Haproxy Configure File

----------------------
HAProxy
Configuration Manual
----------------------
version 1.5.11
willy tarreau
2015/02/01

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
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please update the summary below for easier searching.

Summary
-------

1. Quick reminder about HTTP
1.1. The HTTP transaction model
1.2. HTTP request
1.2.1. The Request line
1.2.2. The request headers
1.3. HTTP response
1.3.1. The Response line
1.3.2. The response headers

2. Configuring HAProxy
2.1. Configuration file format
2.2. Time format
2.3. Examples

3. Global parameters
3.1. Process management and security
3.2. Performance tuning
3.3. Debugging
3.4. Userlists
3.5. Peers

4. Proxies
4.1. Proxy keywords matrix
4.2. Alphabetically sorted keywords reference

5. Bind and Server options
5.1. Bind options
5.2. Server and default-server options

6. HTTP header manipulation

7. Using ACLs and fetching samples
7.1. ACL basics
7.1.1. Matching booleans
7.1.2. Matching integers
7.1.3. Matching strings
7.1.4. Matching regular expressions (regexes)
7.1.5. Matching arbitrary data blocks
7.1.6. Matching IPv4 and IPv6 addresses
7.2. Using ACLs to form conditions
7.3. Fetching samples
7.3.1. Converters
7.3.2. Fetching samples from internal states
7.3.3. Fetching samples at Layer 4
7.3.4. Fetching samples at Layer 5
7.3.5. Fetching samples from buffer contents (Layer 6)
7.3.6. Fetching HTTP samples (Layer 7)
7.4. Pre-defined ACLs

8. Logging
8.1. Log levels
8.2. Log formats
8.2.1. Default log format
8.2.2. TCP log format
8.2.3. HTTP log format
8.2.4. Custom log format
8.2.5. Error log format
8.3. Advanced logging options
8.3.1. Disabling logging of external tests
8.3.2. Logging before waiting for the session to terminate
8.3.3. Raising log level upon errors
8.3.4. Disabling logging of successful connections
8.4. Timing events
8.5. Session state at disconnection
8.6. Non-printable characters
8.7. Capturing HTTP cookies
8.8. Capturing HTTP headers
8.9. Examples of logs

9. Statistics and monitoring
9.1. CSV format
9.2. Unix Socket commands

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.

HAProxy supports 5 connection modes :
- keep alive : all requests and responses are processed (default)
- tunnel : only the first request and response are processed,
everything else is forwarded with no analysis.
- passive close : tunnel with "Connection: close" added in both directions.
- server close : the server-facing connection is closed after the response.
- forced close : the connection is actively closed after end of response.

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/png

1.2.1. 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 -c

3. 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
- ssl-server-verify
- node
- description
- unix-bind

* Performance tuning
- max-spread-checks
- maxconn
- maxconnrate
- maxcomprate
- maxcompcpuusage
- maxpipes
- maxsessrate
- maxsslconn
- maxsslrate
- noepoll
- nokqueue
- nopoll
- nosplice
- nogetaddrinfo
- spread-checks
- tune.bufsize
- tune.chksize
- tune.comp.maxlevel
- tune.http.cookielen
- tune.http.maxhdr
- tune.idletimer
- 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.force-private-cache
- tune.ssl.maxrecord
- tune.ssl.default-dh-param
- tune.zlib.memlevel
- tune.zlib.windowsize

* Debugging
- debug
- quiet

3.1. Process management and security
------------------------------------

ca-base <dir>
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".

chroot <jail dir>
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.

cpu-map <"all"|"odd"|"even"|process_num> <cpu-set>...
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 or
64, depending on the machine's word size, 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 63 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.

crt-base <dir>
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".

daemon
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.

gid <number>
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".

group <group name>
Similar to "gid" but uses the GID of group name <group name> from /etc/group.
See also "gid" and "user".

log <address> [len <length>] <facility> [max level [min level]]
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.

<length> is an optional maximum line length. Log lines larger than this value
will be truncated before being sent. The reason is that syslog
servers act differently on log line length. All servers support the
default value of 1024, but some servers simply drop larger lines
while others do log them. If a server supports long lines, it may
make sense to set this value here in order to avoid truncating long
lines. Similarly, if a server drops long lines, it is preferable to
truncate them before sending them. Accepted values are 80 to 65535
inclusive. The default value of 1024 is generally fine for all
standard usages. Some specific cases of long captures or
JSON-formated logs may require larger values.

<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

log-send-hostname [<string>]
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.

log-tag <string>
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.

nbproc <number>
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".

pidfile <pidfile>
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".

stats bind-process [ all | odd | even | <number 1-64>[-<number 1-64>] ] ...
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. The maximum process ID depends on the machine's
word size (32 or 64). A better option consists in using the "process" setting
of the "stats socket" line to force the process on each line.

ssl-default-bind-ciphers <ciphers>
This setting is only available when support for OpenSSL was built in. It sets
the default string describing the list of cipher algorithms ("cipher suite")
that are negotiated during the SSL/TLS handshake for all "bind" lines which
do not explicitly define theirs. 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). Please check the
"bind" keyword for more information.

ssl-default-bind-options [<option>]...
This setting is only available when support for OpenSSL was built in. It sets
default ssl-options to force on all "bind" lines. Please check the "bind"
keyword to see available options.

Example:
global
ssl-default-bind-options no-sslv3 no-tls-tickets

ssl-default-server-ciphers <ciphers>
This setting is only available when support for OpenSSL was built in. It
sets the default string describing the list of cipher algorithms that are
negotiated during the SSL/TLS handshake with the server, for all "server"
lines which do not explicitly define theirs. The format of the string is
defined in "man 1 ciphers". Please check the "server" keyword for more
information.

ssl-default-server-options [<option>]...
This setting is only available when support for OpenSSL was built in. It sets
default ssl-options to force on all "server" lines. Please check the "server"
keyword to see available options.

ssl-server-verify [none|required]
The default behavior for SSL verify on servers side. If specified to 'none',
servers certificates are not verified. The default is 'required' except if
forced using cmdline option '-dV'.

stats socket [<address:port>|<path>] [param*]
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.

stats timeout <timeout, in milliseconds>
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 }.

stats maxconn <connections>
By default, the stats socket is limited to 10 concurrent connections. It is
possible to change this value with "stats maxconn".

uid <number>
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".

ulimit-n <number>
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.

user <user name>
Similar to "uid" but uses the UID of user name <user name> from /etc/passwd.
See also "uid" and "group".

node <name>
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.

description <text>
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
-----------------------

max-spread-checks <delay in milliseconds>
By default, haproxy tries to spread the start of health checks across the
smallest health check interval of all the servers in a farm. The principle is
to avoid hammering services running on the same server. But when using large
check intervals (10 seconds or more), the last servers in the farm take some
time before starting to be tested, which can be a problem. This parameter is
used to enforce an upper bound on delay between the first and the last check,
even if the servers' check intervals are larger. When servers run with
shorter intervals, their intervals will be respected though.

maxconn <number>
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". Note:
the "select" poller cannot reliably use more than 1024 file descriptors on
some platforms. If your platform only supports select and reports "select
FAILED" on startup, you need to reduce maxconn until it works (slightly
below 500 in general).

maxconnrate <number>
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.

maxcomprate <number>
Sets the maximum per-process input compression rate to <number> kilobytes
per 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.

maxcompcpuusage <number>
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.

maxpipes <number>
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.

maxsessrate <number>
Sets the maximum per-process number of sessions 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.

maxsslconn <number>
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.

maxsslrate <number>
Sets the maximum per-process number of SSL sessions per second to <number>.
SSL listeners will stop accepting connections when this limit is reached. It
can be used to limit the global SSL CPU usage 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. It is also important to
note that the sessions are accounted before they enter the SSL stack and not
after, which also protects the stack against bad handshakes. Also, lowering
tune.maxaccept can improve fairness.

maxzlibmem <number>
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.

noepoll
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".

nokqueue
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".

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".

nosplice
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".

nogetaddrinfo
Disables the use of getaddrinfo(3) for name resolving. It is equivalent to
the command line argument "-dG". Deprecated gethostbyname(3) will be used.

spread-checks <0..50, in percent>
Sometimes it is desirable to avoid sending agent and 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.

tune.bufsize <number>
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).

tune.chksize <number>
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.

tune.comp.maxlevel <number>
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.

tune.http.cookielen <number>
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.

tune.http.maxhdr <number>
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.

tune.idletimer <timeout>
Sets the duration after which haproxy will consider that an empty buffer is
probably associated with an idle stream. This is used to optimally adjust
some packet sizes while forwarding large and small data alternatively. The
decision to use splice() or to send large buffers in SSL is modulated by this
parameter. The value is in milliseconds between 0 and 65535. A value of zero
means that haproxy will not try to detect idle streams. The default is 1000,
which seems to correctly detect end user pauses (eg: read a page before
clicking). There should be not reason for changing this value. Please check
tune.ssl.maxrecord below.

tune.maxaccept <number>
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.

tune.maxpollevents <number>
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.

tune.maxrewrite <number>
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.

tune.pipesize <number>
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.

tune.rcvbuf.client <number>
tune.rcvbuf.server <number>
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.

tune.sndbuf.client <number>
tune.sndbuf.server <number>
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.

tune.ssl.cachesize <number>
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 uses approximately
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.

tune.ssl.force-private-cache
This boolean disables SSL session cache sharing between all processes. It
should normally not be used since it will force many renegotiations due to
clients hitting a random process. But it may be required on some operating
systems where none of the SSL cache synchronization method may be used. In
this case, adding a first layer of hash-based load balancing before the SSL
layer might limit the impact of the lack of session sharing.

tune.ssl.lifetime <timeout>
Sets how long a cached SSL session may remain valid. This time is expressed
in seconds and defaults to 300 (5 min). 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.

tune.ssl.maxrecord <number>
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. Haproxy will automatically switch to this setting after an idle
stream has been detected (see tune.idletimer above).

tune.ssl.default-dh-param <number>
Sets the maximum size of the Diffie-Hellman parameters used for generating
the ephemeral/temporary Diffie-Hellman key in case of DHE key exchange. The
final size will try to match the size of the server's RSA (or DSA) key (e.g,
a 2048 bits temporary DH key for a 2048 bits RSA key), but will not exceed
this maximum value. Default value if 1024. Only 1024 or higher values are
allowed. Higher values will increase the CPU load, and values greater than
1024 bits are not supported by Java 7 and earlier clients. This value is not
used if static Diffie-Hellman parameters are supplied via the certificate file.

tune.zlib.memlevel <number>
Sets the memLevel parameter in zlib initialization for each session. It
defines how much memory should be allocated for the internal 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.

tune.zlib.windowsize <number>
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
--------------

debug
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.

quiet
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.

userlist <listname>
Creates new userlist with name <listname>. Many independent userlists can be
used to store authentication & authorization data for independent customers.

group <groupname> [users <user>,<user>,(...)]
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.

user <username> [password|insecure-password <password>]
[groups <group>,<group>,(...)]
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 encrypting 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.

peers <peersect>
Creates a new peer list with name <peersect>. It is an independent section,
which is referenced by one or more stick-tables.

peer <peername> <ip>:<port>
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.

In HTTP mode, the processing applied to requests and responses flowing over
a connection depends in the combination of the frontend's HTTP options and
the backend's. HAProxy supports 5 connection modes :

- KAL : keep alive ("option http-keep-alive") which is the default mode : all
requests and responses are processed, and connections remain open but idle
between responses and new requests.

