server which is down, and "option persist" is not used and no force-persist rule was validated, it is ignored and evaluation goes on with the next rules until one matches. In the first form, the server will be used if the condition is met. In the second form, the server will be used if the condition is not met. If no condition is valid, the processing continues and the server will be assigned according to other persistence mechanisms. Note that even if a rule is matched, cookie processing is still performed but does not assign the server. This allows prefixed cookies to have their prefix stripped. The "use-server" statement works both in HTTP and TCP mode. This makes it suitable for use with content-based inspection. For instance, a server could be selected in a farm according to the TLS SNI field. And if these servers have their weight set to zero, they will not be used for other traffic.
Example :
# intercept incoming TLS requests based on the SNI field
use-server www if { req_ssl_sni -i www.example.com }
server www 192.168.0.1:443 weight 0
use-server mail if { req_ssl_sni -i mail.example.com }
server mail 192.168.0.1:587 weight 0
use-server imap if { req_ssl_sni -i imap.example.com }
server mail 192.168.0.1:993 weight 0
# all the rest is forwarded to this server
server default 192.168.0.2:443 check
See also: "use_backend", serction 5 about server and section 7 about ACLs.
5. Bind and Server options
The "bind", "server" and "default-server" keywords support a number of settings depending on some build options and on the system HAProxy was built on. These settings generally each consist in one word sometimes followed by a value, written on the same line as the "bind" or "server" line. All these options are described in this section.
5.1. Bind options
The "bind" keyword supports a certain number of settings which are all passed as arguments on the same line. The order in which those arguments appear makes no importance, provided that they appear after the bind address. All of these parameters are optional. Some of them consist in a single words (booleans), while other ones expect a value after them. In this case, the value must be provided immediately after the setting name. The currently supported settings are the following ones.
Enforces the use of the PROXY protocol over any connection accepted by any of the sockets declared on the same line. The PROXY protocol dictates the layer 3/4 addresses of the incoming connection to be used everywhere an address is used, with the only exception of "tcp-request connection" rules which will only see the real connection address. Logs will reflect the addresses indicated in the protocol, unless it is violated, in which case the real address will still be used. This keyword combined with support from external components can be used as an efficient and reliable alternative to the X-Forwarded-For mechanism which is not always reliable and not even always usable.
This enables the TLS ALPN extension and advertises the specified protocol list as supported on top of ALPN. The protocol list consists in a comma- delimited list of protocol names, for instance: "http/1.1,http/1.0" (without quotes). This requires that the SSL library is build with support for TLS extensions enabled (check with haproxy -vv). The ALPN extension replaces the initial NPN extension.
Sets the socket's backlog to this value. If unspecified, the frontend's backlog is used instead, which generally defaults to the maxconn value.
This setting is only available when support for OpenSSL was built in. It sets the named curve (RFC 4492) used to generate ECDH ephemeral keys. By default, used named curve is prime256v1.
This setting is only available when support for OpenSSL was built in. It designates a PEM file from which to load CA certificates used to verify client's certificate.
This setting is only available when support for OpenSSL was built in. Sets a comma separated list of errorIDs to ignore during verify at depth > 0. If set to 'all', all errors are ignored. SSL handshake is not aborted if an error is ignored.
This setting is only available when support for OpenSSL was built in. It sets
the string describing the list of cipher algorithms ("cipher suite") that are
negociated during the SSL/TLS handshake. The format of the string is defined
in "man 1 ciphers" from OpenSSL man pages, and can be for instance a string
such as "AES:ALL:!aNULL:!eNULL:+RC4:@STRENGTH" (without quotes).This setting is only available when support for OpenSSL was built in. It designates a PEM file from which to load certificate revocation list used to verify client's certificate.
This setting is only available when support for OpenSSL was built in. It designates a PEM file containing both the required certificates and any associated private keys. This file can be built by concatenating multiple PEM files into one (e.g. cat cert.pem key.pem > combined.pem). If your CA requires an intermediate certificate, this can also be concatenated into this file. If the OpenSSL used supports Diffie-Hellman, parameters present in this file are loaded. If a directory name is used instead of a PEM file, then all files found in that directory will be loaded. This directive may be specified multiple times in order to load certificates from multiple files or directories. The certificates will be presented to clients who provide a valid TLS Server Name Indication field matching one of their CN or alt subjects. Wildcards are supported, where a wildcard character '*' is used instead of the first hostname component (eg: *.example.org matches www.example.org but not www.sub.example.org). If no SNI is provided by the client or if the SSL library does not support TLS extensions, or if the client provides an SNI hostname which does not match any certificate, then the first loaded certificate will be presented. This means that when loading certificates from a directory, it is highly recommended to load the default one first as a file. Note that the same cert may be loaded multiple times without side effects. Some CAs (such as Godaddy) offer a drop down list of server types that do not include HAProxy when obtaining a certificate. If this happens be sure to choose a webserver that the CA believes requires a intermediate CA (for Godaddy, selection Apache Tomcat will get the correct bundle, but many others, e.g. nginx, result in a wrong bundle that will not work for some clients).
This setting is only available when support for OpenSSL was built in. Sets a comma separated list of errorIDs to ignore during verify at depth == 0. If set to 'all', all errors are ignored. SSL handshake is not abored if an error is ignored.
This setting is only available when support for OpenSSL was built in. It
designates a list of PEM file with an optional list of SNI filter per
certificate, with the following format for each line :
<crtfile> [[!]<snifilter> ...]
Wildcards are supported in the SNI filter. Negative filter are also supported,
only useful in combination with a wildcard filter to exclude a particular SNI.
The certificates will be presented to clients who provide a valid TLS Server
Name Indication field matching one of the SNI filters. If no SNI filter is
specified, the CN and alt subjects are used. This directive may be specified
multiple times. See the "crt" option for more information. The default
certificate is still needed to meet OpenSSL expectations. If it is not used,
the 'strict-sni' option may be used.Is an optional keyword which is supported only on certain Linux kernels. It states that a connection will only be accepted once some data arrive on it, or at worst after the first retransmit. This should be used only on protocols for which the client talks first (eg: HTTP). It can slightly improve performance by ensuring that most of the request is already available when the connection is accepted. On the other hand, it will not be able to detect connections which don't talk. It is important to note that this option is broken in all kernels up to 2.6.31, as the connection is never accepted until the client talks. This can cause issues with front firewalls which would see an established connection while the proxy will only see it in SYN_RECV. This option is only supported on TCPv4/TCPv6 sockets and ignored by other ones.
This option enforces use of SSLv3 only on SSL connections instanciated from this listener. SSLv3 is generally less expensive than the TLS counterparts for high connection rates. See also "force-tls*", "no-sslv3", and "no-tls*".
This option enforces use of TLSv1.0 only on SSL connections instanciated from this listener. See also "force-tls*", "no-sslv3", and "no-tls*".
This option enforces use of TLSv1.1 only on SSL connections instanciated from this listener. See also "force-tls*", "no-sslv3", and "no-tls*".
This option enforces use of TLSv1.2 only on SSL connections instanciated from this listener. See also "force-tls*", "no-sslv3", and "no-tls*".
Sets the group of the UNIX sockets to the designated system gid. It can also be set by default in the global section's "unix-bind" statement. Note that some platforms simply ignore this. This setting is equivalent to the "group" setting except that the group ID is used instead of its name. This setting is ignored by non UNIX sockets.
Sets the group of the UNIX sockets to the designated system group. It can also be set by default in the global section's "unix-bind" statement. Note that some platforms simply ignore this. This setting is equivalent to the "gid" setting except that the group name is used instead of its gid. This setting is ignored by non UNIX sockets.
Fixes the socket ID. By default, socket IDs are automatically assigned, but sometimes it is more convenient to fix them to ease monitoring. This value must be strictly positive and unique within the listener/frontend. This option can only be used when defining only a single socket.
Restricts the socket to a specific interface. When specified, only packets received from that particular interface are processed by the socket. This is currently only supported on Linux. The interface must be a primary system interface, not an aliased interface. It is also possible to bind multiple frontends to the same address if they are bound to different interfaces. Note that binding to a network interface requires root privileges. This parameter is only compatible with TCPv4/TCPv6 sockets.
This setting is used with the stats sockets only to restrict the nature of
the commands that can be issued on the socket. It is ignored by other
sockets. <level> can be one of :
- "user" is the least privileged level ; only non-sensitive stats can be
read, and no change is allowed. It would make sense on systems where it
is not easy to restrict access to the socket.
- "operator" is the default level and fits most common uses. All data can
be read, and only non-sensitive changes are permitted (eg: clear max
counters).
- "admin" should be used with care, as everything is permitted (eg: clear
all counters).Limits the sockets to this number of concurrent connections. Extraneous connections will remain in the system's backlog until a connection is released. If unspecified, the limit will be the same as the frontend's maxconn. Note that in case of port ranges or multiple addresses, the same value will be applied to each socket. This setting enables different limitations on expensive sockets, for instance SSL entries which may easily eat all memory.
Sets the octal mode used to define access permissions on the UNIX socket. It can also be set by default in the global section's "unix-bind" statement. Note that some platforms simply ignore this. This setting is ignored by non UNIX sockets.
Sets the TCP Maximum Segment Size (MSS) value to be advertised on incoming connections. This can be used to force a lower MSS for certain specific ports, for instance for connections passing through a VPN. Note that this relies on a kernel feature which is theoretically supported under Linux but was buggy in all versions prior to 2.6.28. It may or may not work on other operating systems. It may also not change the advertised value but change the effective size of outgoing segments. The commonly advertised value for TCPv4 over Ethernet networks is 1460 = 1500(MTU) - 40(IP+TCP). If this value is positive, it will be used as the advertised MSS. If it is negative, it will indicate by how much to reduce the incoming connection's advertised MSS for outgoing segments. This parameter is only compatible with TCP v4/v6 sockets.
Sets an optional name for these sockets, which will be reported on the stats page.
Sets the 'niceness' of connections initiated from the socket. Value must be in the range -1024..1024 inclusive, and defaults to zero. Positive values means that such connections are more friendly to others and easily offer their place in the scheduler. On the opposite, negative values mean that connections want to run with a higher priority than others. The difference only happens under high loads when the system is close to saturation. Negative values are appropriate for low-latency or administration services, and high values are generally recommended for CPU intensive tasks such as SSL processing or bulk transfers which are less sensible to latency. For example, it may make sense to use a positive value for an SMTP socket and a negative one for an RDP socket.
This setting is only available when support for OpenSSL was built in. It disables support for SSLv3 on any sockets instanciated from the listener when SSL is supported. Note that SSLv2 is forced disabled in the code and cannot be enabled using any configuration option. See also "force-tls*", and "force-sslv3".
This setting is only available when support for OpenSSL was built in. It disables the stateless session resumption (RFC 5077 TLS Ticket extension) and force to use stateful session resumption. Stateless session resumption is more expensive in CPU usage.
This setting is only available when support for OpenSSL was built in. It disables support for TLSv1.0 on any sockets instanciated from the listener when SSL is supported. Note that SSLv2 is forced disabled in the code and cannot be enabled using any configuration option. See also "force-tls*", and "force-sslv3".
This setting is only available when support for OpenSSL was built in. It disables support for TLSv1.1 on any sockets instanciated from the listener when SSL is supported. Note that SSLv2 is forced disabled in the code and cannot be enabled using any configuration option. See also "force-tls*", and "force-sslv3".
This setting is only available when support for OpenSSL was built in. It disables support for TLSv1.2 on any sockets instanciated from the listener when SSL is supported. Note that SSLv2 is forced disabled in the code and cannot be enabled using any configuration option. See also "force-tls*", and "force-sslv3".
This enables the NPN TLS extension and advertises the specified protocol list as supported on top of NPN. The protocol list consists in a comma-delimited list of protocol names, for instance: "http/1.1,http/1.0" (without quotes). This requires that the SSL library is build with support for TLS extensions enabled (check with haproxy -vv). Note that the NPN extension has been replaced with the ALPN extension (see the "alpn" keyword).
This setting is only available when support for OpenSSL was built in. It enables SSL deciphering on connections instanciated from this listener. A certificate is necessary (see "crt" above). All contents in the buffers will appear in clear text, so that ACLs and HTTP processing will only have access to deciphered contents.
This setting is only available when support for OpenSSL was built in. The SSL/TLS negotiation is allow only if the client provided an SNI which match a certificate. The default certificate is not used. See the "crt" option for more information.
Is an optional keyword which is supported only on Linux kernels >= 3.7. It enables TCP Fast Open on the listening socket, which means that clients which support this feature will be able to send a request and receive a response during the 3-way handshake starting from second connection, thus saving one round-trip after the first connection. This only makes sense with protocols that use high connection rates and where each round trip matters. This can possibly cause issues with many firewalls which do not accept data on SYN packets, so this option should only be enabled once well tested. This option is only supported on TCPv4/TCPv6 sockets and ignored by other ones. You may need to build HAProxy with USE_TFO=1 if your libc doesn't define TCP_FASTOPEN.
Is an optional keyword which is supported only on certain Linux kernels. It indicates that the addresses will be bound even if they do not belong to the local machine, and that packets targeting any of these addresses will be intercepted just as if the addresses were locally configured. This normally requires that IP forwarding is enabled. Caution! do not use this with the default address '*', as it would redirect any traffic for the specified port. This keyword is available only when HAProxy is built with USE_LINUX_TPROXY=1. This parameter is only compatible with TCPv4 and TCPv6 sockets, depending on kernel version. Some distribution kernels include backports of the feature, so check for support with your vendor.
Is an optional keyword which is supported only on most recent systems including Linux kernels >= 2.4.21. It is used to bind a socket to both IPv4 and IPv6 when it uses the default address. Doing so is sometimes necessary on systems which bind to IPv6 only by default. It has no effect on non-IPv6 sockets, and is overriden by the "v6only" option.
Is an optional keyword which is supported only on most recent systems including Linux kernels >= 2.4.21. It is used to bind a socket to IPv6 only when it uses the default address. Doing so is sometimes preferred to doing it system-wide as it is per-listener. It has no effect on non-IPv6 sockets and has precedence over the "v4v6" option.
Sets the owner of the UNIX sockets to the designated system uid. It can also be set by default in the global section's "unix-bind" statement. Note that some platforms simply ignore this. This setting is equivalent to the "user" setting except that the user numeric ID is used instead of its name. This setting is ignored by non UNIX sockets.
Sets the owner of the UNIX sockets to the designated system user. It can also be set by default in the global section's "unix-bind" statement. Note that some platforms simply ignore this. This setting is equivalent to the "uid" setting except that the user name is used instead of its uid. This setting is ignored by non UNIX sockets.
