doc/configuration.txt

                         ----------------------
                                HAProxy
                          Configuration Manual
                         ----------------------
                              version 2.1
                             willy tarreau
                              2019/11/15


This document covers the configuration language as implemented in the version
specified above. It does not provide any hints, examples, or advice. For such
documentation, please refer to the Reference Manual or the Architecture Manual.
The summary below is meant to help you find sections by name and navigate
through the document.

Note to documentation contributors :
    This document is formatted with 80 columns per line, with even number of
    spaces for indentation and without tabs. Please follow these rules strictly
    so that it remains easily printable everywhere. If a line needs to be
    printed verbatim and does not fit, please end each line with a backslash
    ('\') and continue on next line, indented by two characters. It is also
    sometimes useful to prefix all output lines (logs, console outputs) with 3
    closing angle brackets ('>>>') in order to emphasize the difference between
    inputs and outputs when they may be ambiguous. If you add sections,
    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.      Quoting and escaping
2.3.      Environment variables
2.4.      Time format
2.5.      Examples

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

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
5.3.      Server DNS resolution
5.3.1.      Global overview
5.3.2.      The resolvers section

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

6.    Cache
6.1.      Limitation
6.2.      Setup
6.2.1.        Cache section
6.2.2.        Proxy section

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.    Supported filters
9.1.      Trace
9.2.      HTTP compression
9.3.      Stream Processing Offload Engine (SPOE)
9.4.      Cache
9.5.      fcgi-app

10.   FastCGI applications
10.1.     Setup
10.1.1.       Fcgi-app section
10.1.2.       Proxy section
10.1.3.       Example
10.2.     Default parameters
10.3.     Limitations


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 through 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.

Another 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.

The next improvement is the multiplexed mode, as implemented in HTTP/2. This
time, each transaction is assigned a single stream identifier, and all streams
are multiplexed over an existing connection. Many requests can be sent in
parallel by the client, and responses can arrive in any order since they also
carry the stream identifier.

By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and
leaves the connection idle on both sides between the end of a response and the
start of a new request. When it receives HTTP/2 connections from a client, it
processes all the requests in parallel and leaves the connection idling,
waiting for new requests, just as if it was a keep-alive HTTP connection.

HAProxy supports 4 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 (deprecated).
  - server close  : the server-facing connection is closed after the response.
  - close         : the connection is actively closed after end of response.

For HTTP/2, the connection mode resembles more the "server close" mode : given
the independence of all streams, there is currently no place to hook the idle
server connection after a response, so it is closed after the response. HTTP/2
is only supported for incoming connections, not on connections going to
servers.


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.

HTTP/2 doesn't convey a version information with the request, so the version is
assumed to be the same as the one of the underlying protocol (i.e. "HTTP/2").
However, haproxy natively processes HTTP/1.x requests and headers, so requests
received over an HTTP/2 connection are transcoded to HTTP/1.1 before being
processed. This explains why they still appear as "HTTP/1.1" in haproxy's logs
as well as in server logs.


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 misconception, header names are not case-sensitive, and
their values are not either if they refer to other header names (such as the
"Connection:" header). In HTTP/2, header names are always sent in lower case,
as can be seen when running in debug mode.

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 RFC7231, 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 (e.g. 100, 101)
 - 2xx = OK, content is following   (e.g. 200, 206)
 - 3xx = OK, no content following   (e.g. 302, 304)
 - 4xx = error caused by the client (e.g. 401, 403, 404)
 - 5xx = error caused by the server (e.g. 500, 502, 503)

Please refer to RFC7231 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 "http-request deny" rule
   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 "http-response deny" rule 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.


2.2. Quoting and escaping
-------------------------

HAProxy's configuration introduces a quoting and escaping system similar to
many programming languages. The configuration file supports 3 types: escaping
with a backslash, weak quoting with double quotes, and strong quoting with
single quotes.

If spaces have to be entered in strings, then they must be escaped by preceding
them by a backslash ('\') or by quoting them. Backslashes also have to be
escaped by doubling or strong quoting them.

Escaping is achieved by preceding a special character by a backslash ('\'):

  \    to mark a space and differentiate it from a delimiter
  \#   to mark a hash and differentiate it from a comment
  \\   to use a backslash
  \'   to use a single quote and differentiate it from strong quoting
  \"   to use a double quote and differentiate it from weak quoting

Weak quoting is achieved by using double quotes (""). Weak quoting prevents
the interpretation of:

       space as a parameter separator
  '    single quote as a strong quoting delimiter
  #    hash as a comment start

Weak quoting permits the interpretation of variables, if you want to use a non
-interpreted dollar within a double quoted string, you should escape it with a
backslash ("\$"), it does not work outside weak quoting.

Interpretation of escaping and special characters are not prevented by weak
quoting.