- TUN: tunnel ("option http-tunnel") : this was the default mode for versions
1.0 to 1.5-dev21 : only the first request and response are processed, and
everything else is forwarded with no analysis at all. This mode should not
be used as it creates lots of trouble with logging and HTTP processing.

- PCL: passive close ("option httpclose") : exactly the same as tunnel mode,
but with "Connection: close" appended in both directions to try to make
both ends close after the first request/response exchange.

- SCL: server close ("option http-server-close") : the server-facing
connection is closed after the end of the response is received, but the
client-facing connection remains open.

- FCL: forced close ("option forceclose") : the connection is actively closed
after the end of the response.

The effective mode that will be applied to a connection passing through a
frontend and a backend can be determined by both proxy modes according to the
following matrix, but in short, the modes are symmetric, keep-alive is the
weakest option and force close is the strongest.

Backend mode

| KAL | TUN | PCL | SCL | FCL
----+-----+-----+-----+-----+----
KAL | KAL | TUN | PCL | SCL | FCL
----+-----+-----+-----+-----+----
TUN | TUN | TUN | PCL | SCL | FCL
Frontend ----+-----+-----+-----+-----+----
mode PCL | PCL | PCL | PCL | FCL | FCL
----+-----+-----+-----+-----+----
SCL | SCL | SCL | FCL | SCL | FCL
----+-----+-----+-----+-----+----
FCL | FCL | FCL | FCL | FCL | FCL

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.

keyword defaults frontend listen backend
------------------------------------+----------+----------+---------+---------
acl - X X X
appsession - - X X
backlog X X X -
balance X - X X
bind - X X -
bind-process X X X X
block - X X X
capture cookie - X X -
capture request header - X X -
capture response header - X X -
clitimeout (deprecated) X X X -
compression X X X X
contimeout (deprecated) X - X X
cookie X - X X
default-server X - X X
default_backend X X X -
description - X X X
disabled X X X X
dispatch - - X X
enabled X X X X
errorfile X X X X
errorloc X X X X
errorloc302 X X X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
errorloc303 X X X X
force-persist - X X X
fullconn X - X X
grace X X X X
hash-type X - X X
http-check disable-on-404 X - X X
http-check expect - - X X
http-check send-state X - X X
http-request - X X X
http-response - X X X
http-send-name-header - - X X
id - X X X
ignore-persist - X X X
log (*) X X X X
log-format X X X -
max-keep-alive-queue X - X X
maxconn X X X -
mode X X X X
monitor fail - X X -
monitor-net X X X -
monitor-uri X X X -
option abortonclose (*) X - X X
option accept-invalid-http-request (*) X X X -
option accept-invalid-http-response (*) X - X X
option allbackups (*) X - X X
option checkcache (*) X - X X
option clitcpka (*) X X X -
option contstats (*) X X X -
option dontlog-normal (*) X X X -
option dontlognull (*) X X X -
option forceclose (*) X X X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
option forwardfor X X X X
option http-keep-alive (*) X X X X
option http-no-delay (*) X X X X
option http-pretend-keepalive (*) X X X X
option http-server-close (*) X X X X
option http-tunnel (*) X X X X
option http-use-proxy-header (*) X X X -
option httpchk X - X X
option httpclose (*) X X X X
option httplog X X X X
option http_proxy (*) X X X X
option independent-streams (*) X X X X
option ldap-check X - X X
option log-health-checks (*) X - X X
option log-separate-errors (*) X X X -
option logasap (*) X X X -
option mysql-check X - X X
option pgsql-check X - X X
option nolinger (*) X X X X
option originalto X X X X
option persist (*) X - X X
option redispatch (*) X - X X
option redis-check X - X X
option smtpchk X - X X
option socket-stats (*) X X X -
option splice-auto (*) X X X X
option splice-request (*) X X X X
option splice-response (*) X X X X
option srvtcpka (*) X - X X
option ssl-hello-chk X - X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
option tcp-check X - X X
option tcp-smart-accept (*) X X X -
option tcp-smart-connect (*) X - X X
option tcpka X X X X
option tcplog X X X X
option transparent (*) X - X X
persist rdp-cookie X - X X
rate-limit sessions X X X -
redirect - X X X
redisp (deprecated) X - X X
redispatch (deprecated) X - X X
reqadd - X X X
reqallow - X X X
reqdel - X X X
reqdeny - X X X
reqiallow - X X X
reqidel - X X X
reqideny - X X X
reqipass - X X X
reqirep - X X X
reqisetbe - X X X
reqitarpit - X X X
reqpass - X X X
reqrep - X X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
reqsetbe - X X X
reqtarpit - X X X
retries X - X X
rspadd - X X X
rspdel - X X X
rspdeny - X X X
rspidel - X X X
rspideny - X X X
rspirep - X X X
rsprep - X X X
server - - X X
source X - X X
srvtimeout (deprecated) X - X X
stats admin - - X X
stats auth X - X X
stats enable X - X X
stats hide-version X - X X
stats http-request - - X X
stats realm X - X X
stats refresh X - X X
stats scope X - X X
stats show-desc X - X X
stats show-legends X - X X
stats show-node X - X X
stats uri X - X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
stick match - - X X
stick on - - X X
stick store-request - - X X
stick store-response - - X X
stick-table - - X X
tcp-check connect - - X X
tcp-check expect - - X X
tcp-check send - - X X
tcp-check send-binary - - X X
tcp-request connection - X X -
tcp-request content - X X X
tcp-request inspect-delay - X X X
tcp-response content - - X X
tcp-response inspect-delay - - X X
timeout check X - X X
timeout client X X X -
timeout client-fin X X X -
timeout clitimeout (deprecated) X X X -
timeout connect X - X X
timeout contimeout (deprecated) X - X X
timeout http-keep-alive X X X X
timeout http-request X X X X
timeout queue X - X X
timeout server X - X X
timeout server-fin X - X X
timeout srvtimeout (deprecated) X - X X
timeout tarpit X X X X
timeout tunnel X - X X
transparent (deprecated) X - X X
unique-id-format X X X -
unique-id-header X X X -
use_backend - X X -
use-server - - X X
------------------------------------+----------+----------+---------+---------
keyword defaults frontend listen backend

4.2. Alphabetically sorted keywords reference
---------------------------------------------

This section provides a description of each keyword and its usage.

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".

backlog <conns>
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.

balance <algorithm> [ <arguments> ]
balance url_param <param> [check_post]
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 4095 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 chosen 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. The message body will only start to be
analyzed once either the advertised amount of data has been
received or the request buffer is full. In the unlikely event
that chunked encoding is used, only the first chunk is
scanned. Parameter values separated by a chunk boundary, may
be randomly balanced if at all. This keyword used to support
an optional <max_wait> parameter which is now ignored.

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.

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.

See also : "dispatch", "cookie", "appsession", "transparent", "hash-type" and
"http_proxy".

bind [<address>]:<port_range> [, ...] [param*]
bind /<path> [, ...] [param*]
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
- 'abns@' -> address is in abstract namespace (Linux only).
Note: since abstract sockets are not "rebindable", they
do not cope well with multi-process mode during
soft-restart, so it is better to avoid them if
nbproc is greater than 1. The effect is that if the
new process fails to start, only one of the old ones
will be able to rebind to the 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.

odd This instance will be enabled on processes 1,3,5,...63. This
option may be combined with other numbers.

even This instance will be enabled on processes 2,4,6,...64. 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 or 64 depending on
the machine's word size. If a proxy is bound to process
numbers greater than the configured global.nbproc, it will
either be forced to process #1 if a single process was
specified, or to all processes otherwise.

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 or 64 processes
using this keyword, but this should be more than enough for most setups.
Please note that 'all' really means all processes regardless of the machine's
word size, and is not limited to the first 32 or 64.

Each "bind" line may further be limited to a subset of the proxy's processes,
please consult the "process" bind keyword in section 5.1.

When a frontend has no explicit "bind-process" line, it tries to bind to all
the processes referenced by its "bind" lines. That means that frontends can
easily adapt to their listeners' processes.

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, and "process" in section 5.1.

block { if | unless } <condition>
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 cookie <name> len <length>
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

See also : "capture request header", "capture response header" as well as
section 8 about logging.

capture request header <name> len <length>
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

See also : "capture cookie", "capture response header" as well as section 8
about logging.

capture response header <name> len <length>
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

See also : "capture cookie", "capture request header" as well as section 8
about logging.

clitimeout <timeout> (deprecated)
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.

See also : "timeout client", "timeout http-request", "timeout server", and
"srvtimeout".

compression algo <algorithm> ...
compression type <mime type> ...
compression offload
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. Note: for now, the "offload" setting is
ignored when set in a defaults section.

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 header "Transfer-Encoding" contains "chunked" (Temporary
Workaround)
* 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

contimeout <timeout> (deprecated)
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.

See also : "timeout connect", "timeout queue", "timeout tarpit",
"timeout server", "contimeout".

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

See also : "appsession", "balance source", "capture cookie", "server"
and "ignore-persist".

default-server [param*]
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

See also: "server" and section 5 about server options

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"

Allows to add a sentence to describe the related object in the HAProxy HTML
stats page. The description will be printed on the right of the object name
it describes.
No need to backslash spaces in the <string> arguments.

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: "unique-id-format"

use_backend <backend> [{if | unless} <condition>]
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, or a
"log-format" string resolving to a backend name.

<condition> is a condition composed of ACLs, as described in section 7. If
it is omitted, the rule is unconditionally applied.

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.

When <backend> is a simple name, it is resolved at configuration time, and an
error is reported if the specified backend does not exist. If <backend> is
a log-format string instead, no check may be done at configuration time, so
the backend name is resolved dynamically at run time. If the resulting
backend name does not correspond to any valid backend, no other rule is
evaluated, and the default_backend directive is applied instead. Note that
when using dynamic backend names, it is highly recommended to use a prefix
that no other backend uses in order to ensure that an unauthorized backend
cannot be forced from the request.

It is worth mentioning that "use_backend" rules with an explicit name are
used to detect the association between frontends and backends to compute the
backend's "fullconn" setting. This cannot be done for dynamic names.

See also: "default_backend", "tcp-request", "fullconn", "log-format", and
section 7 about ACLs.

use-server <server> if <condition>
use-server <server> unless <condition>
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", section 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.

accept-proxy
Enforces the use of the PROXY protocol over any connection accepted by any of
the sockets declared on the same line. Versions 1 and 2 of the PROXY protocol
are supported and correctly detected. 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. See also "tcp-request connection expect-proxy" for a finer-grained
setting of which client is allowed to use the protocol.

alpn <protocols>
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.

backlog <backlog>
Sets the socket's backlog to this value. If unspecified, the frontend's
backlog is used instead, which generally defaults to the maxconn value.

ecdhe <named curve>
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.

ca-file <cafile>
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.

ca-ignore-err [all|<errorID>,...]
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.

ciphers <ciphers>
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
negotiated 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).

crl-file <crlfile>
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.

crt <cert>
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 in alphabetic order unless their name ends with
'.issuer' or '.ocsp' (reserved extensions). 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 or to ensure that it will
always be the first one in the directory.

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 an 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).