This setting is only available when support for OpenSSL was built in. If set to 'none', client certificate is not requested. This is the default. In other cases, a client certificate is requested. If the client does not provide a certificate after the request and if 'verify' is set to 'required', then the handshake is aborted, while it would have succeeded if set to 'optional'. The certificate provided by the client is always verified using CAs from 'ca-file' and optional CRLs from 'crl-file'. On verify failure the handshake is aborted, regardless of the 'verify' option, unless the error code exactly matches one of those listed with 'ca-ignore-err' or 'crt-ignore-err'.
5.2. Server and default-server options
The "server" and "default-server" keywords support a certain number of settings which are all passed as arguments on the server line. The order in which those arguments appear does not count, and they are all optional. Some of those settings are single words (booleans) while others expect one or several values after them. In this case, the values must immediately follow the setting name. Except default-server, all those settings must be specified after the server's address if they are used: server <name> <address>[:port] [settings ...] default-server [settings ...] The currently supported settings are the following ones.
Using the "addr" parameter, it becomes possible to use a different IP address to send health-checks. On some servers, it may be desirable to dedicate an IP address to specific component able to perform complex tests which are more suitable to health-checks than the application. This parameter is ignored if the "check" parameter is not set. See also the "port" parameter. Supported in default-server: No
When "backup" is present on a server line, the server is only used in load balancing when all other non-backup servers are unavailable. Requests coming with a persistence cookie referencing the server will always be served though. By default, only the first operational backup server is used, unless the "allbackups" option is set in the backend. See also the "allbackups" option. Supported in default-server: No
This setting is only available when support for OpenSSL was built in. It designates a PEM file from which to load CA certificates used to verify server's certificate. Supported in default-server: No
This option enables health checks on the server. By default, a server is always considered available. If "check" is set, the server is available when accepting periodic TCP connections, to ensure that it is really able to serve requests. The default address and port to send the tests to are those of the server, and the default source is the same as the one defined in the backend. It is possible to change the address using the "addr" parameter, the port using the "port" parameter, the source address using the "source" address, and the interval and timers using the "inter", "rise" and "fall" parameters. The request method is define in the backend using the "httpchk", "lb-agent-chk", "smtpchk", "mysql-check", "pgsql-check" and "ssl-hello-chk" options. Please refer to those options and parameters for more information. Supported in default-server: No
This option forces emission of a PROXY protocol line with outgoing health checks, regardless of whether the server uses send-proxy or not for the normal traffic. By default, the PROXY protocol is enabled for health checks if it is already enabled for normal traffic and if no "port" nor "addr" directive is present. However, if such a directive is present, the "check-send-proxy" option needs to be used to force the use of the protocol. See also the "send-proxy" option for more information. Supported in default-server: No
This option forces encryption of all health checks over SSL, regardless of whether the server uses SSL or not for the normal traffic. This is generally used when an explicit "port" or "addr" directive is specified and SSL health checks are not inherited. It is important to understand that this option inserts an SSL transport layer below the ckecks, so that a simple TCP connect check becomes an SSL connect, which replaces the old ssl-hello-chk. The most common use is to send HTTPS checks by combining "httpchk" with SSL checks. All SSL settings are common to health checks and traffic (eg: ciphers). See the "ssl" option for more information. Supported in default-server: No
This option sets the string describing the list of cipher algorithms that is is negociated during the SSL/TLS handshake with the server. The format of the string is defined in "man 1 ciphers". When SSL is used to communicate with servers on the local network, it is common to see a weaker set of algorithms than what is used over the internet. Doing so reduces CPU usage on both the server and haproxy while still keeping it compatible with deployed software. Some algorithms such as RC4-SHA1 are reasonably cheap. If no security at all is needed and just connectivity, using DES can be appropriate. Supported in default-server: No
The "cookie" parameter sets the cookie value assigned to the server to <value>. This value will be checked in incoming requests, and the first operational server possessing the same value will be selected. In return, in cookie insertion or rewrite modes, this value will be assigned to the cookie sent to the client. There is nothing wrong in having several servers sharing the same cookie value, and it is in fact somewhat common between normal and backup servers. See also the "cookie" keyword in backend section. Supported in default-server: No
This setting is only available when support for OpenSSL was built in. It designates a PEM file from which to load certificate revocation list used to verify server's certificate. Supported in default-server: No
This setting is only available when support for OpenSSL was built in. It designates a PEM file from which to load both a certificate and the associated private key. This file can be built by concatenating both PEM files into one. This certificate will be sent if the server send a client certificate request. Supported in default-server: No
The "disabled" keyword starts the server in the "disabled" state. That means that it is marked down in maintenance mode, and no connection other than the ones allowed by persist mode will reach it. It is very well suited to setup new servers, because normal traffic will never reach them, while it is still possible to test the service by making use of the force-persist mechanism. Supported in default-server: No
If health observing is enabled, the "error-limit" parameter specifies the number of consecutive errors that triggers event selected by the "on-error" option. By default it is set to 10 consecutive errors. Supported in default-server: Yes See also the "check", "error-limit" and "on-error".
The "fall" parameter states that a server will be considered as dead after <count> consecutive unsuccessful health checks. This value defaults to 3 if unspecified. See also the "check", "inter" and "rise" parameters. Supported in default-server: Yes
This option enforces use of SSLv3 only when SSL is used to communicate with the server. SSLv3 is generally less expensive than the TLS counterparts for high connection rates. See also "no-tlsv*", "no-sslv3". Supported in default-server: No
This option enforces use of TLSv1.0 only when SSL is used to communicate with the server. See also "no-tlsv*", "no-sslv3". Supported in default-server: No
This option enforces use of TLSv1.1 only when SSL is used to communicate with the server. See also "no-tlsv*", "no-sslv3". Supported in default-server: No
This option enforces use of TLSv1.2 only when SSL is used to communicate with the server. See also "no-tlsv*", "no-sslv3". Supported in default-server: No
Set a persistent ID for the server. This ID must be positive and unique for the proxy. An unused ID will automatically be assigned if unset. The first assigned value will be 1. This ID is currently only returned in statistics. Supported in default-server: No
The "inter" parameter sets the interval between two consecutive health checks to <delay> milliseconds. If left unspecified, the delay defaults to 2000 ms. It is also possible to use "fastinter" and "downinter" to optimize delays between checks depending on the server state :
| Server state | Interval used |
|---|---|
| UP 100% (non-transitional) | "inter" |
| Transitionally UP (going down), Transitionally DOWN (going up), or yet unchecked. | "fastinter" if set, "inter" otherwise. |
| DOWN 100% (non-transitional) | "downinter" if set, "inter" otherwise. |
Just as with every other time-based parameter, they can be entered in any
other explicit unit among { us, ms, s, m, h, d }. The "inter" parameter also
serves as a timeout for health checks sent to servers if "timeout check" is
not set. In order to reduce "resonance" effects when multiple servers are
hosted on the same hardware, the health-checks of all servers are started
with a small time offset between them. It is also possible to add some random
noise in the health checks interval using the global "spread-checks"
keyword. This makes sense for instance when a lot of backends use the same
servers.
Supported in default-server: YesThe "maxconn" parameter specifies the maximal number of concurrent connections that will be sent to this server. If the number of incoming concurrent requests goes higher than this value, they will be queued, waiting for a connection to be released. This parameter is very important as it can save fragile servers from going down under extreme loads. If a "minconn" parameter is specified, the limit becomes dynamic. The default value is "0" which means unlimited. See also the "minconn" and "maxqueue" parameters, and the backend's "fullconn" keyword. Supported in default-server: Yes
The "maxqueue" parameter specifies the maximal number of connections which will wait in the queue for this server. If this limit is reached, next requests will be redispatched to other servers instead of indefinitely waiting to be served. This will break persistence but may allow people to quickly re-log in when the server they try to connect to is dying. The default value is "0" which means the queue is unlimited. See also the "maxconn" and "minconn" parameters. Supported in default-server: Yes
When the "minconn" parameter is set, the maxconn limit becomes a dynamic limit following the backend's load. The server will always accept at least <minconn> connections, never more than <maxconn>, and the limit will be on the ramp between both values when the backend has less than <fullconn> concurrent connections. This makes it possible to limit the load on the server during normal loads, but push it further for important loads without overloading the server during exceptional loads. See also the "maxconn" and "maxqueue" parameters, as well as the "fullconn" backend keyword. Supported in default-server: Yes
This option disables support for SSLv3 when SSL is used to communicate with the server. Note that SSLv2 is disabled in the code and cannot be enabled using any configuration option. See also "force-sslv3", "force-tlsv*". Supported in default-server: No
This setting is only available when support for OpenSSL was built in. It disables the stateless session resumption (RFC 5077 TLS Ticket extension) and force to use stateful session resumption. Stateless session resumption is more expensive in CPU usage for servers. Supported in default-server: No
This option disables support for TLSv1.0 when SSL is used to communicate with the server. Note that SSLv2 is disabled in the code and cannot be enabled using any configuration option. TLSv1 is more expensive than SSLv3 so it often makes sense to disable it when communicating with local servers. See also "force-sslv3", "force-tlsv*". Supported in default-server: No
This option disables support for TLSv1.1 when SSL is used to communicate with the server. Note that SSLv2 is disabled in the code and cannot be enabled using any configuration option. TLSv1 is more expensive than SSLv3 so it often makes sense to disable it when communicating with local servers. See also "force-sslv3", "force-tlsv*". Supported in default-server: No
This option disables support for TLSv1.2 when SSL is used to communicate with the server. Note that SSLv2 is disabled in the code and cannot be enabled using any configuration option. TLSv1 is more expensive than SSLv3 so it often makes sense to disable it when communicating with local servers. See also "force-sslv3", "force-tlsv*". Supported in default-server: No
Never add connections allocated to this sever to a stick-table. This may be used in conjunction with backup to ensure that stick-table persistence is disabled for backup servers. Supported in default-server: No
This option enables health adjusting based on observing communication with the server. By default this functionality is disabled and enabling it also requires to enable health checks. There are two supported modes: "layer4" and "layer7". In layer4 mode, only successful/unsuccessful tcp connections are significant. In layer7, which is only allowed for http proxies, responses received from server are verified, like valid/wrong http code, unparsable headers, a timeout, etc. Valid status codes include 100 to 499, 501 and 505. Supported in default-server: No See also the "check", "on-error" and "error-limit".
Select what should happen when enough consecutive errors are detected. Currently, four modes are available: - fastinter: force fastinter - fail-check: simulate a failed check, also forces fastinter (default) - sudden-death: simulate a pre-fatal failed health check, one more failed check will mark a server down, forces fastinter - mark-down: mark the server immediately down and force fastinter Supported in default-server: Yes See also the "check", "observe" and "error-limit".
Modify what occurs when a server is marked down. Currently one action is available: - shutdown-sessions: Shutdown peer sessions. When this setting is enabled, all connections to the server are immediately terminated when the server goes down. It might be used if the health check detects more complex cases than a simple connection status, and long timeouts would cause the service to remain unresponsive for too long a time. For instance, a health check might detect that a database is stuck and that there's no chance to reuse existing connections anymore. Connections killed this way are logged with a 'D' termination code (for "Down"). Actions are disabled by default Supported in default-server: Yes
Modify what occurs when a server is marked up. Currently one action is available: - shutdown-backup-sessions: Shutdown sessions on all backup servers. This is done only if the server is not in backup state and if it is not disabled (it must have an effective weight > 0). This can be used sometimes to force an active server to take all the traffic back after recovery when dealing with long sessions (eg: LDAP, SQL, ...). Doing this can cause more trouble than it tries to solve (eg: incomplete transactions), so use this feature with extreme care. Sessions killed because a server comes up are logged with an 'U' termination code (for "Up"). Actions are disabled by default Supported in default-server: Yes
Using the "port" parameter, it becomes possible to use a different port to send health-checks. On some servers, it may be desirable to dedicate a port to a specific component able to perform complex tests which are more suitable to health-checks than the application. It is common to run a simple script in inetd for instance. This parameter is ignored if the "check" parameter is not set. See also the "addr" parameter. Supported in default-server: Yes
The "redir" parameter enables the redirection mode for all GET and HEAD requests addressing this server. This means that instead of having HAProxy forward the request to the server, it will send an "HTTP 302" response with the "Location" header composed of this prefix immediately followed by the requested URI beginning at the leading '/' of the path component. That means that no trailing slash should be used after <prefix>. All invalid requests will be rejected, and all non-GET or HEAD requests will be normally served by the server. Note that since the response is completely forged, no header mangling nor cookie insertion is possible in the response. However, cookies in requests are still analysed, making this solution completely usable to direct users to a remote location in case of local disaster. Main use consists in increasing bandwidth for static servers by having the clients directly connect to them. Note: never use a relative location here, it would cause a loop between the client and HAProxy!