Strong quoting is achieved by using single quotes (''). Inside single quotes,
nothing is interpreted, it's the efficient way to quote regexes.

Quoted and escaped strings are replaced in memory by their interpreted
equivalent, it allows you to perform concatenation.

  Example:
      # those are equivalents:
      log-format %{+Q}o\ %t\ %s\ %{-Q}r
      log-format "%{+Q}o %t %s %{-Q}r"
      log-format '%{+Q}o %t %s %{-Q}r'
      log-format "%{+Q}o %t"' %s %{-Q}r'
      log-format "%{+Q}o %t"' %s'\ %{-Q}r

      # those are equivalents:
      reqrep "^([^\ :]*)\ /static/(.*)"     \1\ /\2
      reqrep "^([^ :]*)\ /static/(.*)"     '\1 /\2'
      reqrep "^([^ :]*)\ /static/(.*)"     "\1 /\2"
      reqrep "^([^ :]*)\ /static/(.*)"     "\1\ /\2"


2.3. Environment variables
--------------------------

HAProxy's configuration supports environment variables. Those variables are
interpreted only within double quotes. Variables are expanded during the
configuration parsing. Variable names must be preceded by a dollar ("$") and
optionally enclosed with braces ("{}") similarly to what is done in Bourne
shell. Variable names can contain alphanumerical characters or the character
underscore ("_") but should not start with a digit.

  Example:

      bind "fd@${FD_APP1}"

      log "${LOCAL_SYSLOG}:514" local0 notice   # send to local server

      user "$HAPROXY_USER"

Some variables are defined by HAProxy, they can be used in the configuration
file, or could be inherited by a program (See 3.7. Programs):

* HAPROXY_LOCALPEER: defined at the startup of the process which contains the
  name of the local peer. (See "-L" in the management guide.)

* HAPROXY_CFGFILES: list of the configuration files loaded by HAProxy,
  separated by semicolons. Can be useful in the case you specified a
  directory.

* HAPROXY_MWORKER: In master-worker mode, this variable is set to 1.

* HAPROXY_CLI: configured listeners addresses of the stats socket for every
  processes, separated by semicolons.

* HAPROXY_MASTER_CLI: In master-worker mode, listeners addresses of the master
  CLI, separated by semicolons.

See also "external-check command" for other variables.

2.4. 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


2.5. 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
   - cpu-map
   - daemon
   - description
   - deviceatlas-json-file
   - deviceatlas-log-level
   - deviceatlas-separator
   - deviceatlas-properties-cookie
   - external-check
   - gid
   - group
   - hard-stop-after
   - h1-case-adjust
   - h1-case-adjust-file
   - log
   - log-tag
   - log-send-hostname
   - lua-load
   - mworker-max-reloads
   - nbproc
   - nbthread
   - node
   - pidfile
   - presetenv
   - resetenv
   - uid
   - ulimit-n
   - user
   - set-dumpable
   - setenv
   - stats
   - ssl-default-bind-ciphers
   - ssl-default-bind-ciphersuites
   - ssl-default-bind-options
   - ssl-default-server-ciphers
   - ssl-default-server-ciphersuites
   - ssl-default-server-options
   - ssl-dh-param-file
   - ssl-server-verify
   - unix-bind
   - unsetenv
   - 51degrees-data-file
   - 51degrees-property-name-list
   - 51degrees-property-separator
   - 51degrees-cache-size
   - wurfl-data-file
   - wurfl-information-list
   - wurfl-information-list-separator
   - wurfl-cache-size
   - strict-limits

 * Performance tuning
   - busy-polling
   - max-spread-checks
   - maxconn
   - maxconnrate
   - maxcomprate
   - maxcompcpuusage
   - maxpipes
   - maxsessrate
   - maxsslconn
   - maxsslrate
   - maxzlibmem
   - noepoll
   - nokqueue
   - noevports
   - nopoll
   - nosplice
   - nogetaddrinfo
   - noreuseport
   - profiling.tasks
   - spread-checks
   - server-state-base
   - server-state-file
   - ssl-engine
   - ssl-mode-async
   - tune.buffers.limit
   - tune.buffers.reserve
   - tune.bufsize
   - tune.chksize
   - tune.comp.maxlevel
   - tune.h2.header-table-size
   - tune.h2.initial-window-size
   - tune.h2.max-concurrent-streams
   - tune.http.cookielen
   - tune.http.logurilen
   - tune.http.maxhdr
   - tune.idletimer
   - tune.lua.forced-yield
   - tune.lua.maxmem
   - tune.lua.session-timeout
   - tune.lua.task-timeout
   - tune.lua.service-timeout
   - tune.maxaccept
   - tune.maxpollevents
   - tune.maxrewrite
   - tune.pattern.cache-size
   - tune.pipesize
   - tune.rcvbuf.client
   - tune.rcvbuf.server
   - tune.recv_enough
   - tune.runqueue-depth
   - 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.ssl.ssl-ctx-cache-size
   - tune.ssl.capture-cipherlist-size
   - tune.vars.global-max-size
   - tune.vars.proc-max-size
   - tune.vars.reqres-max-size
   - tune.vars.sess-max-size
   - tune.vars.txn-max-size
   - 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 non-writable to anyone.