For each PEM file, haproxy checks for the presence of file at the same path
suffixed by ".ocsp". If such file is found, support for the TLS Certificate
Status Request extension (also known as "OCSP stapling") is automatically
enabled. The content of this file is optional. If not empty, it must contain
a valid OCSP Response in DER format. In order to be valid an OCSP Response
must comply with the following rules: it has to indicate a good status,
it has to be a single response for the certificate of the PEM file, and it
has to be valid at the moment of addition. If these rules are not respected
the OCSP Response is ignored and a warning is emitted. In order to identify
which certificate an OCSP Response applies to, the issuer's certificate is
necessary. If the issuer's certificate is not found in the PEM file, it will
be loaded from a file at the same path as the PEM file suffixed by ".issuer"
if it exists otherwise it will fail with an error.

crt-ignore-err <errors>
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.

crt-list <file>
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.

defer-accept
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.

force-sslv3
This option enforces use of SSLv3 only on SSL connections instantiated from
this listener. SSLv3 is generally less expensive than the TLS counterparts
for high connection rates. This option is also available on global statement
"ssl-default-bind-options". See also "no-tlsv*" and "no-sslv3".

force-tlsv10
This option enforces use of TLSv1.0 only on SSL connections instantiated from
this listener. This option is also available on global statement
"ssl-default-bind-options". See also "no-tlsv*" and "no-sslv3".

force-tlsv11
This option enforces use of TLSv1.1 only on SSL connections instantiated from
this listener. This option is also available on global statement
"ssl-default-bind-options". See also "no-tlsv*", and "no-sslv3".

force-tlsv12
This option enforces use of TLSv1.2 only on SSL connections instantiated from
this listener. This option is also available on global statement
"ssl-default-bind-options". See also "no-tlsv*", and "no-sslv3".

gid <gid>
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.

group <group>
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.

id <id>
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.

interface <interface>
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.

level <level>
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).

maxconn <maxconn>
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.

mode <mode>
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.

mss <maxseg>
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.

name <name>
Sets an optional name for these sockets, which will be reported on the stats
page.

nice <nice>
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.

no-sslv3
This setting is only available when support for OpenSSL was built in. It
disables support for SSLv3 on any sockets instantiated from the listener when
SSL is supported. Note that SSLv2 is forced disabled in the code and cannot
be enabled using any configuration option. This option is also available on
global statement "ssl-default-bind-options". See also "force-tls*",
and "force-sslv3".

no-tls-tickets
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 option is also
available on global statement "ssl-default-bind-options".

no-tlsv10
This setting is only available when support for OpenSSL was built in. It
disables support for TLSv1.0 on any sockets instantiated from the listener
when SSL is supported. Note that SSLv2 is forced disabled in the code and
cannot be enabled using any configuration option. This option is also
available on global statement "ssl-default-bind-options". See also
"force-tlsv*", and "force-sslv3".

no-tlsv11
This setting is only available when support for OpenSSL was built in. It
disables support for TLSv1.1 on any sockets instantiated from the listener
when SSL is supported. Note that SSLv2 is forced disabled in the code and
cannot be enabled using any configuration option. This option is also
available on global statement "ssl-default-bind-options". See also
"force-tlsv*", and "force-sslv3".

no-tlsv12
This setting is only available when support for OpenSSL was built in. It
disables support for TLSv1.2 on any sockets instantiated from the listener
when SSL is supported. Note that SSLv2 is forced disabled in the code and
cannot be enabled using any configuration option. This option is also
available on global statement "ssl-default-bind-options". See also
"force-tlsv*", and "force-sslv3".

npn <protocols>
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).

process [ all | odd | even | <number 1-64>[-<number 1-64>] ]
This restricts the list of processes on which this listener is allowed to
run. It does not enforce any process but eliminates those which do not match.
If the frontend uses a "bind-process" setting, the intersection between the
two is applied. If in the end the listener is not allowed to run on any
remaining process, a warning is emitted, and the listener will either run on
the first process of the listener if a single process was specified, or on
all of its processes if multiple processes were specified. For the unlikely
case where several ranges are needed, this directive may be repeated. The
main purpose of this directive is to be used with the stats sockets and have
one different socket per process. The second purpose is to have multiple bind
lines sharing the same IP:port but not the same process in a listener, so
that the system can distribute the incoming connections into multiple queues
and allow a smoother inter-process load balancing. Currently Linux 3.9 and
above is known for supporting this. See also "bind-process" and "nbproc".

ssl
This setting is only available when support for OpenSSL was built in. It
enables SSL deciphering on connections instantiated 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.

strict-sni
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.

tfo
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.

transparent
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.

v4v6
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 overridden by the "v6only" option.

v6only
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.

uid <uid>
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.

user <user>
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.

verify [none|optional|required]
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.

addr <ipv4|ipv6>
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

agent-check
Enable an auxiliary agent check which is run independently of a regular
health check. An agent health check is performed by making a TCP connection
to the port set by the "agent-port" parameter and reading an ASCII string.
The string is made of a series of words delimited by spaces, tabs or commas
in any order, optionally terminated by '\r' and/or '\n', each consisting of :

- An ASCII representation of a 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. Note that a zero
weight is reported on the stats page as "DRAIN" since it has the same
effect on the server (it's removed from the LB farm).

- The word "ready". This will turn the server's administrative state to the
READY mode, thus cancelling any DRAIN or MAINT state

- The word "drain". This will turn the server's administrative state to the
DRAIN mode, thus it will not accept any new connections other than those
that are accepted via persistence.

- The word "maint". This will turn the server's administrative state to the
MAINT mode, thus it will not accept any new connections at all, and health
checks will be stopped.

- The words "down", "failed", or "stopped", optionally followed by a
description string after a sharp ('#'). All of these mark the server's
operating state as DOWN, but since the word itself is reported on the stats
page, the difference allows an administrator to know if the situation was
expected or not : the service may intentionally be stopped, may appear up
but fail some validity tests, or may be seen as down (eg: missing process,
or port not responding).

- The word "up" sets back the server's operating state as UP if health checks
also report that the service is accessible.

Parameters which are not advertised by the agent are not changed. For
example, an agent might be designed to monitor CPU usage and only report a
relative weight and never interact with the operating status. Similarly, an
agent could be designed as an end-user interface with 3 radio buttons
allowing an administrator to change only the administrative state. However,
it is important to consider that only the agent may revert its own actions,
so if a server is set to DRAIN mode or to DOWN state using the agent, the
agent must implement the other equivalent actions to bring the service into
operations again.

Failure to connect to the agent is not considered an error as connectivity
is tested by the regular health check which is enabled by the "check"
parameter. Warning though, it is not a good idea to stop an agent after it
reports "down", since only an agent reporting "up" will be able to turn the
server up again. Note that the CLI on the Unix stats socket is also able to
force an agent's result in order to workaround a bogus agent if needed.

Requires the "agent-port" parameter to be set. See also the "agent-inter"
parameter.

Supported in default-server: No

agent-inter <delay>
The "agent-inter" parameter sets the interval between two agent checks
to <delay> milliseconds. If left unspecified, the delay defaults to 2000 ms.

Just as with every other time-based parameter, it may be entered in any
other explicit unit among { us, ms, s, m, h, d }. The "agent-inter"
parameter also serves as a timeout for agent checks "timeout check" is
not set. In order to reduce "resonance" effects when multiple servers are
hosted on the same hardware, the agent and 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 agent and health checks interval using the
global "spread-checks" keyword. This makes sense for instance when a lot
of backends use the same servers.

See also the "agent-check" and "agent-port" parameters.

Supported in default-server: Yes

agent-port <port>
The "agent-port" parameter sets the TCP port used for agent checks.

See also the "agent-check" and "agent-inter" parameters.

Supported in default-server: Yes

backup
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

ca-file <cafile>
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

check
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",
"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

check-send-proxy
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

check-ssl
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 checks, 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

ciphers <ciphers>
This option sets the string describing the list of cipher algorithms that is
is negotiated 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

cookie <value>
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

crl-file <crlfile>
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

crt <cert>
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

disabled
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

error-limit <count>
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".

fall <count>
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

force-sslv3
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. This option is also available on global statement
"ssl-default-server-options". See also "no-tlsv*", "no-sslv3".

Supported in default-server: No

force-tlsv10
This option enforces use of TLSv1.0 only when SSL is used to communicate with
the server. This option is also available on global statement
"ssl-default-server-options". See also "no-tlsv*", "no-sslv3".

Supported in default-server: No

force-tlsv11
This option enforces use of TLSv1.1 only when SSL is used to communicate with
the server. This option is also available on global statement
"ssl-default-server-options". See also "no-tlsv*", "no-sslv3".

Supported in default-server: No

force-tlsv12
This option enforces use of TLSv1.2 only when SSL is used to communicate with
the server. This option is also available on global statement
"ssl-default-server-options". See also "no-tlsv*", "no-sslv3".

Supported in default-server: No

id <value>
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

inter <delay>
fastinter <delay>
downinter <delay>
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), | "fastinter" if set, "inter" otherwise.
or yet unchecked. |
---------------------------------+-----------------------------------------
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 agent and 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 agent and 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: Yes

maxconn <maxconn>
The "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

maxqueue <maxqueue>
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

minconn <minconn>
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

no-sslv3
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

no-tls-tickets
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. This option
is also available on global statement "ssl-default-server-options".

Supported in default-server: No

no-tlsv10
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. This
option is also available on global statement "ssl-default-server-options".
See also "force-sslv3", "force-tlsv*".

Supported in default-server: No

no-tlsv11
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. This
option is also available on global statement "ssl-default-server-options".
See also "force-sslv3", "force-tlsv*".

Supported in default-server: No

no-tlsv12
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. This
option is also available on global statement "ssl-default-server-options".
See also "force-sslv3", "force-tlsv*".

Supported in default-server: No

non-stick
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

observe <mode>
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".

on-error <mode>
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".

on-marked-down <action>
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

on-marked-up <action>
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

port <port>
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

redir <prefix>
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

rise <count>
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

send-proxy
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

send-proxy-v2
The "send-proxy-v2" parameter enforces use of the PROXY protocol version 2
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. This setting must not be used if the
server isn't aware of this version of the protocol. See also the "send-proxy"
option of the "bind" keyword.

Supported in default-server: No

send-proxy-v2-ssl
The "send-proxy-v2-ssl" parameter enforces use of the PROXY protocol version
2 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. In addition, the SSL information extension
of the PROXY protocol is added to the PROXY protocol header. This setting
must not be used if the server isn't aware of this version of the protocol.
See also the "send-proxy-v2" option of the "bind" keyword.

Supported in default-server: No

send-proxy-v2-ssl-cn
The "send-proxy-v2-ssl" parameter enforces use of the PROXY protocol version
2 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. In addition, the SSL information extension
of the PROXY protocol, along along with the Common Name from the subject of
the client certificate (if any), is added to the PROXY protocol header. This
setting must not be used if the server isn't aware of this version of the
protocol. See also the "send-proxy-v2" option of the "bind" keyword.

Supported in default-server: No

slowstart <start_time_in_ms>
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

source <addr>[:<pl>[-<ph>]] [usesrc { <addr2>[:<port2>] | client | clientip } ]
source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | hdr_ip(<hdr>[,<occ>]) } ]
source <addr>[:<pl>[-<ph>]] [interface <name>] ...
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

ssl
This option enables SSL ciphering on outgoing connections to the server. It
is critical to verify server certificates using "verify" when using SSL to
connect to servers, otherwise the communication is prone to trivial man in
the-middle attacks rendering SSL useless. 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" option to force SSL health checks.