Example :
server srv1 192.168.1.1:80 redir http://image1.mydomain.com check
Supported in default-server: No
The "rise" parameter states that a server will be considered as operational after <count> consecutive successful health checks. This value defaults to 2 if unspecified. See also the "check", "inter" and "fall" parameters. Supported in default-server: Yes
The "send-proxy" parameter enforces use of the PROXY protocol over any connection established to this server. The PROXY protocol informs the other end about the layer 3/4 addresses of the incoming connection, so that it can know the client's address or the public address it accessed to, whatever the upper layer protocol. For connections accepted by an "accept-proxy" listener, the advertised address will be used. Only TCPv4 and TCPv6 address families are supported. Other families such as Unix sockets, will report an UNKNOWN family. Servers using this option can fully be chained to another instance of haproxy listening with an "accept-proxy" setting. This setting must not be used if the server isn't aware of the protocol. When health checks are sent to the server, the PROXY protocol is automatically used when this option is set, unless there is an explicit "port" or "addr" directive, in which case an explicit "check-send-proxy" directive would also be needed to use the PROXY protocol. See also the "accept-proxy" option of the "bind" keyword. Supported in default-server: No
The "slowstart" parameter for a server accepts a value in milliseconds which indicates after how long a server which has just come back up will run at full speed. Just as with every other time-based parameter, it can be entered in any other explicit unit among { us, ms, s, m, h, d }. The speed grows linearly from 0 to 100% during this time. The limitation applies to two parameters : - maxconn: the number of connections accepted by the server will grow from 1 to 100% of the usual dynamic limit defined by (minconn,maxconn,fullconn). - weight: when the backend uses a dynamic weighted algorithm, the weight grows linearly from 1 to 100%. In this case, the weight is updated at every health-check. For this reason, it is important that the "inter" parameter is smaller than the "slowstart", in order to maximize the number of steps. The slowstart never applies when haproxy starts, otherwise it would cause trouble to running servers. It only applies when a server has been previously seen as failed. Supported in default-server: Yes
The "source" parameter sets the source address which will be used when connecting to the server. It follows the exact same parameters and principle as the backend "source" keyword, except that it only applies to the server referencing it. Please consult the "source" keyword for details. Additionally, the "source" statement on a server line allows one to specify a source port range by indicating the lower and higher bounds delimited by a dash ('-'). Some operating systems might require a valid IP address when a source port range is specified. It is permitted to have the same IP/range for several servers. Doing so makes it possible to bypass the maximum of 64k total concurrent connections. The limit will then reach 64k connections per server. Supported in default-server: No
This option enables SSL ciphering on outgoing connections to the server. At the moment, server certificates are not checked, so this is prone to man in the middle attacks. The real intended use is to permit SSL communication with software which cannot work in other modes over networks that would otherwise be considered safe enough for clear text communications. When this option is used, health checks are automatically sent in SSL too unless there is a "port" or an "addr" directive indicating the check should be sent to a different location. See the "check-ssl" optino to force SSL health checks. Supported in default-server: No
This option enables ability to set the current state of the server by tracking another one. Only a server with checks enabled can be tracked so it is not possible for example to track a server that tracks another one. If <proxy> is omitted the current one is used. If disable-on-404 is used, it has to be enabled on both proxies. Supported in default-server: No
This setting is only available when support for OpenSSL was built in. If set to 'none', server certificate is not verified. This is the default. In the other case, The certificate provided by the server is verified using CAs from 'ca-file' and optional CRLs from 'crl-file'. On verify failure the handshake is aborted. Supported in default-server: No
The "weight" parameter is used to adjust the server's weight relative to other servers. All servers will receive a load proportional to their weight relative to the sum of all weights, so the higher the weight, the higher the load. The default weight is 1, and the maximal value is 256. A value of 0 means the server will not participate in load-balancing but will still accept persistent connections. If this parameter is used to distribute the load according to server's capacity, it is recommended to start with values which can both grow and shrink, for instance between 10 and 100 to leave enough room above and below for later adjustments. Supported in default-server: Yes
6. HTTP header manipulation
In HTTP mode, it is possible to rewrite, add or delete some of the request and response headers based on regular expressions. It is also possible to block a request or a response if a particular header matches a regular expression, which is enough to stop most elementary protocol attacks, and to protect against information leak from the internal network. But there is a limitation to this : since HAProxy's HTTP engine does not support keep-alive, only headers passed during the first request of a TCP session will be seen. All subsequent headers will be considered data only and not analyzed. Furthermore, HAProxy never touches data contents, it stops analysis at the end of headers. There is an exception though. If HAProxy encounters an "Informational Response" (status code 1xx), it is able to process all rsp* rules which can allow, deny, rewrite or delete a header, but it will refuse to add a header to any such messages as this is not HTTP-compliant. The reason for still processing headers in such responses is to stop and/or fix any possible information leak which may happen, for instance because another downstream equipment would unconditionally add a header, or if a server name appears there. When such messages are seen, normal processing still occurs on the next non-informational messages. This section covers common usage of the following keywords, described in detail in section 4.2 : - reqadd <string> - reqallow <search> - reqiallow <search> - reqdel <search> - reqidel <search> - reqdeny <search> - reqideny <search> - reqpass <search> - reqipass <search> - reqrep <search> <replace> - reqirep <search> <replace> - reqtarpit <search> - reqitarpit <search> - rspadd <string> - rspdel <search> - rspidel <search> - rspdeny <search> - rspideny <search> - rsprep <search> <replace> - rspirep <search> <replace> With all these keywords, the same conventions are used. The <search> parameter is a POSIX extended regular expression (regex) which supports grouping through parenthesis (without the backslash). Spaces and other delimiters must be prefixed with a backslash ('\') to avoid confusion with a field delimiter. Other characters may be prefixed with a backslash to change their meaning : \t for a tab \r for a carriage return (CR) \n for a new line (LF) \ to mark a space and differentiate it from a delimiter \# to mark a sharp and differentiate it from a comment \\ to use a backslash in a regex \\\\ to use a backslash in the text (*2 for regex, *2 for haproxy) \xXX to write the ASCII hex code XX as in the C language The <replace> parameter contains the string to be used to replace the largest portion of text matching the regex. It can make use of the special characters above, and can reference a substring which is delimited by parenthesis in the regex, by writing a backslash ('\') immediately followed by one digit from 0 to 9 indicating the group position (0 designating the entire line). This practice is very common to users of the "sed" program. The <string> parameter represents the string which will systematically be added after the last header line. It can also use special character sequences above.
Notes related to these keywords :
- these keywords are not always convenient to allow/deny based on header contents. It is strongly recommended to use ACLs with the "block" keyword instead, resulting in far more flexible and manageable rules. - lines are always considered as a whole. It is not possible to reference a header name only or a value only. This is important because of the way headers are written (notably the number of spaces after the colon). - the first line is always considered as a header, which makes it possible to rewrite or filter HTTP requests URIs or response codes, but in turn makes it harder to distinguish between headers and request line. The regex prefix ^[^\ \t]*[\ \t] matches any HTTP method followed by a space, and the prefix ^[^ \t:]*: matches any header name followed by a colon. - for performances reasons, the number of characters added to a request or to a response is limited at build time to values between 1 and 4 kB. This should normally be far more than enough for most usages. If it is too short on occasional usages, it is possible to gain some space by removing some useless headers before adding new ones. - keywords beginning with "reqi" and "rspi" are the same as their counterpart without the 'i' letter except that they ignore case when matching patterns. - when a request passes through a frontend then a backend, all req* rules from the frontend will be evaluated, then all req* rules from the backend will be evaluated. The reverse path is applied to responses. - req* statements are applied after "block" statements, so that "block" is always the first one, but before "use_backend" in order to permit rewriting before switching.
7. Using ACLs and pattern extraction
The use of Access Control Lists (ACL) provides a flexible solution to perform content switching and generally to take decisions based on content extracted from the request, the response or any environmental status. The principle is simple : - define test criteria with sets of values - perform actions only if a set of tests is valid The actions generally consist in blocking the request, or selecting a backend. In order to define a test, the "acl" keyword is used. The syntax is : acl <aclname> <criterion> [flags] [operator] <value> ... This creates a new ACL <aclname> or completes an existing one with new tests. Those tests apply to the portion of request/response specified in <criterion> and may be adjusted with optional flags [flags]. Some criteria also support an operator which may be specified before the set of values. The values are of the type supported by the criterion, and are separated by spaces. ACL names must be formed from upper and lower case letters, digits, '-' (dash), '_' (underscore) , '.' (dot) and ':' (colon). ACL names are case-sensitive, which means that "my_acl" and "My_Acl" are two different ACLs. There is no enforced limit to the number of ACLs. The unused ones do not affect performance, they just consume a small amount of memory. The following ACL flags are currently supported : -i : ignore case during matching of all subsequent patterns. -f : load patterns from a file. -m : changes the pattern matching method -- : force end of flags. Useful when a string looks like one of the flags. The "-m" flag is special. It allows the default pattern matching method to be changed for the fetched sample. The default method depends on the keyword and is described later in this document. When "-m" is specified and followed by a pattern matching method name, this method is used instead. This makes it possible to match contents in ways that were not initially planned. There are some restrictions however. Not all methods can be used with all sample fetch methods. Also, if "-m" is used in conjunction with "-f", it must be placed first. The pattern matching method must be one of the following : - "found" : only check if the requested sample could be found in the stream, but do not compare it against any pattern. It is recommended not to pass any pattern to avoid any confusion. This matching method is particularly useful to detect presence of certain contents such as headers, cookies, etc... even if they are empty and without comparing them to anything nor counting them. - "bool" : check the value as a boolean. It can only be applied to fetches which return a boolean or integer value, and takes no pattern. Value zero does not match, all other values do match. - "int" : match the value as an integer. It can be used with integer and boolean samples. - "ip" : match the value as an IPv4 or IPv6 address. It is compatible with IP addresse only. - "bin" : match the contents against an hexadecimal string representing a binary sequence. This may be used with binary or string samples. - "len" : match the sample's length as an integer. This may be used with binary or string samples. - "str" : match the contents against a string. This may be used with binary or string samples. - "beg" : check that the contents begin like the provided string patterns. This may be used with binary or string samples. - "sub" : check that the contents contain at least one of the provided string patterns. This may be used with binary or string samples. - "dir" : check that a slash-delimited portion of the contents exactly match one of the provided string patterns. This may be used with binary or string samples. - "dom" : check that a dot-delimited portion of the contents exactly match one of the provided string patterns. This may be used with binary or string samples. - "end" : check that the contents end like the provided string patterns. This may be used with binary or string samples. - "reg" : match the contents against a list of regular expressions. This may be used with binary or string samples. For example, to quickly detect the presence of cookie "JSESSIONID" in an HTTP request, it is possible to do : acl jsess_present cook(JSESSIONID) -m found In order to apply a regular expression on the 500 first bytes of data in the buffer, one would use the following acl : acl script_tag payload(0,500) -m reg -i <script> The "-f" flag is special as it loads all of the lines it finds in the file specified in argument and loads all of them before continuing. It is even possible to pass multiple "-f" arguments if the patterns are to be loaded from multiple files. Empty lines as well as lines beginning with a sharp ('#') will be ignored. All leading spaces and tabs will be stripped. If it is absolutely needed to insert a valid pattern beginning with a sharp, just prefix it with a space so that it is not taken for a comment. Depending on the data type and match method, haproxy may load the lines into a binary tree, allowing very fast lookups. This is true for IPv4 and exact string matching. In this case, duplicates will automatically be removed. Also, note that the "-i" flag applies to subsequent entries and not to entries loaded from files preceding it. For instance : acl valid-ua hdr(user-agent) -f exact-ua.lst -i -f generic-ua.lst test In this example, each line of "exact-ua.lst" will be exactly matched against the "user-agent" header of the request. Then each line of "generic-ua" will be case-insensitively matched. Then the word "test" will be insensitively matched too. Note that right now it is difficult for the ACL parsers to report errors, so if a file is unreadable or unparsable, the most you'll get is a parse error in the ACL. Thus, file-based ACLs should only be produced by reliable processes. Supported types of values are : - integers or integer ranges - strings - regular expressions - IP addresses and networks
7.1. Matching integers
Matching integers is special in that ranges and operators are permitted. Note that integer matching only applies to positive values. A range is a value expressed with a lower and an upper bound separated with a colon, both of which may be omitted. For instance, "1024:65535" is a valid range to represent a range of unprivileged ports, and "1024:" would also work. "0:1023" is a valid representation of privileged ports, and ":1023" would also work. As a special case, some ACL functions support decimal numbers which are in fact two integers separated by a dot. This is used with some version checks for instance. All integer properties apply to those decimal numbers, including ranges and operators. For an easier usage, comparison operators are also supported. Note that using operators with ranges does not make much sense and is strongly discouraged. Similarly, it does not make much sense to perform order comparisons with a set of values. Available operators for integer matching are : eq : true if the tested value equals at least one value ge : true if the tested value is greater than or equal to at least one value gt : true if the tested value is greater than at least one value le : true if the tested value is less than or equal to at least one value lt : true if the tested value is less than at least one value For instance, the following ACL matches any negative Content-Length header : acl negative-length hdr_val(content-length) lt 0 This one matches SSL versions between 3.0 and 3.1 (inclusive) : acl sslv3 req_ssl_ver 3:3.1
7.2. Matching strings
String matching applies to verbatim strings as they are passed, with the
exception of the backslash ("\") which makes it possible to escape some
characters such as the space. If the "-i" flag is passed before the first
string, then the matching will be performed ignoring the case. In order
to match the string "-i", either set it second, or pass the "--" flag
before the first string. Same applies of course to match the string "--".7.3. Matching regular expressions (regexes)
Just like with string matching, regex matching applies to verbatim strings as
they are passed, with the exception of the backslash ("\") which makes it
possible to escape some characters such as the space. If the "-i" flag is
passed before the first regex, then the matching will be performed ignoring
the case. In order to match the string "-i", either set it second, or pass
the "--" flag before the first string. Same principle applies of course to
match the string "--".7.4. Matching IPv4 and IPv6 addresses
IPv4 addresses values can be specified either as plain addresses or with a
netmask appended, in which case the IPv4 address matches whenever it is
within the network. Plain addresses may also be replaced with a resolvable
host name, but this practice is generally discouraged as it makes it more
difficult to read and debug configurations. If hostnames are used, you should
at least ensure that they are present in /etc/hosts so that the configuration
does not depend on any random DNS match at the moment the configuration is
parsed.
IPv6 may be entered in their usual form, with or without a netmask appended.
Only bit counts are accepted for IPv6 netmasks. In order to avoid any risk of
trouble with randomly resolved IP addresses, host names are never allowed in
IPv6 patterns.
HAProxy is also able to match IPv4 addresses with IPv6 addresses in the
following situations :
- tested address is IPv4, pattern address is IPv4, the match applies
in IPv4 using the supplied mask if any.
- tested address is IPv6, pattern address is IPv6, the match applies
in IPv6 using the supplied mask if any.
- tested address is IPv6, pattern address is IPv4, the match applies in IPv4
using the pattern's mask if the IPv6 address matches with 2002:IPV4::,
::IPV4 or ::ffff:IPV4, otherwise it fails.
- tested address is IPv4, pattern address is IPv6, the IPv4 address is first
converted to IPv6 by prefixing ::ffff: in front of it, then the match is
applied in IPv6 using the supplied IPv6 mask.7.5. Available matching criteria
A number of predefined criteria may be used to form ACL expressions. The ones that are ACL-specific are detailed here. In addition to these ones, all sample fetch methods described in section 7.8 may be used. However, with these last ones, no default pattern matching method is defined, so it is mandatory to pass "-m" followed by a method. When a same keyword exists in both forms, the ACL compatible form prevails.
7.5.1. Matching at Layer 4 and below
A first set of criteria applies to information which does not require any analysis of the request or response contents. Those generally include TCP/IP addresses and ports, as well as internal values independent on the stream.
This one never matches. All values and flags are ignored. It may be used as a temporary replacement for another one when adjusting configurations.
This one always matches. All values and flags are ignored. It may be used as a temporary replacement for another one when adjusting configurations.
Returns the total number of queued connections of the designated backend divided by the number of active servers. This is very similar to "queue" except that the size of the farm is considered, in order to give a more accurate measurement of the time it may take for a new connection to be processed. The main usage is to return a sorry page to new users when it becomes certain they will get a degraded service. Note that in the event there would not be any active server anymore, we would consider twice the number of queued connections as the measured value. This is a fair estimate, as we expect one server to get back soon anyway, but we still prefer to send new traffic to another backend if in better shape. See also the "queue", "be_conn", and "be_sess_rate" criteria.