cpu-map [auto:]<process-set>[/<thread-set>] <cpu-set>...
  On Linux 2.6 and above, it is possible to bind a process or a thread to a
  specific CPU set. This means that the process or the thread will never run on
  other CPUs. The "cpu-map" directive specifies CPU sets for process or thread
  sets. The first argument is a process set, eventually followed by a thread
  set. These sets have the format

      all | odd | even | number[-[number]]

  <number>> must be a number between 1 and 32 or 64, depending on the machine's
  word size. Any process IDs above nbproc and any thread IDs above nbthread are
  ignored. It is possible to specify a range with two such number delimited by
  a dash ('-'). It also 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 or threads 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. A thread will be bound on the intersection of its mapping and the
  one of the process on which it is attached. If the intersection is null, no
  specific binding will be set for the thread.

  Ranges can be partially defined. The higher bound can be omitted. In such
  case, it is replaced by the corresponding maximum value, 32 or 64 depending
  on the machine's word size.

  The prefix "auto:" can be added before the process set to let HAProxy
  automatically bind a process or a thread to a CPU by incrementing
  process/thread and CPU sets. To be valid, both sets must have the same
  size. No matter the declaration order of the CPU sets, it will be bound from
  the lowest to the highest bound. Having a process and a thread range with the
  "auto:" prefix is not supported. Only one range is supported, the other one
  must be a fixed number.

  Examples:
      cpu-map 1-4 0-3   # bind processes 1 to 4 on the first 4 CPUs

      cpu-map 1/all 0-3 # bind all threads of the first process on the
                        # first 4 CPUs

      cpu-map 1- 0-     # will be replaced by "cpu-map 1-64 0-63"
                        # or "cpu-map 1-32 0-31" depending on the machine's
                        # word size.

      # all these lines bind the process 1 to the cpu 0, the process 2 to cpu 1
      # and so on.
      cpu-map auto:1-4   0-3
      cpu-map auto:1-4   0-1 2-3
      cpu-map auto:1-4   3 2 1 0

      # all these lines bind the thread 1 to the cpu 0, the thread 2 to cpu 1
      # and so on.
      cpu-map auto:1/1-4   0-3
      cpu-map auto:1/1-4   0-1 2-3
      cpu-map auto:1/1-4   3 2 1 0

      # bind each process to exactly one CPU using all/odd/even keyword
      cpu-map auto:all   0-63
      cpu-map auto:even  0-31
      cpu-map auto:odd   32-63

      # invalid cpu-map because process and CPU sets have different sizes.
      cpu-map auto:1-4   0    # invalid
      cpu-map auto:1     0-3  # invalid

      # invalid cpu-map because automatic binding is used with a process range
      # and a thread range.
      cpu-map auto:all/all   0 # invalid
      cpu-map auto:all/1-4   0 # invalid
      cpu-map auto:1-4/all   0 # invalid

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. This option is ignored in
  systemd mode.

deviceatlas-json-file <path>
  Sets the path of the DeviceAtlas JSON data file to be loaded by the API.
  The path must be a valid JSON data file and accessible by HAProxy process.

deviceatlas-log-level <value>
  Sets the level of information returned by the API. This directive is
  optional and set to 0 by default if not set.

deviceatlas-separator <char>
  Sets the character separator for the API properties results. This directive
  is optional and set to | by default if not set.

deviceatlas-properties-cookie <name>
  Sets the client cookie's name used for the detection if the DeviceAtlas
  Client-side component was used during the request. This directive is optional
  and set to DAPROPS by default if not set.

external-check
  Allows the use of an external agent to perform health checks.
  This is disabled by default as a security precaution.
  See "option external-check".

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".

hard-stop-after <time>
  Defines the maximum time allowed to perform a clean soft-stop.

  Arguments :
    <time>  is the maximum time (by default in milliseconds) for which the
            instance will remain alive when a soft-stop is received via the
            SIGUSR1 signal.

  This may be used to ensure that the instance will quit even if connections
  remain opened during a soft-stop (for example with long timeouts for a proxy
  in tcp mode). It applies both in TCP and HTTP mode.

  Example:
    global
      hard-stop-after 30s

h1-case-adjust <from> <to>
  Defines the case adjustment to apply, when enabled, to the header name
  <from>, to change it to <to> before sending it to HTTP/1 clients or
  servers. <from> must be in lower case, and <from> and <to> must not differ
  except for their case. It may be repeated if several header names need to be
  ajusted. Duplicate entries are not allowed. If a lot of header names have to
  be adjusted, it might be more convenient to use "h1-case-adjust-file".
  Please note that no transformation will be applied unless "option
  h1-case-adjust-bogus-client" or "option h1-case-adjust-bogus-server" is
  specified in a proxy.