Supported in default-server: No

track [<proxy>/]<server>
This option enables ability to set the current state of the server by tracking
another one. It is possible to track a server which itself tracks another
server, provided that at the end of the chain, a server has health checks
enabled. 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

verify [none|required]
This setting is only available when support for OpenSSL was built in. If set
to 'none', server certificate is not verified. In the other case, The
certificate provided by the server is verified using CAs from 'ca-file'
and optional CRLs from 'crl-file'. If 'ssl_server_verify' is not specified
in global section, this is the default. On verify failure the handshake
is aborted. It is critically important to verify server certificates when
using SSL to connect to servers, otherwise the communication is prone to
trivial man-in-the-middle attacks rendering SSL totally useless.

Supported in default-server: No

verifyhost <hostname>
This setting is only available when support for OpenSSL was built in, and
only takes effect if 'verify required' is also specified. When set, the
hostnames in the subject and subjectAlternateNames of the certificate
provided by the server are checked. If none of the hostnames in the
certificate match the specified hostname, the handshake is aborted. The
hostnames in the server-provided certificate may include wildcards.

Supported in default-server: No

weight <weight>
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.

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 fetching samples
----------------------------------

Haproxy is capable of extracting data from request or response streams, from
client or server information, from tables, environmental information etc...
The action of extracting such data is called fetching a sample. Once retrieved,
these samples may be used for various purposes such as a key to a stick-table,
but most common usages consist in matching them against predefined constant
data called patterns.

7.1. ACL basics
---------------

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 :

- extract a data sample from a stream, table or the environment
- optionally apply some format conversion to the extracted sample
- apply one or multiple pattern matching methods on this sample
- perform actions only when a pattern matches the sample

The actions generally consist in blocking a request, selecting a backend, or
adding a header.

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. Optionally some
conversion operators may be applied to the sample, and they will be specified
as a comma-delimited list of keywords just after the first keyword. 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 criterion generally is the name of a sample fetch method, or one of its ACL
specific declinations. The default test method is implied by the output type of
this sample fetch method. The ACL declinations can describe alternate matching
methods of a same sample fetch method. The sample fetch methods are the only
ones supporting a conversion.

Sample fetch methods return data which can be of the following types :
- boolean
- integer (signed or unsigned)
- IPv4 or IPv6 address
- string
- data block

Converters transform any of these data into any of these. For example, some
converters might convert a string to a lower-case string while other ones
would turn a string to an IPv4 address, or apply a netmask to an IP address.
The resulting sample is of the type of the last converter applied to the list,
which defaults to the type of the sample fetch method.

Each sample or converter returns data of a specific type, specified with its
keyword in this documentation. When an ACL is declared using a standard sample
fetch method, certain types automatically involved a default matching method
which are summarized in the table below :

+---------------------+-----------------+
| Sample or converter | Default |
| output type | matching method |
+---------------------+-----------------+
| boolean | bool |
+---------------------+-----------------+
| integer | int |
+---------------------+-----------------+
| ip | ip |
+---------------------+-----------------+
| string | str |
+---------------------+-----------------+
| binary | none, use "-m" |
+---------------------+-----------------+

Note that in order to match a binary samples, it is mandatory to specify a
matching method, see below.

The ACL engine can match these types against patterns of the following types :
- boolean
- integer or integer range
- IP address / network
- string (exact, substring, suffix, prefix, subdir, domain)
- regular expression
- hex block

The following ACL flags are currently supported :

-i : ignore case during matching of all subsequent patterns.
-f : load patterns from a file.
-m : use a specific pattern matching method
-n : forbid the DNS resolutions
-M : load the file pointed by -f like a map file.
-u : force the unique id of the ACL
-- : force end of flags. Useful when a string looks like one of the flags.

The "-f" flag is followed by the name of a file from which all lines will be
read as individual values. 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 necessary 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.

The "-M" flag allows an ACL to use a map file. If this flag is set, the file is
parsed as two column file. The first column contains the patterns used by the
ACL, and the second column contain the samples. The sample can be used later by
a map. This can be useful in some rare cases where an ACL would just be used to
check for the existence of a pattern in a map before a mapping is applied.

The "-u" flag forces the unique id of the ACL. This unique id is used with the
socket interface to identify ACL and dynamically change its values. Note that a
file is always identified by its name even if an id is set.

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
as well.

The "-m" flag is used to select a specific pattern matching method on the input
sample. All ACL-specific criteria imply a pattern matching method and generally
do not need this flag. However, this flag is useful with generic sample fetch
methods to describe how they're going to be matched against the patterns. This
is required for sample fetches which return data type for which there is no
obvious matching method (eg: string or binary). When "-m" is specified and
followed by a pattern matching method name, this method is used instead of the
default one for the criterion. This makes it possible to match contents in ways
that were not initially planned, or with sample fetch methods which return a
string. The matching method also affects the way the patterns are parsed.

The "-n" flag forbids the dns resolutions. It is used with the load of ip files.
By default, if the parser cannot parse ip address it considers that the parsed
string is maybe a domain name and try dns resolution. The flag "-n" disable this
resolution. It is useful for detecting malformed ip lists. Note that if the DNS
server is not reachable, the haproxy configuration parsing may last many minutes
waiting fir the timeout. During this time no error messages are displayed. The
flag "-n" disable this behavior. Note also that during the runtime, this
function is disabled for the dynamic acl modifications.

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 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 or false does not match, all other values do match.

- "int" : match the value as an integer. It can be used with integer and
boolean samples. Boolean false is integer 0, true is integer 1.

- "ip" : match the value as an IPv4 or IPv6 address. It is compatible
with IP address samples only, so it is implied and never needed.

- "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" : exact match : match the contents against a string. This may be
used with binary or string samples.

- "sub" : substring match : check that the contents contain at least one of
the provided string patterns. This may be used with binary or
string samples.

- "reg" : regex match : match the contents against a list of regular
expressions. This may be used with binary or string samples.

- "beg" : prefix match : check that the contents begin like the provided
string patterns. This may be used with binary or string samples.

- "end" : suffix match : check that the contents end like the provided
string patterns. This may be used with binary or string samples.

- "dir" : subdir match : check that a slash-delimited portion of the
contents exactly matches one of the provided string patterns.
This may be used with binary or string samples.

- "dom" : domain match : 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.

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>

On systems where the regex library is much slower when using "-i", it is
possible to convert the sample to lowercase before matching, like this :

acl script_tag payload(0,500),lower -m reg <script>

All ACL-specific criteria imply a default matching method. Most often, these
criteria are composed by concatenating the name of the original sample fetch
method and the matching method. For example, "hdr_beg" applies the "beg" match
to samples retrieved using the "hdr" fetch method. Since all ACL-specific
criteria rely on a sample fetch method, it is always possible instead to use
the original sample fetch method and the explicit matching method using "-m".

If an alternate match is specified using "-m" on an ACL-specific criterion,
the matching method is simply applied to the underlying sample fetch method.
For example, all ACLs below are exact equivalent :

acl short_form hdr_beg(host) www.
acl alternate1 hdr_beg(host) -m beg www.
acl alternate2 hdr_dom(host) -m beg www.
acl alternate3 hdr(host) -m beg www.

The table below summarizes the compatibility matrix between sample or converter
types and the pattern types to fetch against. It indicates for each compatible
combination the name of the matching method to be used, surrounded with angle
brackets ">" and "<" when the method is the default one and will work by
default without "-m".

+-------------------------------------------------+
| Input sample type |
+----------------------+---------+---------+---------+---------+---------+
| pattern type | boolean | integer | ip | string | binary |
+----------------------+---------+---------+---------+---------+---------+
| none (presence only) | found | found | found | found | found |
+----------------------+---------+---------+---------+---------+---------+
| none (boolean value) |> bool <| bool | | bool | |
+----------------------+---------+---------+---------+---------+---------+
| integer (value) | int |> int <| int | int | |
+----------------------+---------+---------+---------+---------+---------+
| integer (length) | len | len | len | len | len |
+----------------------+---------+---------+---------+---------+---------+
| IP address | | |> ip <| ip | ip |
+----------------------+---------+---------+---------+---------+---------+
| exact string | str | str | str |> str <| str |
+----------------------+---------+---------+---------+---------+---------+
| prefix | beg | beg | beg | beg | beg |
+----------------------+---------+---------+---------+---------+---------+
| suffix | end | end | end | end | end |
+----------------------+---------+---------+---------+---------+---------+
| substring | sub | sub | sub | sub | sub |
+----------------------+---------+---------+---------+---------+---------+
| subdir | dir | dir | dir | dir | dir |
+----------------------+---------+---------+---------+---------+---------+
| domain | dom | dom | dom | dom | dom |
+----------------------+---------+---------+---------+---------+---------+
| regex | reg | reg | reg | reg | reg |
+----------------------+---------+---------+---------+---------+---------+
| hex block | | | | bin | bin |
+----------------------+---------+---------+---------+---------+---------+

7.1.1. Matching booleans
------------------------

In order to match a boolean, no value is needed and all values are ignored.
Boolean matching is used by default for all fetch methods of type "boolean".
When boolean matching is used, the fetched value is returned as-is, which means
that a boolean "true" will always match and a boolean "false" will never match.

Boolean matching may also be enforced using "-m bool" on fetch methods which
return an integer value. Then, integer value 0 is converted to the boolean
"false" and all other values are converted to "true".

7.1.2. Matching integers
------------------------

Integer matching applies by default to integer fetch methods. It can also be
enforced on boolean fetches using "-m int". In this case, "false" is converted
to the integer 0, and "true" is converted to the integer 1.

Integer matching also supports integer ranges and operators. 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

7.1.3. Matching strings
-----------------------

String matching applies to string or binary fetch methods, and exists in 6
different forms :

- exact match (-m str) : the extracted string must exactly match the
patterns ;

- substring match (-m sub) : the patterns are looked up inside the
extracted string, and the ACL matches if any of them is found inside ;

- prefix match (-m beg) : the patterns are compared with the beginning of
the extracted string, and the ACL matches if any of them matches.

- suffix match (-m end) : the patterns are compared with the end of the
extracted string, and the ACL matches if any of them matches.

- subdir match (-m sub) : the patterns are looked up inside the extracted
string, delimited with slashes ("/"), and the ACL matches if any of them
matches.

- domain match (-m dom) : the patterns are looked up inside the extracted
string, delimited with dots ("."), and the ACL matches if any of them
matches.

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 "--".

7.1.4. 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 "--".

7.1.5. Matching arbitrary data blocks
-------------------------------------

It is possible to match some extracted samples against a binary block which may
not safely be represented as a string. For this, the patterns must be passed as
a series of hexadecimal digits in an even number, when the match method is set
to binary. Each sequence of two digits will represent a byte. The hexadecimal
digits may be used upper or lower case.

Example :
# match "Hello\n" in the input stream (\x48 \x65 \x6c \x6c \x6f \x0a)
acl hello payload(0,6) -m bin 48656c6c6f0a

7.1.6. 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.

7.2. 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
the braces must be seen as independent words). 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.

7.3. Fetching samples
---------------------

Historically, sample fetch methods were only used to retrieve data to match
against patterns using ACLs. With the arrival of stick-tables, a new class of
sample fetch methods was created, most often sharing the same syntax as their
ACL counterpart. These sample fetch methods are also known as "fetches". As
of now, ACLs and fetches have converged. All ACL fetch methods have been made
available as fetch methods, and ACLs may use any sample fetch method as well.

This section details all available sample fetch methods and their output type.
Some sample fetch methods have deprecated aliases that are used to maintain
compatibility with existing configurations. They are then explicitly marked as
deprecated and should not be used in new setups.