Applies to the number of currently established connections on the backend, possibly including the connection being evaluated. If no backend name is specified, the current one is used. But it is also possible to check another backend. It can be used to use a specific farm when the nominal one is full. See also the "fe_conn", "queue" and "be_sess_rate" criteria.
Applies to the backend's id. Can be used in frontends to check from which backend it was called.
Returns true when the sessions creation rate on the backend matches the specified values or ranges, in number of new sessions per second. This is used to switch to an alternate backend when an expensive or fragile one reaches too high a session rate, or to limit abuse of service (eg. prevent sucking of an online dictionary).
Example :
# Redirect to an error page if the dictionary is requested too often
backend dynamic
mode http
acl being_scanned be_sess_rate gt 100
redirect location /denied.html if being_scanned
Returns true when the sessions creation rate on the server matches the specified values or ranges, in number of new sessions per second. This is used to switch to an alternate backend when an expensive or fragile one reaches too high a session rate, or to limit abuse of service (eg. prevent latent requests from overloading servers).
Example :
# Redirect to a separate back
acl srv1_full srv_sess_rate(be1/srv1) gt 50
acl srv2_full srv_sess_rate(be1/srv2) gt 50
use_backend be2 if srv1_full or srv2_full
The basic idea here is to be able to measure the number of connection "slots" still available (connection + queue), so that anything beyond that (intended usage; see "use_backend" keyword) can be redirected to a different backend. 'connslots' = number of available server connection slots, + number of available server queue slots. Note that while "fe_conn" may be used, "connslots" comes in especially useful when you have a case of traffic going to one single ip, splitting into multiple backends (perhaps using acls to do name-based load balancing) and you want to be able to differentiate between different backends, and their available "connslots". Also, whereas "nbsrv" only measures servers that are actually *down*, this acl is more fine-grained and looks into the number of available connection slots as well. See also "queue" and "avg_queue". OTHER CAVEATS AND NOTES: at this point in time, the code does not take care of dynamic connections. Also, if any of the server maxconn, or maxqueue is 0, then this acl clearly does not make sense, in which case the value returned will be -1.
Applies to the local IPv4 or IPv6 address the client connected to. It can be used to switch to a different backend for some alternative addresses.
Applies to the number of currently established connections on the same socket including the one being evaluated. It can be used to either return a sorry page before hard-blocking, or to use a specific backend to drain new requests when the socket is considered saturated. This offers the ability to assign different limits to different listening ports or addresses. See also the "fe_conn" and "be_conn" criteria.
Applies to the local port the client connected to. It can be used to switch to a different backend for some alternative ports.
Applies to the number of currently established connections on the frontend, possibly including the connection being evaluated. If no frontend name is specified, the current one is used. But it is also possible to check another frontend. It can be used to either return a sorry page before hard-blocking, or to use a specific backend to drain new requests when the farm is considered saturated. See also the "dst_conn", "be_conn" and "fe_sess_rate" criteria.
Applies to the frontend's id. Can be used in backends to check from which frontend it was called.
Returns true when the session creation rate on the current or the named frontend matches the specified values or ranges, expressed in new sessions per second. This is used to limit the connection rate to acceptable ranges in order to prevent abuse of service at the earliest moment. This can be combined with layer 4 ACLs in order to force the clients to wait a bit for the rate to go down below the limit.
Example :
# This frontend limits incoming mails to 10/s with a max of 100
# concurrent connections. We accept any connection below 10/s, and
# force excess clients to wait for 100 ms. Since clients are limited to
# 100 max, there cannot be more than 10 incoming mails per second.
frontend mail
bind :25
mode tcp
maxconn 100
acl too_fast fe_sess_rate ge 10
tcp-request inspect-delay 100ms
tcp-request content accept if ! too_fast
tcp-request content accept if WAIT_END
Returns true when the number of usable servers of either the current backend or the named backend matches the values or ranges specified. This is used to switch to an alternate backend when the number of servers is too low to to handle some load. It is useful to report a failure when combined with "monitor fail".
Returns the total number of queued connections of the designated backend, including all the connections in server queues. If no backend name is specified, the current one is used, but it is also possible to check another one. This can be used to take actions when queuing goes above a known level, generally indicating a surge of traffic or a massive slowdown on the servers. One possible action could be to reject new users but still accept old ones. See also the "avg_queue", "be_conn", and "be_sess_rate" criteria.
Returns the average client-to-server bytes rate from the currently tracked counters, measured in amount of bytes over the period configured in the table. See also src_bytes_in_rate.
Returns the average server-to-client bytes rate from the currently tracked counters, measured in amount of bytes over the period configured in the table. See also src_bytes_out_rate.
Clears the first General Purpose Counter associated to the currently tracked
counters, and returns its previous value. Before the first invocation, the
stored value is zero, so first invocation will always return zero. This is
typically used as a second ACL in an expression in order to mark a connection
when a first ACL was verified :
# block if 5 consecutive requests continue to come faster than 10 sess
# per second, and reset the counter as soon as the traffic slows down.
acl abuse sc1_http_req_rate gt 10
acl kill sc1_inc_gpc0 gt 5
acl save sc1_clr_gpc0 ge 0
tcp-request connection accept if !abuse save
tcp-request connection reject if abuse killReturns the cumulated number of incoming connections from currently tracked counters. See also src_conn_cnt.
Returns the current amount of concurrent connections tracking the same tracked counters. This number is automatically incremented when tracking begins and decremented when tracking stops. See also src_conn_cur.
Returns the average connection rate from the currently tracked counters, measured in amount of connections over the period configured in the table. See also src_conn_rate.
Returns the value of the first General Purpose Counter associated to the currently tracked counters. See also src_get_gpc0 and sc1/sc2_inc_gpc0.
Returns the cumulated number of HTTP errors from the currently tracked counters. This includes the both request errors and 4xx error responses. See also src_http_err_cnt.
Returns the average rate of HTTP errors from the currently tracked counters, measured in amount of errors over the period configured in the table. This includes the both request errors and 4xx error responses. See also src_http_err_rate.
Returns the cumulated number of HTTP requests from the currently tracked counters. This includes every started request, valid or not. See also src_http_req_cnt.
Returns the average rate of HTTP requests from the currently tracked counters, measured in amount of requests over the period configured in the table. This includes every started request, valid or not. See also src_http_req_rate.
Increments the first General Purpose Counter associated to the currently
tracked counters, and returns its new value. Before the first invocation,
the stored value is zero, so first invocation will increase it to 1 and will
return 1. This is typically used as a second ACL in an expression in order
to mark a connection when a first ACL was verified :
acl abuse sc1_http_req_rate gt 10
acl kill sc1_inc_gpc0 gt 0
tcp-request connection reject if abuse killReturns the amount of client-to-server data from the currently tracked counters, measured in kilobytes over the period configured in the table. The test is currently performed on 32-bit integers, which limits values to 4 terabytes. See also src_kbytes_in.
Returns the amount of server-to-client data from the currently tracked counters, measured in kilobytes over the period configured in the table. The test is currently performed on 32-bit integers, which limits values to 4 terabytes. See also src_kbytes_out.
Returns the cumulated number of incoming connections that were transformed into sessions, which means that they were accepted by a "tcp-request connection" rule, from the currently tracked counters. A backend may count more sessions than connections because each connection could result in many backend sessions if some HTTP keep-alive is performed over the connection with the client. See also src_sess_cnt.
Returns the average session rate from the currently tracked counters, measured in amount of sessions over the period configured in the table. A session is a connection that got past the early "tcp-request connection" rules. A backend may count more sessions than connections because each connection could result in many backend sessions if some HTTP keep-alive is performed over the connection with the client. See also src_sess_rate.
Returns the current amount of concurrent connections tracking the same tracked counters. This number is automatically incremented when tracking begins and decremented when tracking stops. It differs from sc1_conn_cur in that it does not rely on any stored information but on the table's reference count (the "use" value which is returned by "show table" on the CLI). This may sometimes be more suited for layer7 tracking.
Applies to the socket's id. Useful in frontends with many bind keywords.
Applies to the client's IPv4 or IPv6 address. It is usually used to limit access to certain resources such as statistics. Note that it is the TCP-level source address which is used, and not the address of a client behind a proxy.
Returns the average bytes rate from the connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table, measured in amount of bytes over the period configured in the table. If the address is not found, zero is returned. See also sc1/sc2_bytes_in_rate.
Returns the average bytes rate to the connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table, measured in amount of bytes over the period configured in the table. If the address is not found, zero is returned. See also sc1/sc2_bytes_out_rate.
Clears the first General Purpose Counter associated to the connection's
source IPv4 address in the current proxy's stick-table or in the designated
stick-table, and returns its previous value. If the address is not found, an
entry is created and 0 is returned. This is typically used as a second ACL in
an expression in order to mark a connection when a first ACL was verified :
# block if 5 consecutive requests continue to come faster than 10 sess
# per second, and reset the counter as soon as the traffic slows down.
acl abuse src_http_req_rate gt 10
acl kill src_inc_gpc0 gt 5
acl save src_clr_gpc0 ge 0
tcp-request connection accept if !abuse save
tcp-request connection reject if abuse killReturns the cumulated number of connections initiated from the current connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table. If the address is not found, zero is returned. See also sc1/sc2_conn_cnt.
Returns the current amount of concurrent connections initiated from the current connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table. If the address is not found, zero is returned. See also sc1/sc2_conn_cur.
Returns the average connection rate from the connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table, measured in amount of connections over the period configured in the table. If the address is not found, zero is returned. See also sc1/sc2_conn_rate.
Returns the value of the first General Purpose Counter associated to the connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table. If the address is not found, zero is returned. See also sc1/sc2_get_gpc0 and src_inc_gpc0.
Returns the cumulated number of HTTP errors from the current connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table. This includes the both request errors and 4xx error responses. If the address is not found, zero is returned. See also sc1/sc2_http_err_cnt.
Returns the average rate of HTTP errors from the current connection's source IPv4 address in the current proxy's stick-table or in the designated stick- table, measured in amount of errors over the period configured in the table. This includes the both request errors and 4xx error responses. If the address is not found, zero is returned. See also sc1/sc2_http_err_rate.
Returns the cumulated number of HTTP requests from the current connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table. This includes every started request, valid or not. If the address is not found, zero is returned. See also sc1/sc2_http_req_cnt.
Returns the average rate of HTTP requests from the current connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table, measured in amount of requests over the period configured in the table. This includes every started request, valid or not. If the address is not found, zero is returned. See also sc1/sc2_http_req_rate.
Increments the first General Purpose Counter associated to the connection's
source IPv4 address in the current proxy's stick-table or in the designated
stick-table, and returns its new value. If the address is not found, an entry
is created and 1 is returned. This is typically used as a second ACL in an
expression in order to mark a connection when a first ACL was verified :
acl abuse src_http_req_rate gt 10
acl kill src_inc_gpc0 gt 0
tcp-request connection reject if abuse killReturns the amount of data received from the connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table, measured in kilobytes over the period configured in the table. If the address is not found, zero is returned. The test is currently performed on 32-bit integers, which limits values to 4 terabytes. See also sc1/sc2_kbytes_in.
Returns the amount of data sent to the connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table, measured in kilobytes over the period configured in the table. If the address is not found, zero is returned. The test is currently performed on 32-bit integers, which limits values to 4 terabytes. See also sc1/sc2_kbytes_out.
Applies to the client's TCP source port. This has a very limited usage.
Returns the cumulated number of connections initiated from the current connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table, that were transformed into sessions, which means that they were accepted by "tcp-request" rules. If the address is not found, zero is returned. See also sc1/sc2_sess_cnt.
Returns the average session rate from the connection's source IPv4 address in the current proxy's stick-table or in the designated stick-table, measured in amount of sessions over the period configured in the table. A session is a connection that got past the early "tcp-request" rules. If the address is not found, zero is returned. See also sc1/sc2_sess_rate.
Creates or updates the entry associated to the source IPv4 address in the current proxy's stick-table or in the designated stick-table. This table must be configured to store the "conn_cnt" data type, otherwise the match will be ignored. The current count is incremented by one, and the expiration timer refreshed. The updated count is returned, so this match can't return zero. This is used to reject service abusers based on their source address. Note: it is recommended to use the more complete "track-counters" instead.
Example :
# This frontend limits incoming SSH connections to 3 per 10 second for
# each source address, and rejects excess connections until a 10 second
# silence is observed. At most 20 addresses are tracked.
listen ssh
bind :22
mode tcp
maxconn 100
stick-table type ip size 20 expire 10s store conn_cnt
tcp-request content reject if { src_update_count gt 3 }
server local 127.0.0.1:22
Applies to the number of currently established connections on the server, possibly including the connection being evaluated. It can be used to use a specific farm when one server is full. See also the "fe_conn", "be_conn" and "queue" criteria.
Applies to the server's id. Can be used in frontends or backends.
Returns true when the designated server is UP, and false when it is either DOWN or in maintenance mode. If <backend> is omitted, then the server is looked up in the current backend. The function takes no arguments since it is used as a boolean. It is mainly used to take action based on an external status reported via a health check (eg: a geographical site's availability). Another possible use which is more of a hack consists in using dummy servers as boolean variables that can be enabled or disabled from the CLI, so that rules depending on those ACLs can be tweaked in realtime.
Returns the total number of available entries in the current proxy's stick-table or in the designated stick-table. See also table_cnt.
Returns the total number of entries currently in use in the current proxy's stick-table or in the designated stick-table. See also src_conn_cnt and table_avl for other entry counting methods.
7.5.2. Matching contents at Layer 4 (also called Layer 6)
A second set of criteria depends on data found in buffers, but which can change during analysis. This requires that some data has been buffered, for instance through TCP request content inspection. Please see the "tcp-request content" keyword for more detailed information on the subject.
Returns true when data in the response buffer looks like a complete SSL (v3 or superior) hello message and handshake type is equal to <integer>. This test was designed to be used with TCP response content inspection: a SSL session ID may be fetched. Note that this only applies to raw contents found in the response buffer and not to contents deciphered via an SSL data layer, so this will not work with "server" lines having the "ssl" option.
Returns true when the length of the data in the request buffer matches the specified range. It is important to understand that this test does not return false as long as the buffer is changing. This means that a check with equality to zero will almost always immediately match at the beginning of the session, while a test for more data will wait for that data to come in and return false only when haproxy is certain that no more data will come in. This test was designed to be used with TCP request content inspection.