The ACL derivatives are also indicated when available, with their respective
matching methods. These ones all have a well defined default pattern matching
method, so it is never necessary (though allowed) to pass the "-m" option to
indicate how the sample will be matched using ACLs.

As indicated in the sample type versus matching compatibility matrix above,
when using a generic sample fetch method in an ACL, the "-m" option is
mandatory unless the sample type is one of boolean, integer, IPv4 or IPv6. When
the same keyword exists as an ACL keyword and as a standard fetch method, the
ACL engine will automatically pick the ACL-only one by default.

Some of these keywords support one or multiple mandatory arguments, and one or
multiple optional arguments. These arguments are strongly typed and are checked
when the configuration is parsed so that there is no risk of running with an
incorrect argument (eg: an unresolved backend name). Fetch function arguments
are passed between parenthesis and are delimited by commas. When an argument
is optional, it will be indicated below between square brackets ('[ ]'). When
all arguments are optional, the parenthesis may be omitted.

Thus, the syntax of a standard sample fetch method is one of the following :
- name
- name(arg1)
- name(arg1,arg2)

7.3.1. Converters
-----------------

Sample fetch methods may be combined with transformations to be applied on top
of the fetched sample (also called "converters"). These combinations form what
is called "sample expressions" and the result is a "sample". Initially this
was only supported by "stick on" and "stick store-request" directives but this
has now be extended to all places where samples may be used (acls, log-format,
unique-id-format, add-header, ...).

These transformations are enumerated as a series of specific keywords after the
sample fetch method. These keywords may equally be appended immediately after
the fetch keyword's argument, delimited by a comma. These keywords can also
support some arguments (eg: a netmask) which must be passed in parenthesis.

The currently available list of transformation keywords include :

base64
Converts a binary input sample to a base64 string. It is used to log or
transfer binary content in a way that can be reliably transferred (eg:
an SSL ID can be copied in a header).

hex
Converts a binary input sample to an hex string containing two hex digits per
input byte. It is used to log or transfer hex dumps of some binary input data
in a way that can be reliably transferred (eg: an SSL ID can be copied in a
header).

http_date([<offset>])
Converts an integer supposed to contain a date since epoch to a string
representing this date in a format suitable for use in HTTP header fields. If
an offset value is specified, then it is a number of seconds that is added to
the date before the conversion is operated. This is particularly useful to
emit Date header fields, Expires values in responses when combined with a
positive offset, or Last-Modified values when the offset is negative.

ipmask(<mask>)
Apply a mask to an IPv4 address, and use the result for lookups and storage.
This can be used to make all hosts within a certain mask to share the same
table entries and as such use the same server. The mask can be passed in
dotted form (eg: 255.255.255.0) or in CIDR form (eg: 24).

language(<value>[,<default>])
Returns the value with the highest q-factor from a list as extracted from the
"accept-language" header using "req.fhdr". Values with no q-factor have a
q-factor of 1. Values with a q-factor of 0 are dropped. Only values which
belong to the list of semi-colon delimited <values> will be considered. The
argument <value> syntax is "lang[;lang[;lang[;...]]]". If no value matches the
given list and a default value is provided, it is returned. Note that language
names may have a variant after a dash ('-'). If this variant is present in the
list, it will be matched, but if it is not, only the base language is checked.
The match is case-sensitive, and the output string is always one of those
provided in arguments. The ordering of arguments is meaningless, only the
ordering of the values in the request counts, as the first value among
multiple sharing the same q-factor is used.

Example :

# this configuration switches to the backend matching a
# given language based on the request :

acl es req.fhdr(accept-language),language(es;fr;en) -m str es
acl fr req.fhdr(accept-language),language(es;fr;en) -m str fr
acl en req.fhdr(accept-language),language(es;fr;en) -m str en
use_backend spanish if es
use_backend french if fr
use_backend english if en
default_backend choose_your_language

lower
Convert a string sample to lower case. This can only be placed after a string
sample fetch function or after a transformation keyword returning a string
type. The result is of type string.

map(<map_file>[,<default_value>])
map_<match_type>(<map_file>[,<default_value>])
map_<match_type>_<output_type>(<map_file>[,<default_value>])
Search the input value from <map_file> using the <match_type> matching method,
and return the associated value converted to the type <output_type>. If the
input value cannot be found in the <map_file>, the converter returns the
<default_value>. If the <default_value> is not set, the converter fails and
acts as if no input value could be fetched. If the <match_type> is not set, it
defaults to "str". Likewise, if the <output_type> is not set, it defaults to
"str". For convenience, the "map" keyword is an alias for "map_str" and maps a
string to another string.

It is important to avoid overlapping between the keys : IP addresses and
strings are stored in trees, so the first of the finest match will be used.
Other keys are stored in lists, so the first matching occurrence will be used.

The following array contains the list of all map functions avalaible sorted by
input type, match type and output type.

The file contains one key + value per line. Lines which start with '#' are
ignored, just like empty lines. Leading tabs and spaces are stripped. The key
is then the first "word" (series of non-space/tabs characters), and the value
is what follows this series of space/tab till the end of the line excluding
trailing spaces/tabs.

Example :

# this is a comment and is ignored
2.22.246.0/23 United Kingdom \n
<-><-----------><--><------------><---->
| | | | `- trailing spaces ignored
| | | `---------- value
| | `-------------------- middle spaces ignored
| `---------------------------- key
`------------------------------------ leading spaces ignored

upper
Convert a string sample to upper case. This can only be placed after a string
sample fetch function or after a transformation keyword returning a string
type. The result is of type string.

7.3.2. Fetching samples from internal states
--------------------------------------------

A first set of sample fetch methods applies to internal information which does
not even relate to any client information. These ones are sometimes used with
"monitor-fail" directives to report an internal status to external watchers.
The sample fetch methods described in this section are usable anywhere.

always_false : boolean
Always returns the boolean "false" value. It may be used with ACLs as a
temporary replacement for another one when adjusting configurations.

always_true : boolean
Always returns the boolean "true" value. It may be used with ACLs as a
temporary replacement for another one when adjusting configurations.

avg_queue([<backend>]) : integer
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, twice the number of queued connections would be considered 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.

be_conn([<backend>]) : integer
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.

be_sess_rate([<backend>]) : integer
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.

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

connslots([<backend>]) : integer
Returns an integer value corresponding to the number of connection slots
still available in the backend, by totaling the maximum amount of
connections on all servers and the maximum queue size. This is probably only
used with ACLs.

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 fetch 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 fetch clearly does not make sense, in which case the value returned
will be -1.

date([<offset>]) : integer
Returns the current date as the epoch (number of seconds since 01/01/1970).
If an offset value is specified, then it is a number of seconds that is added
to the current date before returning the value. This is particularly useful
to compute relative dates, as both positive and negative offsets are allowed.
It is useful combined with the http_date converter.

Example :

# set an expires header to now+1 hour in every response
http-response set-header Expires %[date(3600),http_date]

env(<name>) : string
Returns a string containing the value of environment variable <name>. As a
reminder, environment variables are per-process and are sampled when the
process starts. This can be useful to pass some information to a next hop
server, or with ACLs to take specific action when the process is started a
certain way.

Examples :
# Pass the Via header to next hop with the local hostname in it
http-request add-header Via 1.1\ %[env(HOSTNAME)]

# reject cookie-less requests when the STOP environment variable is set
http-request deny if !{ cook(SESSIONID) -m found } { env(STOP) -m found }

fe_conn([<frontend>]) : integer
Returns 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 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" fetches.

fe_sess_rate([<frontend>]) : integer
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, for example when combined with other
layer 4 ACLs in order to force the clients to wait a bit for the rate to go
down below the limit. It can also be useful to add this element to logs using
a log-format directive. See also the "rate-limit sessions" directive for use
in frontends.

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

nbproc : integer
Returns an integer value corresponding to the number of processes that were
started (it equals the global "nbproc" setting). This is useful for logging
and debugging purposes.

nbsrv([<backend>]) : integer
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. This is normally 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".

proc : integer
Returns an integer value corresponding to the position of the process calling
the function, between 1 and global.nbproc. This is useful for logging and
debugging purposes.

queue([<backend>]) : integer
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. 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" fetches.

rand([<range>]) : integer
Returns a random integer value within a range of <range> possible values,
starting at zero. If the range is not specified, it defaults to 2^32, which
gives numbers between 0 and 4294967295. It can be useful to pass some values
needed to take some routing decisions for example, or just for debugging
purposes. This random must not be used for security purposes.

srv_conn([<backend>/]<server>) : integer
Returns an integer value corresponding to the number of currently established
connections on the designated server, possibly including the connection being
evaluated. If <backend> is omitted, then the server is looked up in the
current backend. It can be used to use a specific farm when one server is
full, or to inform the server about our view of the number of active
connections with it. See also the "fe_conn", "be_conn" and "queue" fetch
methods.

srv_is_up([<backend>/]<server>) : boolean
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. 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.

srv_sess_rate([<backend>/]<server>) : integer
Returns an integer corresponding to the sessions creation rate on the
designated server, in number of new sessions per second. If <backend> is
omitted, then the server is looked up in the current backend. This is mostly
used with ACLs but can make sense with logs too. 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

stopping : boolean
Returns TRUE if the process calling the function is currently stopping. This
can be useful for logging, or for relaxing certain checks or helping close
certain connections upon graceful shutdown.

table_avl([<table>]) : integer
Returns the total number of available entries in the current proxy's
stick-table or in the designated stick-table. See also table_cnt.

table_cnt([<table>]) : integer
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.

7.3.3. Fetching samples at Layer 4
----------------------------------

The layer 4 usually describes just the transport layer which in haproxy is
closest to the connection, where no content is yet made available. The fetch
methods described here are usable as low as the "tcp-request connection" rule
sets unless they require some future information. Those generally include
TCP/IP addresses and ports, as well as elements from stick-tables related to
the incoming connection. For retrieving a value from a sticky counters, the
counter number can be explicitly set as 0, 1, or 2 using the pre-defined
"sc0_", "sc1_", or "sc2_" prefix, or it can be specified as the first integer
argument when using the "sc_" prefix. An optional table may be specified with
the "sc*" form, in which case the currently tracked key will be looked up into
this alternate table instead of the table currently being tracked.

be_id : integer
Returns an integer containing the current backend's id. It can be used in
frontends with responses to check which backend processed the request.

dst : ip
This is the destination IPv4 address of the connection 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 IP 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 : integer
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. 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" fetches.

dst_port : integer
Returns an integer value corresponding to the destination TCP port of the
connection on the client side, which is the port the client connected to.
This might be used when running in transparent mode, when assigning dynamic
ports to some clients for a whole application session, to stick all users to
a same server, or to pass the destination port information to a server using
an HTTP header.

fe_id : integer
Returns an integer containing the current frontend's id. It can be used in
backends to check from which backend it was called, or to stick all users
coming via a same frontend to the same server.

sc_bytes_in_rate(<ctr>[,<table>]) : integer
sc0_bytes_in_rate([<table>]) : integer
sc1_bytes_in_rate([<table>]) : integer
sc2_bytes_in_rate([<table>]) : integer
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.

sc_bytes_out_rate(<ctr>[,<table>]) : integer
sc0_bytes_out_rate([<table>]) : integer
sc1_bytes_out_rate([<table>]) : integer
sc2_bytes_out_rate([<table>]) : integer
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.

sc_clr_gpc0(<ctr>[,<table>]) : integer
sc0_clr_gpc0([<table>]) : integer
sc1_clr_gpc0([<table>]) : integer
sc2_clr_gpc0([<table>]) : integer
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 sc0_http_req_rate gt 10
acl kill sc0_inc_gpc0 gt 5
acl save sc0_clr_gpc0 ge 0
tcp-request connection accept if !abuse save
tcp-request connection reject if abuse kill

sc_conn_cnt(<ctr>[,<table>]) : integer
sc0_conn_cnt([<table>]) : integer
sc1_conn_cnt([<table>]) : integer
sc2_conn_cnt([<table>]) : integer
Returns the cumulated number of incoming connections from currently tracked
counters. See also src_conn_cnt.

sc_conn_cur(<ctr>[,<table>]) : integer
sc0_conn_cur([<table>]) : integer
sc1_conn_cur([<table>]) : integer
sc2_conn_cur([<table>]) : integer
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.

sc_conn_rate(<ctr>[,<table>]) : integer
sc0_conn_rate([<table>]) : integer
sc1_conn_rate([<table>]) : integer
sc2_conn_rate([<table>]) : integer
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.

sc_get_gpc0(<ctr>[,<table>]) : integer
sc0_get_gpc0([<table>]) : integer
sc1_get_gpc0([<table>]) : integer
sc2_get_gpc0([<table>]) : integer
Returns the value of the first General Purpose Counter associated to the
currently tracked counters. See also src_get_gpc0 and sc/sc0/sc1/sc2_inc_gpc0.

sc_gpc0_rate(<ctr>[,<table>]) : integer
sc0_gpc0_rate([<table>]) : integer
sc1_gpc0_rate([<table>]) : integer
sc2_gpc0_rate([<table>]) : integer
Returns the average increment rate of the first General Purpose Counter
associated to the currently tracked counters. It reports the frequency
which the gpc0 counter was incremented over the configured period. See also
src_gpc0_rate, sc/sc0/sc1/sc2_get_gpc0, and sc/sc0/sc1/sc2_inc_gpc0. Note
that the "gpc0_rate" counter must be stored in the stick-table for a value to
be returned, as "gpc0" only holds the event count.

sc_http_err_cnt(<ctr>[,<table>]) : integer
sc0_http_err_cnt([<table>]) : integer
sc1_http_err_cnt([<table>]) : integer
sc2_http_err_cnt([<table>]) : integer
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.

sc_http_err_rate(<ctr>[,<table>]) : integer
sc0_http_err_rate([<table>]) : integer
sc1_http_err_rate([<table>]) : integer
sc2_http_err_rate([<table>]) : integer
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.

sc_http_req_cnt(<ctr>[,<table>]) : integer
sc0_http_req_cnt([<table>]) : integer
sc1_http_req_cnt([<table>]) : integer
sc2_http_req_cnt([<table>]) : integer
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.

sc_http_req_rate(<ctr>[,<table>]) : integer
sc0_http_req_rate([<table>]) : integer
sc1_http_req_rate([<table>]) : integer
sc2_http_req_rate([<table>]) : integer
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.

sc_inc_gpc0(<ctr>[,<table>]) : integer
sc0_inc_gpc0([<table>]) : integer
sc1_inc_gpc0([<table>]) : integer
sc2_inc_gpc0([<table>]) : integer
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 sc0_http_req_rate gt 10
acl kill sc0_inc_gpc0 gt 0
tcp-request connection reject if abuse kill

sc_kbytes_in(<ctr>[,<table>]) : integer
sc0_kbytes_in([<table>]) : integer
sc1_kbytes_in([<table>]) : integer
sc2_kbytes_in([<table>]) : integer
Returns the total amount of client-to-server data from the currently tracked
counters, measured in kilobytes. The test is currently performed on 32-bit
integers, which limits values to 4 terabytes. See also src_kbytes_in.

sc_kbytes_out(<ctr>[,<table>]) : integer
sc0_kbytes_out([<table>]) : integer
sc1_kbytes_out([<table>]) : integer
sc2_kbytes_out([<table>]) : integer
Returns the total amount of server-to-client data from the currently tracked
counters, measured in kilobytes. The test is currently performed on 32-bit
integers, which limits values to 4 terabytes. See also src_kbytes_out.

sc_sess_cnt(<ctr>[,<table>]) : integer
sc0_sess_cnt([<table>]) : integer
sc1_sess_cnt([<table>]) : integer
sc2_sess_cnt([<table>]) : integer
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.

sc_sess_rate(<ctr>[,<table>]) : integer
sc0_sess_rate([<table>]) : integer
sc1_sess_rate([<table>]) : integer
sc2_sess_rate([<table>]) : integer
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.

sc_tracked(<ctr>[,<table>]) : boolean
sc0_tracked([<table>]) : boolean
sc1_tracked([<table>]) : boolean
sc2_tracked([<table>]) : boolean
Returns true if the designated session counter is currently being tracked by
the current session. This can be useful when deciding whether or not we want
to set some values in a header passed to the server.

sc_trackers(<ctr>[,<table>]) : integer
sc0_trackers([<table>]) : integer
sc1_trackers([<table>]) : integer
sc2_trackers([<table>]) : integer
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 sc0_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.

so_id : integer
Returns an integer containing the current listening socket's id. It is useful
in frontends involving many "bind" lines, or to stick all users coming via a
same socket to the same server.

src : ip
This is the source IPv4 address of the client of the session. It is of type
IP and works on both IPv4 and IPv6 tables. On IPv6 tables, IPv4 addresses are
mapped to their IPv6 equivalent, according to RFC 4291. Note that it is the
TCP-level source address which is used, and not the address of a client
behind a proxy. However if the "accept-proxy" bind directive is used, it can
be the address of a client behind another PROXY-protocol compatible component
for all rule sets except "tcp-request connection" which sees the real address.

Example:
# add an HTTP header in requests with the originating address' country
http-request set-header X-Country %[src,map_ip(geoip.lst)]

src_bytes_in_rate([<table>]) : integer
Returns the average bytes rate from the incoming connection's source 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 sc/sc0/sc1/sc2_bytes_in_rate.

src_bytes_out_rate([<table>]) : integer
Returns the average bytes rate to the incoming connection's source 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 sc/sc0/sc1/sc2_bytes_out_rate.

src_clr_gpc0([<table>]) : integer
Clears the first General Purpose Counter associated to the incoming
connection's source 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 kill

src_conn_cnt([<table>]) : integer
Returns the cumulated number of connections initiated from the current
incoming connection's source 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 sc/sc0/sc1/sc2_conn_cnt.

src_conn_cur([<table>]) : integer
Returns the current amount of concurrent connections initiated from the
current incoming connection's source 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 sc/sc0/sc1/sc2_conn_cur.

src_conn_rate([<table>]) : integer
Returns the average connection rate from the incoming connection's source
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 sc/sc0/sc1/sc2_conn_rate.

src_get_gpc0([<table>]) : integer
Returns the value of the first General Purpose Counter associated to the
incoming connection's source 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 sc/sc0/sc1/sc2_get_gpc0 and src_inc_gpc0.

src_gpc0_rate([<table>]) : integer
Returns the average increment rate of the first General Purpose Counter
associated to the incoming connection's source address in the current proxy's
stick-table or in the designated stick-table. It reports the frequency
which the gpc0 counter was incremented over the configured period. See also
sc/sc0/sc1/sc2_gpc0_rate, src_get_gpc0, and sc/sc0/sc1/sc2_inc_gpc0. Note
that the "gpc0_rate" counter must be stored in the stick-table for a value to
be returned, as "gpc0" only holds the event count.

src_http_err_cnt([<table>]) : integer
Returns the cumulated number of HTTP errors from the incoming connection's
source address in the current proxy's stick-table or in the designated
stick-table. This includes the both request errors and 4xx error responses.
See also sc/sc0/sc1/sc2_http_err_cnt. If the address is not found, zero is
returned.

src_http_err_rate([<table>]) : integer
Returns the average rate of HTTP errors from the incoming connection's source
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 sc/sc0/sc1/sc2_http_err_rate.

src_http_req_cnt([<table>]) : integer
Returns the cumulated number of HTTP requests from the incoming connection's
source 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 sc/sc0/sc1/sc2_http_req_cnt.

src_http_req_rate([<table>]) : integer
Returns the average rate of HTTP requests from the incoming connection's
source 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 sc/sc0/sc1/sc2_http_req_rate.

src_inc_gpc0([<table>]) : integer
Increments the first General Purpose Counter associated to the incoming
connection's source 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. See also sc0/sc2/sc2_inc_gpc0.
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 kill

src_kbytes_in([<table>]) : integer
Returns the total amount of data received from the incoming connection's
source address in the current proxy's stick-table or in the designated
stick-table, measured in kilobytes. 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 sc/sc0/sc1/sc2_kbytes_in.

src_kbytes_out([<table>]) : integer
Returns the total amount of data sent to the incoming connection's source
address in the current proxy's stick-table or in the designated stick-table,
measured in kilobytes. 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 sc/sc0/sc1/sc2_kbytes_out.

src_port : integer
Returns an integer value corresponding to the TCP source port of the
connection on the client side, which is the port the client connected from.
Usage of this function is very limited as modern protocols do not care much
about source ports nowadays.

src_sess_cnt([<table>]) : integer
Returns the cumulated number of connections initiated from the incoming
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 sc/sc0/sc1/sc2_sess_cnt.

src_sess_rate([<table>]) : integer
Returns the average session rate from the incoming connection's source
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 went past the early "tcp-request" rules. If the
address is not found, zero is returned. See also sc/sc0/sc1/sc2_sess_rate.

src_updt_conn_cnt([<table>]) : integer
Creates or updates the entry associated to the incoming connection's source
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 was used to reject service abusers based on their
source address. Note: it is recommended to use the more complete "track-sc*"
actions in "tcp-request" rules 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_updt_conn_cnt gt 3 }
server local 127.0.0.1:22

srv_id : integer
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.