Returns true when data in the request buffer look like HTTP and correctly parses as such. It is the same parser as the common HTTP request parser which is used so there should be no surprises. This test can be used for instance to direct HTTP traffic to a given port and HTTPS traffic to another one using TCP request content inspection rules.
Returns true when data in the request buffer look like the RDP protocol, and a cookie is present and equal to <string>. By default, any cookie name is checked, but a specific cookie name can be specified in parenthesis. The parser only checks for the first cookie, as illustrated in the RDP protocol specification. The cookie name is case insensitive. This ACL can be useful with the "MSTS" cookie, as it can contain the user name of the client connecting to the server if properly configured on the client. This can be used to restrict access to certain servers to certain users.
Returns true when the data in the request buffer look like the RDP protocol and the number of RDP cookies matches the specified range (typically zero or one). Optionally a specific cookie name can be checked. This is a simple way of detecting the RDP protocol, as clients generally send the MSTS or MSTSHASH cookies.
Returns true when data in the request buffer looks like a complete SSL (v3 or superior) hello message and handshake type is equal to <integer>. This test was designed to be used with TCP request content inspection: an SSL session ID may be fetched. Note that this only applies to raw contents found in the request buffer and not to contents deciphered via an SSL data layer, so this will not work with "bind" lines having the "ssl" option.
Returns true when data in the request buffer looks like a complete SSL (v3 or superior) client hello message with a Server Name Indication TLS extension (SNI) matching <string>. SNI normally contains the name of the host the client tries to connect to (for recent browsers). SNI is useful for allowing or denying access to certain hosts when SSL/TLS is used by the client. This test was designed to be used with TCP request content inspection. If content switching is needed, it is recommended to first wait for a complete client hello (type 1), like in the example below. Note that this only applies to raw contents found in the request buffer and not to contents deciphered via an SSL transport layer, so this will not work with "bind" lines having the "ssl" option. See also "ssl_sni" below.
Examples :
# Wait for a client hello for at most 5 seconds
tcp-request inspect-delay 5s
tcp-request content accept if { req_ssl_hello_type 1 }
use_backend bk_allow if { req_ssl_sni -f allowed_sites }
default_backend bk_sorry_page
Returns true when data in the request buffer look like SSL, with a protocol version matching the specified range. Both SSLv2 hello messages and SSLv3 messages are supported. The test tries to be strict enough to avoid being easily fooled. In particular, it waits for as many bytes as announced in the message header if this header looks valid (bound to the buffer size). Note that TLSv1 is announced as SSL version 3.1. This test was designed to be used with TCP request content inspection. Note that this only applies to raw contents found in the request buffer and not to contents deciphered via an SSL transport layer, so this will not work with "bind" lines having the "ssl" option.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the ID of the first error detected during verification of the client certificate at depth > 0 matches the specified value (check man verify for possible values). Note that error zero means no error was encountered during this verification process.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the depth in the CA chain of the first error detected during the verification of the client certificate matches the specified value. When no error is found, depth 0 is returned.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the ID of the first error detected during verification at depth==0 matches the specified value (check man verify for possible values). Note that error zero means no error was encountered during this verification process.
ssl_c_i_dn(entry[,occ]) <string> If no entry specified, returns true when the incoming connection was made over an SSL/TLS transport layer, and the full distinguished name of the issuer of the certificate presented by the client matches the specified string. Otherwise returns true if the value of the first given entry from the beginning of the DN matches the specified string. If a positive/negative occurrence number is specified as the optional second argument, it returns true if the value of the nth given entry value from the beginning/end of the DN matches the specified string.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the name of the algorithm used to generate the key of the certificate presented by the client matches the string.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the end date of the certificate presented by the client matches the string formatted as YYMMDDhhmmss[Z].
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the start date of the certificate presented by the client matches the string formatted as YYMMDDhhmmss[Z].
ssl_c_s_dn(entry[,occ]) <string> If no entry specified, returns true when the incoming connection was made over an SSL/TLS transport layer, and the full distinguished name of the subject of the certificate presented by the client matches the specified string. Otherwise returns true if the value of the first given entry from the beginning of the DN matches the specified string. If a positive/negative occurrence number is specified as the optional second argument, it returns true if the value of the nth given entry value from the beginning/end of the DN matches the specified string.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the serial of the certificate presented by the client matches the value written in hexa.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the name of the algorithm used to sign the certificate presented by the client matches the string.
Returns true if current SSL session uses a client certificate even if current connection uses SSL session resumption. See also "ssl_fc_has_crt".
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the verify result matches the specified value (check man verify for possible values). Zero indicates no error was detected.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the version of the certificate presented by the client matches the value.
ssl_f_i_dn(entry[,occ]) <string> If no entry specified, returns true when the incoming connection was made over an SSL/TLS transport layer, and the full distinguished name of the issuer of the certificate presented by the frontend matches the specified string. Otherwise returns true if the value of the first given entry from the beginning of the DN matches the specified string. If a positive/negative occurrence number is specified as the optional second argument, it returns true if the value of the nth given entry value from the beginning/end of the DN matches the specified string.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the name of the algorithm used to generate the key of the certificate presented by the frontend matches the string.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the end date of the certificate presented by the frontend matches the string formatted as YYMMDDhhmmss[Z].
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the start date of the certificate presented by the frontend matches the string formatted as YYMMDDhhmmss[Z].
ssl_f_s_dn(entry[,occ]) <string> If no entry specified, returns true when the incoming connection was made over an SSL/TLS transport layer, and the full distinguished name of the subject of the certificate presented by the frontend matches the specified string. Otherwise returns true if the value of the first given entry from the beginning of the DN matches the specified string. If a positive/negative occurrence number is specified as the optional second argument, it returns true if the value of the nth given entry value from the beginning/end of the DN matches the specified string.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the serial of the certificate presented by the frontend matches the value written in hexa.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the name of the algorithm used to sign the certificate presented by the frontend matches the string.
Returns true when the incoming connection was made over an SSL/TLS transport layer, and the version of the certificate presented by the frontend matches the value.
Returns true when the front connection was made via an SSL/TLS transport layer and is locally deciphered. This means it has matched a socket declared with a "bind" line having the "ssl" option.
Returns true when the incoming connection was made over an SSL/TLS transport layer and the symmetric cipher key size supported in bits matches the value.
Returns true when the incoming connection was made over an SSL/TLS transport layer which deciphered it and found a Next Protocol Negociation TLS extension sent by the client, matching the specified string. This requires that the SSL library is build with support for TLS extensions enabled (check haproxy -vv). Note that the TLS ALPN extension is not advertised unless the "alpn" keyword on the "bind" line specifies a protocol list. Also, nothing forces the client to pick a protocol from this list, any other one may be requested. The TLS ALPN extension is meant to replace the TLS NPN extension.
returns true when the incoming connection was made over an ssl/tls transport layer and the name of the used cipher matches the string.
Returns true if a client certificate is present in an incoming connection over SSL/TLS transport layer. Useful if 'verify' statement is set to 'optional'. Note: on SSL session resumption with Session ID or TLS ticket, client certificate is not present in the current connection but may be retrieved from the cache or the ticket. So prefer "ssl_c_used" if you want to check if current SSL session uses a client certificate.
This is used to check for presence of a Server Name Indication TLS extension in an incoming connection was made over an SSL/TLS transport layer. Returns true when the incoming connection presents a TLS SNI field. This requires that the SSL library is build with support for TLS extensions enabled (check haproxy -vv).
Returns true when the incoming connection was made over an SSL/TLS transport layer which deciphered it and found a Next Protocol Negociation TLS extension sent by the client, matching the specified string. This requires that the SSL library is build with support for TLS extensions enabled (check haproxy -vv). Note that the TLS NPN extension is not advertised unless the "npn" keyword on the "bind" line specifies a protocol list. Also, nothing forces the client to pick a protocol from this list, any other one may be requested. Please note that the TLS NPN extension was replaced with ALPN.
Returns true when the incoming connection was made over an SSL/TLS transport layer and the name of the used protocol matches the string.
Returns true when the incoming connection was made over an SSL/TLS transport layer which deciphered it and found a Server Name Indication TLS extension sent by the client, matching the specified string. In HTTPS, the SNI field (when present) is equal to the requested host name. This match is different from "req_ssl_sni" above in that it applies to the connection being deciphered by haproxy and not to SSL contents being blindly forwarded. See also "ssl_fc_sni_end" and "ssl_fc_sni_req" below. This requires that the SSL library is build with support for TLS extensions enabled (check haproxy -vv).
Returns true when the incoming connection was made over an SSL/TLS transport layer which deciphered it and found a Server Name Indication TLS extension sent by the client, ending like the specified string. In HTTPS, the SNI field (when present) is equal to the requested host name. This match is different from "req_ssl_sni" above in that it applies to the connection being deciphered by haproxy and not to SSL contents being blindly forwarded. This requires that the SSL library is build with support for TLS extensions enabled (check haproxy -vv).
Returns true when the incoming connection was made over an SSL/TLS transport layer which deciphered it and found a Server Name Indication TLS extension sent by the client, matching the specified regex. In HTTPS, the SNI field (when present) is equal to the requested host name. This match is different from "req_ssl_sni" above in that it applies to the connection being deciphered by haproxy and not to SSL contents being blindly forwarded. This requires that the SSL library is build with support for TLS extensions enabled (check haproxy -vv).
Returns true when the incoming connection was made over an SSL/TLS transport layer and the symmetric cipher key size used in bits matches the value.
Waits for the end of the analysis period to return true. This may be used in conjunction with content analysis to avoid returning a wrong verdict early. It may also be used to delay some actions, such as a delayed reject for some special addresses. Since it either stops the rules evaluation or immediately returns true, it is recommended to use this acl as the last one in a rule. Please note that the default ACL "WAIT_END" is always usable without prior declaration. This test was designed to be used with TCP request content inspection.
Examples :
# delay every incoming request by 2 seconds
tcp-request inspect-delay 2s
tcp-request content accept if WAIT_END
# don't immediately tell bad guys they are rejected
tcp-request inspect-delay 10s
acl goodguys src 10.0.0.0/24
acl badguys src 10.0.1.0/24
tcp-request content accept if goodguys
tcp-request content reject if badguys WAIT_END
tcp-request content reject
7.5.3. Matching at Layer 7
A third set of criteria applies to information which can be found at the application layer (layer 7). Those require that a full HTTP request has been read, and are only evaluated then. They may require slightly more CPU resources than the layer 4 ones, but not much since the request and response are indexed.
Returns true when the concatenation of the first Host header and the path part of the request, which starts at the first slash and ends before the question mark, equals one of the strings. It may be used to match known files in virtual hosting environments, such as "www.example.com/favicon.ico". See also "path" and "uri".
Returns true when the base (see above) begins with one of the strings. This can be used to send certain directory names to alternative backends. See also "path_beg".
Returns true when one of the strings is found isolated or delimited with slashes in the base (see above). Probably of little use, see "url_dir" and "path_dir" instead.
Returns true when one of the strings is found isolated or delimited with dots in the base (see above). Probably of little use, see "path_dom" and "url_dom" instead.
Returns true when the base (see above) ends with one of the strings. This may be used to control file name extension, though "path_end" is cheaper.
Returns true when the base (see above) length matches the values or ranges specified. This may be used to detect abusive requests for instance.
Returns true when the base (see above) matches one of the regular expressions. It can be used any time, but it is important to remember that regex matching is slower than other methods. See also "path_reg", "url_reg" and all "base_" criteria.
Returns true when the base (see above) contains one of the strings. It can be used to detect particular patterns in paths, such as "../" for example. See also "base_dir".
All "cook*" matching criteria inspect all "Cookie" headers to find a cookie with the name between parenthesis. If multiple occurrences of the cookie are found in the request, they will all be evaluated. Spaces around the name and the value are ignored as requested by the Cookie specification (RFC6265). The cookie name is case-sensitive. Use the scook() variant for response cookies sent by the server. The "cook" criteria returns true if any of the request cookies <name> match any of the strings. This can be used to check exact for values. For instance, checking that the "profile" cookie is set to either "silver" or "gold" : cook(profile) silver gold
Returns true if any of the request cookies <name> begins with one of the strings. See "cook" for more information on cookie matching. Use the scook_beg() variant for response cookies sent by the server.
Returns true when the number of occurrences of the specified cookie matches the values or ranges specified. This is used to detect presence, absence or abuse of a specific cookie. See "cook" for more information on header matching. Use the scook_cnt() variant for response cookies sent by the server.
Returns true if any of the request cookies <name> contains one of the strings either isolated or delimited by slashes. This is used to perform filename or directory name matching, though it generally is of limited use with cookies. See "cook" for more information on cookie matching. Use the scook_dir() variant for response cookies sent by the server.
Returns true if any of the request cookies <name> contains one of the strings either isolated or delimited by dots. This is used to perform domain name matching. See "cook" for more information on cookie matching. Use the scook_dom() variant for response cookies sent by the server.
Returns true if any of the request cookies <name> ends with one of the strings. See "cook" for more information on cookie matching. Use the scook_end() variant for response cookies sent by the server.
Returns true if any of the request cookies <name> has a length which matches the values or ranges specified. This may be used to detect empty or too large cookie values. Note that an absent cookie does not match a zero-length test. See "cook" for more information on cookie matching. Use the scook_len() variant for response cookies sent by the server.
Returns true if any of the request cookies <name> matches any of the regular expressions. It can be used at any time, but it is important to remember that regex matching is slower than other methods. See also other "cook_" criteria, as well as "cook" for more information on cookie matching. Use the scook_reg() variant for response cookies sent by the server.
Returns true if any of the request cookies <name> contains at least one of the strings. See "cook" for more information on cookie matching. Use the scook_sub() variant for response cookies sent by the server.
Returns true if any of the request cookies <name> starts with a number which matches the values or ranges specified. This may be used to select a server based on application-specific cookies. Note that an absent cookie does not match any value. See "cook" for more information on cookie matching. Use the scook_val() variant for response cookies sent by the server.
Note: all the "hdr*" matching criteria either apply to all headers, or to a particular header whose name is passed between parenthesis and without any space. The header name is not case-sensitive. The header matching complies with RFC2616, and treats as separate headers all values delimited by commas. If an occurrence number is specified as the optional second argument, only this occurrence will be considered. Positive values indicate a position from the first occurrence, 1 being the first one. Negative values indicate positions relative to the last one, -1 being the last one. Use the shdr() variant for response headers sent by the server. The "hdr" criteria returns true if any of the headers matching the criteria match any of the strings. This can be used to check for exact values. For instance, checking that "connection: close" is set : hdr(Connection) -i close
Returns true when one of the headers begins with one of the strings. See "hdr" for more information on header matching. Use the shdr_beg() variant for response headers sent by the server.