7.3.4. Fetching samples at Layer 5
----------------------------------

The layer 5 usually describes just the session layer which in haproxy is
closest to the session once all the connection handshakes are finished, but
when no content is yet made available. The fetch methods described here are
usable as low as the "tcp-request content" rule sets unless they require some
future information. Those generally include the results of SSL negotiations.

ssl_bc : boolean
Returns true when the back connection was made via an SSL/TLS transport
layer and is locally deciphered. This means the outgoing connection was made
other a server with the "ssl" option.

ssl_bc_alg_keysize : integer
Returns the symmetric cipher key size supported in bits when the outgoing
connection was made over an SSL/TLS transport layer.

ssl_bc_cipher : string
Returns the name of the used cipher when the outgoing connection was made
over an SSL/TLS transport layer.

ssl_bc_protocol : string
Returns the name of the used protocol when the outgoing connection was made
over an SSL/TLS transport layer.

ssl_bc_unique_id : binary
When the outgoing connection was made over an SSL/TLS transport layer,
returns the TLS unique ID as defined in RFC5929 section 3. The unique id
can be encoded to base64 using the converter: "ssl_bc_unique_id,base64".

ssl_bc_session_id : binary
Returns the SSL ID of the back connection when the outgoing connection was
made over an SSL/TLS transport layer. It is useful to log if we want to know
if session was reused or not.

ssl_bc_use_keysize : integer
Returns the symmetric cipher key size used in bits when the outgoing
connection was made over an SSL/TLS transport layer.

ssl_c_ca_err : integer
When the incoming connection was made over an SSL/TLS transport layer,
returns the ID of the first error detected during verification of the client
certificate at depth > 0, or 0 if no error was encountered during this
verification process. Please refer to your SSL library's documentation to
find the exhaustive list of error codes.

ssl_c_ca_err_depth : integer
When the incoming connection was made over an SSL/TLS transport layer,
returns the depth in the CA chain of the first error detected during the
verification of the client certificate. If no error is encountered, 0 is
returned.

ssl_c_der : binary
Returns the DER formatted certificate presented by the client when the
incoming connection was made over an SSL/TLS transport layer. When used for
an ACL, the value(s) to match against can be passed in hexadecimal form.

ssl_c_err : integer
When the incoming connection was made over an SSL/TLS transport layer,
returns the ID of the first error detected during verification at depth 0, or
0 if no error was encountered during this verification process. Please refer
to your SSL library's documentation to find the exhaustive list of error
codes.

ssl_c_i_dn([<entry>[,<occ>]]) : string
When the incoming connection was made over an SSL/TLS transport layer,
returns the full distinguished name of the issuer of the certificate
presented by the client when no <entry> is specified, or 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 value from the beginning/end of the DN.
For instance, "ssl_c_i_dn(OU,2)" the second organization unit, and
"ssl_c_i_dn(CN)" retrieves the common name.

ssl_c_key_alg : string
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 : string
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 : string
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>]]) : string
When the incoming connection was made over an SSL/TLS transport layer,
returns the full distinguished name of the subject of the certificate
presented by the client when no <entry> is specified, or 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 value from the beginning/end of the DN.
For instance, "ssl_c_s_dn(OU,2)" the second organization unit, and
"ssl_c_s_dn(CN)" retrieves the common name.

ssl_c_serial : binary
Returns the serial of the certificate presented by the client when the
incoming connection was made over an SSL/TLS transport layer. When used for
an ACL, the value(s) to match against can be passed in hexadecimal form.

ssl_c_sha1 : binary
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.
Note that the output is binary, so if you want to pass that signature to the
server, you need to encode it in hex or base64, such as in the example below:

http-request set-header X-SSL-Client-SHA1 %[ssl_c_sha1,hex]

ssl_c_sig_alg : string
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 : boolean
Returns true if current SSL session uses a client certificate even if current
connection uses SSL session resumption. See also "ssl_fc_has_crt".

ssl_c_verify : integer
Returns the verify result error ID when the incoming connection was made over
an SSL/TLS transport layer, otherwise zero if no error is encountered. Please
refer to your SSL library's documentation for an exhaustive list of error
codes.

ssl_c_version : integer
Returns the version of the certificate presented by the client when the
incoming connection was made over an SSL/TLS transport layer.

ssl_f_der : binary
Returns the DER formatted certificate presented by the frontend when the
incoming connection was made over an SSL/TLS transport layer. When used for
an ACL, the value(s) to match against can be passed in hexadecimal form.

ssl_f_i_dn([<entry>[,<occ>]]) : string
When the incoming connection was made over an SSL/TLS transport layer,
returns the full distinguished name of the issuer of the certificate
presented by the frontend when no <entry> is specified, or 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 value from the beginning/end of the DN.
For instance, "ssl_f_i_dn(OU,2)" the second organization unit, and
"ssl_f_i_dn(CN)" retrieves the common name.

ssl_f_key_alg : string
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 : string
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 : string
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>]]) : string
When the incoming connection was made over an SSL/TLS transport layer,
returns the full distinguished name of the subject of the certificate
presented by the frontend when no <entry> is specified, or 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 value from the beginning/end of the DN.
For instance, "ssl_f_s_dn(OU,2)" the second organization unit, and
"ssl_f_s_dn(CN)" retrieves the common name.

ssl_f_serial : binary
Returns the serial of the certificate presented by the frontend when the
incoming connection was made over an SSL/TLS transport layer. When used for
an ACL, the value(s) to match against can be passed in hexadecimal form.

ssl_f_sha1 : binary
Returns the SHA-1 fingerprint of the certificate presented by the frontend
when the incoming connection was made over an SSL/TLS transport layer. This
can be used to know which certificate was chosen using SNI.

ssl_f_sig_alg : string
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 : integer
Returns the version of the certificate presented by the frontend when the
incoming connection was made over an SSL/TLS transport layer.

ssl_fc : boolean
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.

Example :
# This passes "X-Proto: https" to servers when client connects over SSL
listen http-https
bind :80
bind :443 ssl crt /etc/haproxy.pem
http-request add-header X-Proto https if { ssl_fc }

ssl_fc_alg_keysize : integer
Returns the symmetric cipher key size supported in bits when the incoming
connection was made over an SSL/TLS transport layer.

ssl_fc_alpn : string
This extracts the Application Layer Protocol Negotiation field from an
incoming connection made via a 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 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. See also "ssl_fc_npn".

ssl_fc_cipher : string
Returns the name of the used cipher when the incoming connection was made
over an SSL/TLS transport layer.

ssl_fc_has_crt : boolean
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.

ssl_fc_has_sni : boolean
This checks for the presence of a Server Name Indication TLS extension (SNI)
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).

ssl_fc_npn : string
This extracts the Next Protocol Negotiation field from an incoming connection
made via a 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 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.

ssl_fc_protocol : string
Returns the name of the used protocol when the incoming connection was made
over an SSL/TLS transport layer.

ssl_fc_unique_id : binary
When the incoming connection was made over an SSL/TLS transport layer,
returns the TLS unique ID as defined in RFC5929 section 3. The unique id
can be encoded to base64 using the converter: "ssl_bc_unique_id,base64".

ssl_fc_session_id : binary
Returns the SSL ID of the front connection when the incoming connection was
made over an SSL/TLS transport layer. It is useful to stick a given client to
a server. It is important to note that some browsers refresh their session ID
every few minutes.

ssl_fc_sni : string
This extracts the Server Name Indication TLS extension (SNI) field from an
incoming connection made via an SSL/TLS transport layer and locally
deciphered by haproxy. The result (when present) typically is a string
matching the HTTPS host name (253 chars or less). The SSL library must have
been built with support for TLS extensions enabled (check haproxy -vv).

This fetch 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_reg" below. This
requires that the SSL library is build with support for TLS extensions
enabled (check haproxy -vv).

ACL derivatives :
ssl_fc_sni_end : suffix match
ssl_fc_sni_reg : regex match

ssl_fc_use_keysize : integer
Returns the symmetric cipher key size used in bits when the incoming
connection was made over an SSL/TLS transport layer.

7.3.5. Fetching samples from buffer contents (Layer 6)
------------------------------------------------------

Fetching samples from buffer contents is a bit different from the previous
sample fetches above because the sampled data are ephemeral. These data can
only be used when they're available and will be lost when they're forwarded.
For this reason, samples fetched from buffer contents during a request cannot
be used in a response for example. Even while the data are being fetched, they
can change. Sometimes it is necessary to set some delays or combine multiple
sample fetch methods to ensure that the expected data are complete and usable,
for example through TCP request content inspection. Please see the "tcp-request
content" keyword for more detailed information on the subject.

payload(<offset>,<length>) : binary (deprecated)
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>]) : binary (deprecated)
This is an alias for "req.payload_lv" when used in the context of a request
(eg: "stick on", "stick match"), and for "res.payload_lv" when used in the
context of a response such as in "stick store response".

req.len : integer
req_len : integer (deprecated)
Returns an integer value corresponding to the number of bytes present in the
request buffer. This is mostly used in ACL. 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.

req.payload(<offset>,<length>) : binary
This extracts a binary block of <length> bytes and starting at byte <offset>
in the request buffer. As a special case, if the <length> argument is zero,
the the whole buffer from <offset> to the end is extracted. This can be used
with ACLs in order to check for the presence of some content in a buffer at
any location.

ACL alternatives :
payload(<offset>,<length>) : hex binary match

req.payload_lv(<offset1>,<length>[,<offset2>]) : binary
This extracts a binary 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 buffer. The <offset2> parameter also supports relative offsets if
prepended with a '+' or '-' sign.

ACL alternatives :
payload_lv(<offset1>,<length>[,<offset2>]) : hex binary match

Example : please consult the example from the "stick store-response" keyword.

req.proto_http : boolean
req_proto_http : boolean (deprecated)
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. The test does not match until the
request is complete, failed or timed out. This test may be used to report the
protocol in TCP logs, but the biggest use is to block TCP request analysis
until a complete HTTP request is present in the buffer, for example to track
a header.

Example:
# track request counts per "base" (concatenation of Host+URL)
tcp-request inspect-delay 10s
tcp-request content reject if !HTTP
tcp-request content track-sc0 base table req-rate

req.rdp_cookie([<name>]) : string
rdp_cookie([<name>]) : string (deprecated)
When the request buffer looks like the RDP protocol, extracts the RDP cookie
<name>, or any cookie if unspecified. The parser only checks for the first
cookie, as illustrated in the RDP protocol specification. The cookie name is
case insensitive. Generally the "MSTS" cookie name will be used, as it can
contain the user name of the client connecting to the server if properly
configured on the client. The "MSTSHASH" cookie is often used as well for
session stickiness to servers.

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".

ACL derivatives :
req_rdp_cookie([<name>]) : exact string match

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

See also : "balance rdp-cookie", "persist rdp-cookie", "tcp-request" and the
"req_rdp_cookie" ACL.

req.rdp_cookie_cnt([name]) : integer
rdp_cookie_cnt([name]) : integer (deprecated)
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.

ACL derivatives :
req_rdp_cookie_cnt([<name>]) : integer match

req.ssl_hello_type : integer
req_ssl_hello_type : integer (deprecated)
Returns an integer value containing the type of the SSL hello message found
in the request buffer if the buffer contains data that parse as a complete
SSL (v3 or superior) client hello message. 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 to detect presence of an SSL hello message
that is supposed to contain an SSL session ID usable for stickiness.

req.ssl_sni : string
req_ssl_sni : string (deprecated)
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 if the buffer
contains data that parse as a complete SSL (v3 or superior) client hello
message. 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. 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. See also
"ssl_fc_sni".

ACL derivatives :
req_ssl_sni : exact string match

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

res.ssl_hello_type : integer
rep_ssl_hello_type : integer (deprecated)
Returns an integer value containing the type of the SSL hello message found
in the response buffer if the buffer contains data that parses as a complete
SSL (v3 or superior) hello message. 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 to detect presence of an SSL hello message
that is supposed to contain an SSL session ID usable for stickiness.

req.ssl_ver : integer
req_ssl_ver : integer (deprecated)
Returns an integer value containing the version of the SSL/TLS protocol of a
stream present in the request buffer. Both SSLv2 hello messages and SSLv3
messages are supported. TLSv1 is announced as SSL version 3.1. 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. The ACL version of the test
matches against a decimal notation in the form MAJOR.MINOR (eg: 3.1). This
fetch is mostly used in ACL.

ACL derivatives :
req_ssl_ver : decimal match

res.len : integer
Returns an integer value corresponding to the number of bytes present in the
response buffer. This is mostly used in ACL. 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 response
content inspection.

res.payload(<offset>,<length>) : binary
This extracts a binary block of <length> bytes and starting at byte <offset>
in the response buffer. As a special case, if the <length> argument is zero,
the the whole buffer from <offset> to the end is extracted. This can be used
with ACLs in order to check for the presence of some content in a buffer at
any location.

res.payload_lv(<offset1>,<length>[,<offset2>]) : binary
This extracts a binary block whose size is specified at <offset1> for <length>
bytes, and which starts at <offset2> if specified or just after the length in
the response buffer. The <offset2> parameter also supports relative offsets
if prepended with a '+' or '-' sign.