Returns true when the number of occurrence of the specified header matches the values or ranges specified. It is important to remember that one header line may count as several headers if it has several values. This is used to detect presence, absence or abuse of a specific header, as well as to block request smuggling attacks by rejecting requests which contain more than one of certain headers. See "hdr" for more information on header matching. Use the shdr_cnt() variant for response headers sent by the server.
Returns true when one of the headers contains one of the strings either isolated or delimited by slashes. This is used to perform filename or directory name matching, and may be used with Referer. See "hdr" for more information on header matching. Use the shdr_dir() variant for response headers sent by the server.
Returns true when one of the headers contains one of the strings either isolated or delimited by dots. This is used to perform domain name matching, and may be used with the Host header. See "hdr" for more information on header matching. Use the shdr_dom() variant for response headers sent by the server.
Returns true when one of the headers ends with one of the strings. See "hdr" for more information on header matching. Use the shdr_end() variant for response headers sent by the server.
Returns true when one of the headers' values contains an IPv4 or IPv6 address matching <address>. This is mainly used with headers such as X-Forwarded-For or X-Client-IP. See "hdr" for more information on header matching. Use the shdr_ip() variant for response headers sent by the server.
Returns true when at least one of the headers has a length which matches the values or ranges specified. This may be used to detect empty or too large headers. See "hdr" for more information on header matching. Use the shdr_len() variant for response headers sent by the server.
Returns true it one of the headers matches one of the regular expressions. It can be used at any time, but it is important to remember that regex matching is slower than other methods. See also other "hdr_" criteria, as well as "hdr" for more information on header matching. Use the shdr_reg() variant for response headers sent by the server.
Returns true when one of the headers contains one of the strings. See "hdr" for more information on header matching. Use the shdr_sub() variant for response headers sent by the server.
Returns true when one of the headers starts with a number which matches the values or ranges specified. This may be used to limit content-length to acceptable values for example. See "hdr" for more information on header matching. Use the shdr_val() variant for response headers sent by the server.
Returns true when authentication data received from the client matches username & password stored on the userlist. It is also possible to use http_auth_group to check if the user is assigned to at least one of specified groups. Currently only http basic auth is supported.
Returns true when the request being processed is the first one of the connection. This can be used to add or remove headers that may be missing from some requests when a request is not the first one, or even to perform some specific ACL checks only on the first request.
Applies to the method in the HTTP request, eg: "GET". Some predefined ACL already check for most common methods.
Returns true when the path part of the request, which starts at the first slash and ends before the question mark, equals one of the strings. It may be used to match known files, such as /favicon.ico.
Returns true when the path begins with one of the strings. This can be used to send certain directory names to alternative backends.
Returns true when one of the strings is found isolated or delimited with slashes in the path. This is used to perform filename or directory name matching without the risk of wrong match due to colliding prefixes. See also "url_dir" and "path_sub".
Returns true when one of the strings is found isolated or delimited with dots in the path. This may be used to perform domain name matching in proxy requests. See also "path_sub" and "url_dom".
Returns true when the path ends with one of the strings. This may be used to control file name extension.
Returns true when the path length matches the values or ranges specified. This may be used to detect abusive requests for instance.
Returns true when the path matches one of the regular expressions. It can be used any time, but it is important to remember that regex matching is slower than other methods. See also "url_reg" and all "path_" criteria.
Returns true when the path contains one of the strings. It can be used to detect particular patterns in paths, such as "../" for example. See also "path_dir".
Returns true if the block of <length> bytes, starting at byte <offset> in the request or response buffer (depending on the rule) exactly matches one of the strings.
Returns true if the block whose size is specified at <offset1> for <length> bytes, and which starts at <offset2> if specified or just after the length in the request or response buffer (depending on the rule) exactly matches one of the strings. The <offset2> parameter also supports relative offsets if prepended with a '+' or '-' sign.
Applies to the version string in the HTTP request, eg: "1.0". Some predefined ACL already check for versions 1.0 and 1.1.
Applies to the HTTP status code in the HTTP response, eg: "302". It can be used to act on responses depending on status ranges, for instance, remove any Location header if the response is not a 3xx.
Applies to the whole URL passed in the request. The only real use is to match "*", for which there already is a predefined ACL. See also "base".
Returns true when the URL begins with one of the strings. This can be used to check whether a URL begins with a slash or with a protocol scheme. See also "base_beg".
Returns true when one of the strings is found isolated or delimited with slashes in the URL. This is used to perform filename or directory name matching without the risk of wrong match due to colliding prefixes. See also "path_dir" and "url_sub".
Returns true when one of the strings is found isolated or delimited with dots in the URL. This is used to perform domain name matching without the risk of wrong match due to colliding prefixes. See also "url_sub".
Returns true when the URL ends with one of the strings. It has very limited use. "path_end" should be used instead for filename matching.
Applies to the IPv4 or IPv6 address specified in the absolute URI in an HTTP request. It can be used to prevent access to certain resources such as local network. It is useful with option "http_proxy".
Returns true when the url length matches the values or ranges specified. This may be used to detect abusive requests for instance.
Applies to the port specified in the absolute URI in an HTTP request. It can be used to prevent access to certain resources. It is useful with option "http_proxy". Note that if the port is not specified in the request, port 80 is assumed.
Returns true when the URL matches one of the regular expressions. It can be used any time, but it is important to remember that regex matching is slower than other methods. See also "base_reg", "path_reg" and all "url_" criteria.
Returns true when the URL contains one of the strings. It can be used to detect particular patterns in query strings for example. See also "path_sub".
Note: all "urlp*" matching criteria apply to the first occurrence of the parameter <name> in the query string. The parameter name is case-sensitive. The "urlp" matching criteria returns true if the designated URL parameter matches any of the strings. This can be used to check for exact values.
Returns true when the URL parameter "<name>" begins with one of the strings. This can be used to check whether a URL begins with a slash or with a protocol scheme.
Returns true when the URL parameter "<name>" contains one of the strings either isolated or delimited with slashes. This is used to perform filename or directory name matching in a specific URL parameter without the risk of wrong match due to colliding prefixes. See also "path_dir" and "urlp_sub".
Returns true when one of the strings is found isolated or delimited with dots in the URL parameter "<name>". This is used to perform domain name matching in a specific URL parameter without the risk of wrong match due to colliding prefixes. See also "urlp_sub".
Returns true when the URL parameter "<name>" ends with one of the strings.
Returns true when the URL parameter "<name>" contains an IPv4 or IPv6 address which matches one of the specified addresses.
Returns true when the URL parameter "<name>" has a length matching the values or ranges specified. This is used to detect abusive requests for instance.
Returns true when the URL parameter "<name>" matches one of the regular expressions. It can be used any time, but it is important to remember that regex matching is slower than other methods. See also "path_reg" and all "urlp_" criteria.
Returns true when the URL parameter "<name>" contains one of the strings. It can be used to detect particular patterns in query strings for example. See also "path_sub" and other "urlp_" criteria.
Returns true when the URL parameter "<name>" starts with a number matching the values or ranges specified. Note that the absence of the parameter does not match anything. Integers are unsigned so it is not possible to match negative data.
7.6. Pre-defined ACLs
Some predefined ACLs are hard-coded so that they do not have to be declared in every frontend which needs them. They all have their names in upper case in order to avoid confusion. Their equivalence is provided below.
| ACL name | Equivalent to | Usage |
|---|---|---|
| FALSE | always_false | never match |
| HTTP | req_proto_http | match if protocol is valid HTTP |
| HTTP_1.0 | req_ver 1.0 | match HTTP version 1.0 |
| HTTP_1.1 | req_ver 1.1 | match HTTP version 1.1 |
| HTTP_CONTENT | hdr_val(content-length) gt 0 | match an existing content-length |
| HTTP_URL_ABS | url_reg ^[^/:]*:// | match absolute URL with scheme |
| HTTP_URL_SLASH | url_beg / | match URL beginning with "/" |
| HTTP_URL_STAR | url * | match URL equal to "*" |
| LOCALHOST | src 127.0.0.1/8 | match connection from local host |
| METH_CONNECT | method CONNECT | match HTTP CONNECT method |
| METH_GET | method GET HEAD | match HTTP GET or HEAD method |
| METH_HEAD | method HEAD | match HTTP HEAD method |
| METH_OPTIONS | method OPTIONS | match HTTP OPTIONS method |
| METH_POST | method POST | match HTTP POST method |
| METH_TRACE | method TRACE | match HTTP TRACE method |
| RDP_COOKIE | req_rdp_cookie_cnt gt 0 | match presence of an RDP cookie |
| REQ_CONTENT | req_len gt 0 | match data in the request buffer |
| TRUE | always_true | always match |
| WAIT_END | wait_end | wait for end of content analysis |
7.7. Using ACLs to form conditions
Some actions are only performed upon a valid condition. A condition is a
combination of ACLs with operators. 3 operators are supported :
- AND (implicit)
- OR (explicit with the "or" keyword or the "||" operator)
- Negation with the exclamation mark ("!")
A condition is formed as a disjunctive form:
[!]acl1 [!]acl2 ... [!]acln { or [!]acl1 [!]acl2 ... [!]acln } ...
Such conditions are generally used after an "if" or "unless" statement,
indicating when the condition will trigger the action.
For instance, to block HTTP requests to the "*" URL with methods other than
"OPTIONS", as well as POST requests without content-length, and GET or HEAD
requests with a content-length greater than 0, and finally every request which
is not either GET/HEAD/POST/OPTIONS !
acl missing_cl hdr_cnt(Content-length) eq 0
block if HTTP_URL_STAR !METH_OPTIONS || METH_POST missing_cl
block if METH_GET HTTP_CONTENT
block unless METH_GET or METH_POST or METH_OPTIONS
To select a different backend for requests to static contents on the "www" site
and to every request on the "img", "video", "download" and "ftp" hosts :
acl url_static path_beg /static /images /img /css
acl url_static path_end .gif .png .jpg .css .js
acl host_www hdr_beg(host) -i www
acl host_static hdr_beg(host) -i img. video. download. ftp.
# now use backend "static" for all static-only hosts, and for static urls
# of host "www". Use backend "www" for the rest.
use_backend static if host_static or host_www url_static
use_backend www if host_www
It is also possible to form rules using "anonymous ACLs". Those are unnamed ACL
expressions that are built on the fly without needing to be declared. They must
be enclosed between braces, with a space before and after each brace (because
Example :
The following rule :
acl missing_cl hdr_cnt(Content-length) eq 0
block if METH_POST missing_cl
Can also be written that way :
block if METH_POST { hdr_cnt(Content-length) eq 0 }
It is generally not recommended to use this construct because it's a lot easier
to leave errors in the configuration when written that way. However, for very
simple rules matching only one source IP address for instance, it can make more
sense to use them than to declare ACLs with random names. Another example of
good use is the following :
With named ACLs :
acl site_dead nbsrv(dynamic) lt 2
acl site_dead nbsrv(static) lt 2
monitor fail if site_dead
With anonymous ACLs :
monitor fail if { nbsrv(dynamic) lt 2 } || { nbsrv(static) lt 2 }
See section 4.2 for detailed help on the "block" and "use_backend" keywords.7.8. Pattern extraction
The stickiness features relies on pattern extraction in the request and
response. Sometimes the data needs to be converted first before being stored,
for instance converted from ASCII to IP or upper case to lower case.
All these operations of data extraction and conversion are defined as
"pattern extraction rules". A pattern rule always has the same format. It
begins with a single pattern fetch word, potentially followed by a list of
arguments within parenthesis then an optional list of transformations. As
much as possible, the pattern fetch functions use the same name as their
equivalent used in ACLs.
The list of currently supported pattern fetch functions is the following :
always_false
Always returns the boolean "false" value.
always_true
Always returns the boolean "true" value.
avg_queue([<backend>])
Returns the total number of queued connections of the designated
backend divided by the number of active servers. The current
backend is used if no backend is specified. This is very similar
to "queue" except that the size of the farm is considered, in
order to give a more accurate measurement of the time it may
take for a new connection to be processed. The main usage is
with ACL to return a sorry page to new users when it becomes
certain they will get a degraded service, or to pass to the
backend servers in a header so that they decide to work in
degraded mode or to disable some functions to speed up the
processing a bit. Note that in the event there would not be
any active server anymore, we would consider twice the number
of queued connections as the measured value. This is a fair
estimate, as we expect one server to get back soon anyway, but
we still prefer to send new traffic to another backend if in
better shape. See also the "queue", "be_conn", and
"be_sess_rate" sample fetches.
base This returns the concatenation of the first Host header and the
path part of the request, which starts at the first slash and
ends before the question mark. It can be useful in virtual
hosted environments to detect URL abuses as well as to improve
shared caches efficiency. Using this with a limited size stick
table also allows one to collect statistics about most commonly
requested objects by host/path.
base32 This returns a 32-bit hash of the value returned by the "base"
fetch method above. This is useful to track per-URL activity on
high traffic sites without having to store all URLs. Instead a
shorter hash is stored, saving a lot of memory. The output type
is an unsigned integer.
base32+src This returns the concatenation of the base32 fetch above and the
src fetch below. The resulting type is of type binary, with a
size of 8 or 20 bytes depending on the source address family.
This can be used to track per-IP, per-URL counters.
be_conn([<backend>])
Returns the number of currently established connections on the
the backend, possibly including the connection being evaluated.
If no backend name is specified, the current one is used. But it
is also possible to check another backend. It can be used to use
a specific farm when the nominal one is full. See also the
"fe_conn", "queue" and "be_sess_rate" criteria.
be_id Returns an integer containing the current backend's id.
be_sess_rate([<backend>])
Returns an integer value corresponding to the sessions creation
rate on the backend, in number of new sessions per second. This
is used with ACLs to switch to an alternate backend when an
expensive or fragile one reaches too high a session rate, or to
limit abuse of service (eg. prevent sucking of an online
dictionary). It can also be useful to add this element to logs
using a log-format directive.
connslots([<backend>])
Returns an integer value corresponding to the number of
connection slots still available in the backend, by totalizing
the maximum amount of connections on all servers and the maximum
queue size. This is only used with ACLs. See the ACL "connslots"
keyword description for more information on possible caveats.
cook([<name>])
This is an alias for "req.cook".
cookie([<name>])
This extracts the last occurrence of the cookie name <name> on a
"Cookie" header line from the request, or a "Set-Cookie" header
from the response, and returns its value as a string. A typical
use is to get multiple clients sharing a same profile use the
same server. This can be similar to what "appsession" does with
the "request-learn" statement, but with support for multi-peer
synchronization and state keeping across restarts. If no name is
specified, the first cookie value is returned.See also : "appsession"
cook_cnt([<name>])
This is an alias for "req.cook_cnt".
cook_val([<name>])
This is an alias for "req.cook_val".
dst This is the destination IPv4 address of the session on the
client side, which is the address the client connected to.
It can be useful when running in transparent mode. It is of
type IPv4 and works on both IPv4 and IPv6 tables.
On IPv6 tables, IPv4 address is mapped to its IPv6 equivalent,
according to RFC 4291.
dst_conn
Returns an integer value corresponding to the number of
currently established connections on the same socket including
the one being evaluated. It is normally used with ACLs but can
as well be used to pass the information to servers in an HTTP
header or in logs. See also "fe_conn" and "dst_conn".
dst_port This is the destination TCP port of the session on the client
side, which is the port the client connected to. This might be
used when running in transparent mode or when assigning dynamic
ports to some clients for a whole application session. It is of
type integer and only works with such tables.
fe_conn([<frontend>])
Returns the number of currently established connections on the
the frontend, possibly including the connection being evaluated.
If no frontend name is specified, the current one is used. But
it is also possible to check another frontend. It can be used to
return a sorry page before hard-blocking, or to use a specific
backend to drain new requests when the farm is considered full.
This is mostly used with ACLs but can also be used to pass some
statistics to servers in HTTP headers. See also the "dst_conn",
"be_conn", "fe_sess_rate" criteria.
fe_id Returns an integer containing the current frontend's id.
fe_sess_rate([<frontend>])
Returns an integer value corresponding to the sessions creation
rate on the frontend, in number of new sessions per second. This
is used with ACLs to limit the incoming session rate to an
acceptable range in order to prevent abuse of service at the
earliest moment. It can also be useful to add this element to
logs using a log-format directive.
hdr(<name>[,<occ>])
This is an alias for "req.hdr" or "res.hdr" depending whether it
is used on the request path or the response path. Since it is
ambiguous, it is recommended not to use this form.
hdr_cnt([<name>])
This is an alias for "req.hdr_cnt".
hdr_ip([<name>[,<occ>]])
This is an alias for "req.hdr_ip".
hdr_val([<name>[,<occ>]])
This is an alias for "req.hdr_val".
http_auth(<userlist>)
http_auth_group(<userlist>)
Returns a boolean indicating whether the authentication data
received from the client match a username & password stored in
the specified userlist. These fetch functions are not really
useful outside of ACLs.
http_first_req
Returns true when the request being processed is the first one
of the connection. This can be used to add or remove headers
that may be missing from some requests when a request is not the
first one, or to help grouping requests in the logs.
method
Returns an integer value corresponding to the to the method in
the HTTP request. For example, "GET" equals 1 (check sources to
establish the matching). Value 9 means "other method" and may be
converted to a string extracted from the stream. This should not
be used directly, this is only meant to be used from ACLs.
nbsrv([<backend>])
Returns an integer value corresponding to the number of usable
servers of either the current backend or the named backend. This
is mostly used with ACLs but can also be useful when added to
logs.
path This extracts the request's URL path (without the host part). A
typical use is with prefetch-capable caches, and with portals
which need to aggregate multiple information from databases and
keep them in caches. Note that with outgoing caches, it would be
wiser to use "url" instead.
payload(<offset>,<length>)
This is an alias for "req.payload" when used in the context of a
request (eg: "stick on", "stick match"), and for "res.payload"
when used in the context of a response such as in
"stick store response".
payload_lv(<offset1>,<length>[,<offset2>])
This is an alias for "req.payload_lv" when used in the context
of a request (eg: "stick on" or "stick match"), and for
"res.payload_lv" when used in the context of a response such as
in "stick store response".
queue([<backend>])
Returns the total number of queued connections of the designated
backend, including all the connections in server queues. If no
backend name is specified, the current one is used, but it is
also possible to check another one. This is useful with ACLs
or to pass statistics to backend servers.
rdp_cookie(<name>)
This is an alias for "req.rdp_cookie".
rdp_cookie_cnt([name])
This is an alias for "req.rdp_cookie_cnt".
rep_ssl_hello_type
This is an alias for "res.ssl_hello_type".
req.cook([<name>])
This extracts the last occurrence of the cookie name <name> on a
"Cookie" header line from the request, and returns its value as
string. If no name is specified, the first cookie value is
returned.
req.cook_cnt([<name>])
Returns an integer value representing the number of occurrences of
the cookie <name> in the request, or all cookies if <name> is not
specified.
req.cook_val([<name>])
This extracts the last occurrence of the cookie name <name> on a
"Cookie" header line from the request, and converts its value to
an integer which is returned. If no name is specified, the first
cookie value is returned.
req.hdr(<name>[,<occ>])
This extracts the last occurrence of header <name> in an HTTP
request. Optionally, a specific occurrence might be specified as
a position number. Positive values indicate a position from the
first occurrence, with 1 being the first one. Negative values
indicate positions relative to the last one, with -1 being the
last one. A typical use is with the X-Forwarded-For header once
converted to IP, associated with an IP stick-table.
req.hdr_cnt([<name>])
Returns an integer value representing the number of occurrences
of request header field name <name>, or the total number of
header fields if <name> is not specified.
req.hdr_ip([<name>[,<occ>]])
This extracts the last occurrence of header <name> in an HTTP
request, converts it to an IPv4 or IPv6 address and returns this
address. Optionally, a specific occurrence might be specified as
a position number. Positive values indicate a position from the
first occurrence, with 1 being the first one. Negative values
indicate positions relative to the last one, with -1 being the
last one. A typical use is with the X-Forwarded-For header.
req.hdr_val([<name>[,<occ>]])
This extracts the last occurrence of header <name> in an HTTP
request, and converts it to an integer value. Optionally, a
specific occurrence might be specified as a position number.
Positive values indicate a position from the first occurrence,
with 1 being the first one. Negative values indicate positions
relative to the last one, with -1 being the last one. A typical
use is with the X-Forwarded-For header.
req.len Returns an integer value corresponding to the number of bytes
present in the request buffer. This is mostly used in ACL.
req.payload(<offset>,<length>)
This extracts a binary block of <length> bytes and starting at
bytes <offset> in the request buffer.
req.payload_lv(<offset1>,<length>[,<offset2>])
This extracts a binary block. In a first step the size of the
block is read from the request request buffer at <offset> bytes
and considered coded on <length> bytes. In a second step data of
the block are read from buffer at <offset2> bytes (by default
<lengthoffset> + <lengthsize>). If <offset2> is prefixed by '+'
or '-', it is relative to <lengthoffset> + <lengthsize> else it
is absolute. Ex: see SSL session id example in "stick table"
chapter.
req.proto_http
Returns true when data in the request buffer look like HTTP and
correctly parses as such. It is the same parser as the common
HTTP request parser which is used so there should be no
surprises. This test may be used to report the protocol in TCP
logs.
req.rdp_cookie(<name>)
This extracts the value of the rdp cookie <name> as a string
and uses this value to match. This enables implementation of
persistence based on the mstshash cookie. This is typically
done if there is no msts cookie present.
This differs from "balance rdp-cookie" in that any balancing
algorithm may be used and thus the distribution of clients
to backend servers is not linked to a hash of the RDP
cookie. It is envisaged that using a balancing algorithm
such as "balance roundrobin" or "balance leastconn" will
lead to a more even distribution of clients to backend
servers than the hash used by "balance rdp-cookie".
Example :
listen tse-farm
bind 0.0.0.0:3389
# wait up to 5s for an RDP cookie in the request
tcp-request inspect-delay 5s
tcp-request content accept if RDP_COOKIE
# apply RDP cookie persistence
persist rdp-cookie
# Persist based on the mstshash cookie
# This is only useful makes sense if
# balance rdp-cookie is not used
stick-table type string size 204800
stick on req.rdp_cookie(mstshash)
server srv1 1.1.1.1:3389
server srv1 1.1.1.2:3389
req.rdp_cookie_cnt([name])
Tries to parse the request buffer as RDP protocol, then returns
an integer corresponding to the number of RDP cookies found. If
an optional cookie name is passed, only cookies matching this
name are considered. This is mostly used in ACL.
req.ssl_hello_type
Returns an integer value containing the type of the SSL hello
message found in the request buffer. Note that this only applies
to raw contents found in the request buffer and not to contents
deciphered via an SSL data layer, so this will not work with
"bind" lines having the "ssl" option. This is mostly used in
ACL.
req.ssl_sni Returns a string containing the value of the Server Name TLS
extension sent by a client in a TLS stream passing through the
request buffer. Note that this only applies to raw contents
found in the request buffer and not to contents deciphered via
an SSL data layer, so this will not work with "bind" lines
having the "ssl" option. This is mostly used in ACL.
req.ssl_ver Returns an integer value containing the version of the SSL/TLS
protocol of a stream present in the request buffer. The value is
composed of the major version multiplied by 65536, added to the
minor version. Note that this only applies to raw contents found
in the request buffer and not to contents deciphered via an SSL
data layer, so this will not work with "bind" lines having the
"ssl" option. This is mostly used in ACL.
req.ver Returns the version string from the HTTP request, for example
"1.1". This can be useful for logs, but is mostly there for ACL.
req_len This is an alias for "req.len".
req_proto_http
This is an alias for "req_proto_http".
req_ssl_hello_type
This is an alias for "req.ssl_hello_type".
req_ssl_sni This is an alias for "req.ssl_sni".
req_ssl_ver This is an alias for "req.ssl_ver".
req_ver This is an alias for "req.ver".
res.comp Returns the boolean "true" value if the response has been
compressed by HAProxy, otherwise returns boolean "false".
res.comp_algo
Returns a string containing the name of the algorithm used if
the response was compressed by HAProxy.
res.cook([<name>])
This extracts the last occurrence of the cookie name <name> on a
"Set-Cookie" header line from the response, and returns its
value as string. If no name is specified, the first cookie value
is returned.
res.cook_cnt([<name>])
Returns an integer value representing the number of occurrences of
the cookie <name> in the response, or all cookies if <name> is not
specified.
res.cook_val([<name>])
This extracts the last occurrence of the cookie name <name> on a
"Set-Cookie" header line from the response, and converts its
value to an integer which is returned. If no name is specified,
the first cookie value is returned.
res.hdr(<name>[,<occ>])
This extracts the last occurrence of header <name> in an HTTP
response. Optionally, a specific occurrence might be specified
as a position number. Positive values indicate a position from
the first occurrence, with 1 being the first one. Negative
values indicate positions relative to the last one, with -1
being the last one. This can be useful to learn some data into
a stick-table.
res.hdr_cnt([<name>])
Returns an integer value representing the number of occurrences
of response header field name <name>, or the total number of
header fields if <name> is not specified.
res.hdr_ip([<name>[,<occ>]])
This extracts the last occurrence of header <name> in an HTTP
response, convert it to an IPv4 or IPv6 address and returns this
address. Optionally, a specific occurrence might be specified as
a position number. Positive values indicate a position from the
first occurrence, with 1 being the first one. Negative values
indicate positions relative to the last one, with -1 being the
last one. This can be useful to learn some data into a stick
table.
res.hdr_val([<name>[,<occ>]])
This extracts the last occurrence of header <name> in an HTTP
response, and converts it to an integer value. Optionally, a
specific occurrence might be specified as a position number.
Positive values indicate a position from the first occurrence,
with 1 being the first one. Negative values indicate positions
relative to the last one, with -1 being the last one. This can
be useful to learn some data into a stick table.
res.payload(<offset>,<length>)
This extracts a binary block of <length> bytes and starting at
bytes <offset> in the response buffer.
res.payload_lv(<offset1>,<length>[,<offset2>])
This extracts a binary block. In a first step the size of the
block is read from the response request buffer at <offset> bytes
and considered coded on <length> bytes. In a second step data of
the block are read from buffer at <offset2> bytes (by default
<lengthoffset> + <lengthsize>). If <offset2> is prefixed by '+'
or '-', it is relative to <lengthoffset> + <lengthsize> else it
is absolute. Ex: see SSL session id example in "stick table"
chapter.
res.ssl_hello_type
Returns an integer value containing the type of the SSL hello
message found in the response buffer. Note that this only
applies to raw contents found in the response buffer and not to
contents deciphered via an SSL data layer, so this will not work
with "server" lines having the "ssl" option. This is mostly used
in ACL.
res.ver Returns the version string from the HTTP response, for example
"1.1". This can be useful for logs, but is mostly there for ACL.
resp_ver This is an alias for "res.ver".
sc1_bytes_in_rate
sc2_bytes_in_rate
Returns the average client-to-server bytes rate from the
currently tracked counters, measured in amount of bytes over the
period configured in the table. See also src_bytes_in_rate.
sc1_bytes_out_rate
sc2_bytes_out_rate
Returns the average server-to-client bytes rate from the
currently tracked counters, measured in amount of bytes over the
period configured in the table. See also src_bytes_out_rate.
sc1_clr_gpc0
sc2_clr_gpc0
Clears the first General Purpose Counter associated to the
currently tracked counters, and returns its previous value.