Example : please consult the example from the "stick store-response" keyword.

wait_end : boolean
This fetch either returns true when the inspection period is over, or does
not fetch. It is only used in ACLs, 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

7.3.6. Fetching HTTP samples (Layer 7)
--------------------------------------

It is possible to fetch samples from HTTP contents, requests and responses.
This application layer is also called layer 7. It is only possible to fetch the
data in this section when a full HTTP request or response has been parsed from
its respective request or response buffer. This is always the case with all
HTTP specific rules and for sections running with "mode http". When using TCP
content inspection, it may be necessary to support an inspection delay in order
to let the request or response come in first. These fetches may require a bit
more CPU resources than the layer 4 ones, but not much since the request and
response are indexed.

base : string
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. With ACLs it can allow simple content
switching rules involving the host and the path at the same time, such as
"www.example.com/favicon.ico". See also "path" and "uri".

ACL derivatives :
base : exact string match
base_beg : prefix match
base_dir : subdir match
base_dom : domain match
base_end : suffix match
base_len : length match
base_reg : regex match
base_sub : substring match

base32 : integer
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 : binary
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.

capture.req.hdr(<idx>) : string
This extracts the content of the header captured by the "capture request
header", idx is the position of the capture keyword in the configuration.
The first entry is an index of 0. See also: "capture request header".

capture.req.method : string
This extracts the METHOD of an HTTP request. It can be used in both request
and response. Unlike "method", it can be used in both request and response
because it's allocated.

capture.req.uri : string
This extracts the request's URI, which starts at the first slash and ends
before the first space in the request (without the host part). Unlike "path"
and "url", it can be used in both request and response because it's
allocated.

capture.req.ver : string
This extracts the request's HTTP version and returns either "HTTP/1.0" or
"HTTP/1.1". Unlike "req.ver", it can be used in both request, response, and
logs because it relies on a persistent flag.

capture.res.hdr(<idx>) : string
This extracts the content of the header captured by the "capture response
header", idx is the position of the capture keyword in the configuration.
The first entry is an index of 0.
See also: "capture response header"

capture.res.ver : string
This extracts the response's HTTP version and returns either "HTTP/1.0" or
"HTTP/1.1". Unlike "res.ver", it can be used in logs because it relies on a
persistent flag.

req.cook([<name>]) : string
cook([<name>]) : string (deprecated)
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. When used with ACLs, all
matching cookies are evaluated. Spaces around the name and the value are
ignored as requested by the Cookie header specification (RFC6265). The cookie
name is case-sensitive. Empty cookies are valid, so an empty cookie may very
well return an empty value if it is present. Use the "found" match to detect
presence. Use the res.cook() variant for response cookies sent by the server.

ACL derivatives :
cook([<name>]) : exact string match
cook_beg([<name>]) : prefix match
cook_dir([<name>]) : subdir match
cook_dom([<name>]) : domain match
cook_end([<name>]) : suffix match
cook_len([<name>]) : length match
cook_reg([<name>]) : regex match
cook_sub([<name>]) : substring match

req.cook_cnt([<name>]) : integer
cook_cnt([<name>]) : integer (deprecated)
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>]) : integer
cook_val([<name>]) : integer (deprecated)
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. When
used in ACLs, all matching names are iterated over until a value matches.

cookie([<name>]) : string (deprecated)
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. This fetch should not be used
anymore and should be replaced by req.cook() or res.cook() instead as it
ambiguously uses the direction based on the context where it is used.
See also : "appsession".

hdr([<name>[,<occ>]]) : string
This is equivalent to req.hdr() when used on requests, and to res.hdr() when
used on responses. Please refer to these respective fetches for more details.
In case of doubt about the fetch direction, please use the explicit ones.
Note that contrary to the hdr() sample fetch method, the hdr_* ACL keywords
unambiguously apply to the request headers.

req.fhdr(<name>[,<occ>]) : string
This extracts the last occurrence of header <name> in an HTTP request. When
used from an ACL, all occurrences are iterated over until a match is found.
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. It differs from req.hdr() in that any commas
present in the value are returned and are not used as delimiters. This is
sometimes useful with headers such as User-Agent.

req.fhdr_cnt([<name>]) : integer
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. Contrary to its req.hdr_cnt() cousin, this function returns
the number of full line headers and does not stop on commas.

req.hdr([<name>[,<occ>]]) : string
This extracts the last occurrence of header <name> in an HTTP request. When
used from an ACL, all occurrences are iterated over until a match is found.
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. The function
considers any comma as a delimiter for distinct values. If full-line headers
are desired instead, use req.fhdr(). Please carefully check RFC2616 to know
how certain headers are supposed to be parsed. Also, some of them are case
insensitive (eg: Connection).

ACL derivatives :
hdr([<name>[,<occ>]]) : exact string match
hdr_beg([<name>[,<occ>]]) : prefix match
hdr_dir([<name>[,<occ>]]) : subdir match
hdr_dom([<name>[,<occ>]]) : domain match
hdr_end([<name>[,<occ>]]) : suffix match
hdr_len([<name>[,<occ>]]) : length match
hdr_reg([<name>[,<occ>]]) : regex match
hdr_sub([<name>[,<occ>]]) : substring match

req.hdr_cnt([<name>]) : integer
hdr_cnt([<header>]) : integer (deprecated)
Returns an integer value representing the number of occurrences of request
header field name <name>, or the total number of header field values if
<name> is not specified. It is important to remember that one header line may
count as several headers if it has several values. The function considers any
comma as a delimiter for distinct values. If full-line headers are desired
instead, req.fhdr_cnt() should be used instead. With ACLs, it can be 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 "req.hdr" for more information on header matching.

req.hdr_ip([<name>[,<occ>]]) : ip
hdr_ip([<name>[,<occ>]]) : ip (deprecated)
This extracts the last occurrence of header <name> in an HTTP request,
converts it to an IPv4 or IPv6 address and returns this address. When used
with ACLs, all occurrences are checked, and if <name> is omitted, every value
of every header is checked. 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 and X-Client-IP headers.

req.hdr_val([<name>[,<occ>]]) : integer
hdr_val([<name>[,<occ>]]) : integer (deprecated)
This extracts the last occurrence of header <name> in an HTTP request, and
converts it to an integer value. When used with ACLs, all occurrences are
checked, and if <name> is omitted, every value of every header is checked.
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.

http_auth(<userlist>) : boolean
Returns a boolean indicating whether the authentication data received from
the client match a username & password stored in the specified userlist. This
fetch function is not really useful outside of ACLs. Currently only http
basic auth is supported.

http_auth_group(<userlist>) : string
Returns a string corresponding to the user name found in the authentication
data received from the client if both the user name and password are valid
according to the specified userlist. The main purpose is to use it in ACLs
where it is then checked whether the user belongs to any group within a list.
This fetch function is not really useful outside of ACLs. Currently only http
basic auth is supported.

ACL derivatives :
http_auth_group(<userlist>) : group ...
Returns true when the user extracted from the request and whose password is
valid according to the specified userlist belongs to at least one of the
groups.

http_first_req : boolean
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 : integer + string
Returns an integer value corresponding 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 as a sample, this is only meant to
be used from ACLs, which transparently convert methods from patterns to these
integer + string values. Some predefined ACL already check for most common
methods.

ACL derivatives :
method : case insensitive method match

Example :
# only accept GET and HEAD requests
acl valid_method method GET HEAD
http-request deny if ! valid_method

path : string
This extracts the request's URL path, which starts at the first slash and
ends before the question mark (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. With ACLs, it's typically
used to match exact file names (eg: "/login.php"), or directory parts using
the derivative forms. See also the "url" and "base" fetch methods.

ACL derivatives :
path : exact string match
path_beg : prefix match
path_dir : subdir match
path_dom : domain match
path_end : suffix match
path_len : length match
path_reg : regex match
path_sub : substring match

req.ver : string
req_ver : string (deprecated)
Returns the version string from the HTTP request, for example "1.1". This can
be useful for logs, but is mostly there for ACL. Some predefined ACL already
check for versions 1.0 and 1.1.

ACL derivatives :
req_ver : exact string match

res.comp : boolean
Returns the boolean "true" value if the response has been compressed by
HAProxy, otherwise returns boolean "false". This may be used to add
information in the logs.

res.comp_algo : string
Returns a string containing the name of the algorithm used if the response
was compressed by HAProxy, for example : "deflate". This may be used to add
some information in the logs.

res.cook([<name>]) : string
scook([<name>]) : string (deprecated)
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.

ACL derivatives :
scook([<name>] : exact string match

res.cook_cnt([<name>]) : integer
scook_cnt([<name>]) : integer (deprecated)
Returns an integer value representing the number of occurrences of the cookie
<name> in the response, or all cookies if <name> is not specified. This is
mostly useful when combined with ACLs to detect suspicious responses.

res.cook_val([<name>]) : integer
scook_val([<name>]) : integer (deprecated)
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.fhdr([<name>[,<occ>]]) : string
This extracts the last occurrence of header <name> in an HTTP response, or of
the last header if no <name> is specified. 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. It
differs from res.hdr() in that any commas present in the value are returned
and are not used as delimiters. If this is not desired, the res.hdr() fetch
should be used instead. This is sometimes useful with headers such as Date or
Expires.

res.fhdr_cnt([<name>]) : integer
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. Contrary to its res.hdr_cnt() cousin, this function returns
the number of full line headers and does not stop on commas. If this is not
desired, the res.hdr_cnt() fetch should be used instead.

res.hdr([<name>[,<occ>]]) : string
shdr([<name>[,<occ>]]) : string (deprecated)
This extracts the last occurrence of header <name> in an HTTP response, or of
the last header if no <name> is specified. 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. The function considers
any comma as a delimiter for distinct values. If this is not desired, the
res.fhdr() fetch should be used instead.

ACL derivatives :
shdr([<name>[,<occ>]]) : exact string match
shdr_beg([<name>[,<occ>]]) : prefix match
shdr_dir([<name>[,<occ>]]) : subdir match
shdr_dom([<name>[,<occ>]]) : domain match
shdr_end([<name>[,<occ>]]) : suffix match
shdr_len([<name>[,<occ>]]) : length match
shdr_reg([<name>[,<occ>]]) : regex match
shdr_sub([<name>[,<occ>]]) : substring match

res.hdr_cnt([<name>]) : integer
shdr_cnt([<name>]) : integer (deprecated)
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. The function considers any comma as a delimiter for distinct
values. If this is not desired, the res.fhdr_cnt() fetch should be used
instead.

res.hdr_ip([<name>[,<occ>]]) : ip
shdr_ip([<name>[,<occ>]]) : ip (deprecated)
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>]]) : integer
shdr_val([<name>[,<occ>]]) : integer (deprecated)
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.ver : string
resp_ver : string (deprecated)
Returns the version string from the HTTP response, for example "1.1". This
can be useful for logs, but is mostly there for ACL.

ACL derivatives :
resp_ver : exact string match

set-cookie([<name>]) : string (deprecated)
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.

This fetch function is deprecated and has been superseded by the "res.cook"
fetch. This keyword will disappear soon.

Arvim

The wind can blow away the spring, but it couldn't go spring, the seeds of failure can be dim yesterday's efforts, but could not prevent the arrival of the brilliant tomorrow.

Haproxy Configure File

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