This is only useful when used by ACLs.
sc1_conn_cnt
sc2_conn_cnt
Returns the cumulated number of incoming connections from
currently tracked counters. See also src_conn_cnt.
sc1_conn_cur
sc2_conn_cur
Returns the current amount of concurrent connections tracking
the same tracked counters. This number is automatically
incremented when tracking begins and decremented when tracking
stops. See also src_conn_cur.
sc1_conn_rate
sc2_conn_rate
Returns the average connection rate from the currently tracked
counters, measured in amount of connections over the period
configured in the table. See also src_conn_rate.
sc1_get_gpc0
sc2_get_gpc0
Returns the value of the first General Purpose Counter
associated to the currently tracked counters. See also
src_get_gpc0 and sc1/sc2_inc_gpc0.
sc1_http_err_cnt
sc2_http_err_cnt
Returns the cumulated number of HTTP errors from the currently
tracked counters. This includes the both request errors and 4xx
error responses. See also src_http_err_cnt.
sc1_http_err_rate
sc2_http_err_rate
Returns the average rate of HTTP errors from the currently
tracked counters, measured in amount of errors over the period
configured in the table. This includes the both request errors
and 4xx error responses. See also src_http_err_rate.
sc1_http_req_cnt
sc2_http_req_cnt
Returns the cumulated number of HTTP requests from the currently
tracked counters. This includes every started request, valid or
not. See also src_http_req_cnt.
sc1_http_req_rate
sc2_http_req_rate
Returns the average rate of HTTP requests from the currently
tracked counters, measured in amount of requests over the period
configured in the table. This includes every started request,
valid or not. See also src_http_req_rate.
sc1_inc_gpc0
sc2_inc_gpc0
Increments the first General Purpose Counter associated to the
currently tracked counters, and returns its new value. This is
only useful when used by ACLs.
sc1_kbytes_in
sc2_kbytes_in
Returns the amount of client-to-server data from the currently
tracked counters, measured in kilobytes over the period
configured in the table. The value being stored as a 32-bit
integer, it wraps at 4 terabytes. See also src_kbytes_in.
sc1_kbytes_out
sc2_kbytes_out
Returns the amount of server-to-client data from the currently
tracked counters, measured in kilobytes over the period
configured in the table. The value being stored as a 32-bit
integer, it wraps at 4 terabytes. See also src_kbytes_out.
sc1_sess_cnt
sc2_sess_cnt
Returns the cumulated number of incoming connections that were
transformed into sessions, which means that they were accepted
by a "tcp-request connection" rule, from the currently tracked
counters. A backend may count more sessions than connections
because each connection could result in many backend sessions if
some HTTP keep-alive is performed over the connection with the
client. See also src_sess_cnt.
sc1_sess_rate
sc2_sess_rate
Returns the average session rate from the currently tracked
counters, measured in amount of sessions over the period
configured in the table. A session is a connection that got past
the early "tcp-request connection" rules. A backend may count
more sessions than connections because each connection could
result in many backend sessions if some HTTP keep-alive is
performed over the connection with the client. See also
src_sess_rate.
sc1_trackers
sc2_trackers
Returns the current amount of concurrent connections tracking
the same tracked counters. This number is automatically
incremented when tracking begins and decremented when tracking
stops. It differs from sc1_conn_cur in that it does not rely on
any stored information but on the table's reference count (the
"use" value which is returned by "show table" on the CLI). This
may sometimes be more suited for layer7 tracking. It can be used
to tell a server how many concurrent connections there are from
a given address for example.
scook([<name>])
This is an alias for "res.cook".
scook_cnt([<name>])
This is an alias for "res.cook_cnt".
scook_val([<name>])
This is an alias for "res.cook_val".
set-cookie(<name>)
This fetch function is deprecated and has been superseded by the
"cookie" fetch which is capable of handling both requests and
responses. This keyword will disappear soon.
This extracts the last occurrence of the cookie name <name> on a
"Set-Cookie" header line from the response and uses the
corresponding value to match. This can be comparable to what
"appsession" does with default options, but with support for
multi-peer synchronization and state keeping across restarts.See also : "appsession"
shdr(<name>[,<occ>])
This is an alias for "res.hdr".
shdr_cnt([<name>])
This is an alias for "res.hdr_cnt".
shdr_ip([<name>[,<occ>]])
This is an alias for "res.hdr_ip".
shdr_val([<name>[,<occ>]])
This is an alias for "res.hdr_val".
so_id Returns an integer containing the listening socket's id.
src This is the source IPv4 address of the client of the session.
It is of type IPv4 and works on both IPv4 and IPv6 tables.
On IPv6 tables, IPv4 address is mapped to its IPv6 equivalent,
according to RFC 4291.
src_bytes_in_rate([<table>])
Returns the average bytes rate from the connection's source IPv4
address in the current proxy's stick-table or in the designated
stick-table, measured in amount of bytes over the period
configured in the table. If the address is not found, zero is
returned. See also sc1/sc2_bytes_in_rate.
src_bytes_out_rate([<table>])
Returns the average bytes rate to the connection's source IPv4
address in the current proxy's stick-table or in the designated
stick-table, measured in amount of bytes over the period
configured in the table. If the address is not found, zero is
returned. See also sc1/sc2_bytes_out_rate.
src_clr_gpc0([<table>])
Clears the first General Purpose Counter associated to the
connection's source IPv4 address in the current proxy's
stick-table or in the designated stick-table, and returns its
previous value. This is only useful when used by ACLs.
src_conn_cnt([<table>])
Returns the cumulated number of connections initiated from the
current connection's source IPv4 address in the current proxy's
stick-table or in the designated stick-table. If the address is
not found, zero is returned. See also sc1/sc2_conn_cnt.
src_conn_cur([<table>])
Returns the current amount of concurrent connections initiated
from the current connection's source IPv4 address in the current
proxy's stick-table or in the designated stick-table. If the
address is not found, zero is returned. See also
sc1/sc2_conn_cur.
src_conn_rate([<table>])
Returns the average connection rate from the connection's source
IPv4 address in the current proxy's stick-table or in the
designated stick-table, measured in amount of connections over
the period configured in the table. If the address is not found,
zero is returned. See also sc1/sc2_conn_rate.
src_get_gpc0([<table>])
Returns the value of the first General Purpose Counter
associated to the connection's source IPv4 address in the
current proxy's stick-table or in the designated stick-table. If
the address is not found, zero is returned. See also
sc1/sc2_get_gpc0 and src_inc_gpc0.
src_http_err_cnt([<table>])
Returns the cumulated number of HTTP errors from the current
connection's source IPv4 address in the current proxy's
stick-table or in the designated stick-table. This includes the
both request errors and 4xx error responses. If the address is
not found, zero is returned. See also sc1/sc2_http_err_cnt.
src_http_err_rate([<table>])
Returns the average rate of HTTP errors from the current
connection's source IPv4 address in the current proxy's
stick-table or in the designated stick- table, measured in
amount of errors over the period configured in the table. This
includes the both request errors and 4xx error responses. If the
address is not found, zero is returned. See also
sc1/sc2_http_err_rate.
src_http_req_cnt([<table>])
Returns the cumulated number of HTTP requests from the current
connection's source IPv4 address in the current proxy's
stick-table or in the designated stick-table. This includes
every started request, valid or not. If the address is not
found, zero is returned. See also sc1/sc2_http_req_cnt.
src_http_req_rate([<table>])
Returns the average rate of HTTP requests from the current
connection's source IPv4 address in the current proxy's
stick-table or in the designated stick-table, measured in amount
of requests over the period configured in the table. This
includes every started request, valid or not. If the address is
not found, zero is returned. See also sc1/sc2_http_req_rate.
src_inc_gpc0([<table>])
Increments the first General Purpose Counter associated to the
connection's source IPv4 address in the current proxy's
stick-table or in the designated stick-table, and returns its
new value. This is only useful when used by ACLs.
src_kbytes_in([<table>])
Returns the amount of data received from the connection's source
IPv4 address in the current proxy's stick-table or in the
designated stick-table, measured in kilobytes over the period
configured in the table. If the address is not found, zero is
returned. The value being stored as a 32-bit integer, it wraps
at 4 terabytes. See also sc1/sc2_kbytes_in.
src_kbytes_out([<table>])
Returns the amount of data sent to the connection's source IPv4
address in the current proxy's stick-table or in the designated
stick-table, measured in kilobytes over the period configured in
the table. If the address is not found, zero is returned. The
value being stored as a 32-bit integer, it wraps at 4 terabytes.
See also sc1/sc2_kbytes_out.
src_port This is the source TCP port of the session on the client side,
which is the port the client connected from. It is very unlikely
that this function will be useful but it's available at no cost.
It is of type integer and only works with such tables.
src_sess_cnt([<table>])
Returns the cumulated number of connections initiated from the
current connection's source IPv4 address in the current proxy's
stick-table or in the designated stick-table, that were
transformed into sessions, which means that they were accepted
by "tcp-request" rules. If the address is not found, zero is
returned. See also sc1/sc2_sess_cnt.
src_sess_rate([<table>])
Returns the average session rate from the connection's source
IPv4 address in the current proxy's stick-table or in the
designated stick-table, measured in amount of sessions over the
period configured in the table. A session is a connection that
got past the early "tcp-request" rules. If the address is not
found, zero is returned. See also sc1/sc2_sess_rate.
src_updt_conn_cnt([<table>])
Creates or updates the entry associated to the source IPv4
address in the current proxy's stick-table or in the designated
stick-table. This is only useful when used by ACLs.
srv_conn(<backend>/<server>)
Returns an integer value corresponding to the number of
currently established connections on this server, possibly
including the connection being evaluated. It is only used with
ACLs.
srv_id Returns an integer containing the server's id when processing
the response. While it's almost only used with ACLs, it may be
used for logging or debugging.
srv_is_up([<backend>/]<server>)
Returns a the boolean TRUE value when the designated server is
UP, and false when it is either DOWN or in maintenance mode. If
<backend> is omitted, then the server is looked up in the
current backend. It is almost only used with ACLs.
srv_sess_rate(<backend>/<server>)
Returns an integer corresponding to the sessions creation rate
on the server, in number of new sessions per second. This is
used with ACLs but may make sense with logs too.
ssl_c_ca_err Returns the ID of the first error detected during verify of the
client certificate at depth > 0, or 0 if no error was detected.
ssl_c_ca_err_depth
Returns the depth of the first error detected during verify. If
no error is encountered in the CA chain, zero is returned.
ssl_c_err Returns the ID of the first error detected during verify of the
client certificate at depth == 0, or 0 if no errors.
ssl_c_i_dn[(entry[,occ])]
If no entry specified, returns the full distinguished name of
the issuer of the certificate presented by the client when
the incoming connection was made over an SSL/TLS transport
layer. Otherwise returns the value of the first given entry
found from the beginning of the DN. If a positive/negative
occurrence number is specified as the optional second argument,
it returns the value of the nth given entry found from the
beginning/end of the DN. For instance to retrieve the common
name ssl_c_i_dn(CN) and the second organization unit
ssl_c_i_dn(OU,2).
ssl_c_key_alg
Returns the name of the algorithm used to generate the key of
the certificate presented by the client when the incoming
connection was made over an SSL/TLS transport layer.
ssl_c_notafter
Returns the end date presented by the client as a formatted
string YYMMDDhhmmss[Z] when the incoming connection was made
over an SSL/TLS transport layer.
ssl_c_notbefore
Returns the start date presented by the client as a formatted
string YYMMDDhhmmss[Z] when the incoming connection was made
over an SSL/TLS transport layer.
ssl_c_s_dn[(entry[,occ])]
If no entry specified, returns the full distinguished name of
the subject of the certificate presented by the client when
the incoming connection was made over an SSL/TLS transport
layer. Otherwise returns the value of the first given entry
found from the beginning of the DN. If a positive/negative
occurrence number is specified as the optional second argument,
it returns the value of the nth given entry found from the
beginning/end of the DN. For instance to retrieve the common
name ssl_c_s_dn(CN) and the second organization unit
ssl_c_s_dn(OU,2).
ssl_c_serial Returns the serial of the certificate presented by the client
when the incoming connection was made over an SSL/TLS transport
layer.
ssl_c_sha1 Returns the SHA-1 fingerprint of the certificate presented by
the client when the incoming connection was made over an SSL/TLS
transport layer. This can be used to stick a client to a server,
or to pass this information to a server.
ssl_c_sig_alg
Returns the name of the algorithm used to sign the certificate
presented by the client when the incoming connection was made
over an SSL/TLS transport layer.
ssl_c_used
Returns 1 if current SSL session use a client certificate,
otherwise 0. See also "ssl_fc_has_crt".
ssl_c_verify Returns the verify result errorID when the incoming connection
was made over an SSL/TLS transport layer, otherwise zero if no
error is encountered.
ssl_c_version
Returns the version of the certificate presented by the client
when the incoming connection was made over an SSL/TLS transport
layer.
ssl_f_i_dn[(entry[,occ])]
If no entry specified, returns the full distinguished name of
the issuer of the certificate presented by the frontend when
the incoming connection was made over an SSL/TLS transport
layer. Otherwise returns the value of the first given entry
found from the beginning of the DN. If a positive/negative
occurrence number is specified as the optional second argument,
it returns the value of the nth given entry found from the
beginning/end of the DN. For instance to retrieve the common
name ssl_f_i_dn(CN) and the second organization unit
ssl_f_i_dn(OU,2).
ssl_f_key_alg
Returns the name of the algorithm used to generate the key of
the certificate presented by the frontend when the incoming
connection was made over an SSL/TLS transport layer.
ssl_f_notafter
Returns the end date presented by the frontend as a formatted
string YYMMDDhhmmss[Z] when the incoming connection was made
over an SSL/TLS transport layer.
ssl_f_notbefore
Returns the start date presented by the frontend as a formatted
string YYMMDDhhmmss[Z] when the incoming connection was made
over an SSL/TLS transport layer.
ssl_f_s_dn[(entry[,occ])]
If no entry specified, returns the full distinguished name of
the subject of the certificate presented by the frontend when
the incoming connection was made over an SSL/TLS transport
layer. Otherwise returns the value of the first given entry
found from the beginning of the DN. If a positive/negative
occurrence number is specified as the optional second argument,
it returns the value of the nth given entry found from the
beginning/end of the DN. For instance to retrieve the common
name ssl_f_s_dn(CN) and the second organization unit
ssl_f_s_dn(OU,2).
ssl_f_serial Returns the serial of the certificate presented by the frontend
when the incoming connection was made over an SSL/TLS transport
layer.
ssl_f_sig_alg
Returns the name of the algorithm used to sign the certificate
presented by the frontend when the incoming connection was made
over an SSL/TLS transport layer.
ssl_f_version
Returns the version of the certificate presented by the frontend
when the incoming connection was made over an SSL/TLS transport
layer.
ssl_fc This checks the transport layer used on the front connection,
and returns 1 if it was made via an SSL/TLS transport layer,
otherwise zero.
ssl_fc_alg_keysize
Returns the symmetric cipher key size support d in bits when the
incoming connection was made over an SSL/TLS transport layer.
ssl_fc_cipher
Returns the name of the used cipher when the incoming connection
was made over an SSL/TLS transport layer.
ssl_fc_has_crt
Returns 1 if a client certificate is present in the front
connection over SSL/TLS transport layer, otherwise 0.
Note: on SSL session resumption with Session ID or TLS ticket,
client certificate is not present in the current connection but
may be retrieved from the cache or the ticket. So prefer
"ssl_c_used" if you want to check if current SSL session uses
a client certificate.
ssl_fc_has_sni
This checks the transport layer used by the front connection, and
returns 1 if the connection was made via an SSL/TLS transport
layer and the client sent a Server Name Indication TLS extension,
otherwise zero. This requires that the SSL library is build with
support for TLS extensions enabled (check haproxy -vv).
ssl_fc_npn This extracts the Next Protocol Negociation field from an
incoming connection made via an SSL/TLS transport layer and
locally deciphered by haproxy. The result is a string containing
the protocol name advertised by the client. The SSL library must
have been built with support for