  There is no standard case for header names because, as stated in RFC7230,
  they are case-insensitive. So applications must handle them in a case-
  insensitive manner. But some bogus applications violate the standards and
  erroneously rely on the cases most commonly used by browsers. This problem
  becomes critical with HTTP/2 because all header names must be exchanged in
  lower case, and HAProxy follows the same convention. All header names are
  sent in lower case to clients and servers, regardless of the HTTP version.

  Applications which fail to properly process requests or responses may require
  to temporarily use such workarounds to adjust header names sent to them for
  the time it takes the application to be fixed. Please note that an
  application which requires such workarounds might be vulnerable to content
  smuggling attacks and must absolutely be fixed.

  Example:
    global
      h1-case-adjust content-length Content-Length

  See "h1-case-adjust-file", "option h1-case-adjust-bogus-client" and
  "option h1-case-adjust-bogus-server".

h1-case-adjust-file <hdrs-file>
  Defines a file containing a list of key/value pairs used to adjust the case
  of some header names before sending them to HTTP/1 clients or servers. The
  file <hdrs-file> must contain 2 header names per line. The first one must be
  in lower case and both must not differ except for their case. Lines which
  start with '#' are ignored, just like empty lines. Leading and trailing tabs
  and spaces are stripped. Duplicate entries are not allowed. Please note that
  no transformation will be applied unless "option h1-case-adjust-bogus-client"
  or "option h1-case-adjust-bogus-server" is specified in a proxy.

  If this directive is repeated, only the last one will be processed.  It is an
  alternative to the directive "h1-case-adjust" if a lot of header names need
  to be adjusted. Please read the risks associated with using this.

  See "h1-case-adjust", "option h1-case-adjust-bogus-client" and
  "option h1-case-adjust-bogus-server".

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>] [format <format>] [sample <ranges>:<smp_size>]
    <facility> [max level [min level]]
  Adds a global syslog server. Several global servers can be defined. They
  will receive logs for starts 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 datagram 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
          writable).

        - A file descriptor number in the form "fd@<number>", which may point
          to a pipe, terminal, or socket. In this case unbuffered logs are used
          and one writev() call per log is performed. This is a bit expensive
          but acceptable for most workloads. Messages sent this way will not be
          truncated but may be dropped, in which case the DroppedLogs counter
          will be incremented. The writev() call is atomic even on pipes for
          messages up to PIPE_BUF size, which POSIX recommends to be at least
          512 and which is 4096 bytes on most modern operating systems. Any
          larger message may be interleaved with messages from other processes.
          Exceptionally for debugging purposes the file descriptor may also be
          directed to a file, but doing so will significantly slow haproxy down
          as non-blocking calls will be ignored. Also there will be no way to
          purge nor rotate this file without restarting the process. Note that
          the configured syslog format is preserved, so the output is suitable
          for use with a TCP syslog server. See also the "short" and "raw"
          format below.

        - "stdout" / "stderr", which are respectively aliases for "fd@1" and
          "fd@2", see above.

        - A ring buffer in the form "ring@<name>", which will correspond to an
          in-memory ring buffer accessible over the CLI using the "show events"
          command, which will also list existing rings and their sizes. Such
          buffers are lost on reload or restart but when used as a complement
          this can help troubleshooting by having the logs instantly available.

        You may want to reference some environment variables in the address
        parameter, see section 2.3 about environment variables.

  <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-formatted logs may require larger values. You may also need to
           increase "tune.http.logurilen" if your request URIs are truncated.

  <format> is the log format used when generating syslog messages. It may be
           one of the following :

    rfc3164   The RFC3164 syslog message format. This is the default.
              (https://tools.ietf.org/html/rfc3164)

    rfc5424   The RFC5424 syslog message format.
              (https://tools.ietf.org/html/rfc5424)

    short     A message containing only a level between angle brackets such as
              '<3>', followed by the text. The PID, date, time, process name
              and system name are omitted. This is designed to be used with a
              local log server. This format is compatible with what the systemd
              logger consumes.

    raw       A message containing only the text. The level, PID, date, time,
              process name and system name are omitted. This is designed to be
              used in containers or during development, where the severity only
              depends on the file descriptor used (stdout/stderr).

  <ranges>   A list of comma-separated ranges to identify the logs to sample.
             This is used to balance the load of the logs to send to the log
             server. The limits of the ranges cannot be null. They are numbered
             from 1. The size or period (in number of logs) of the sample must be
             set with <sample_size> parameter.

  <sample_size>
             The size of the sample in number of logs to consider when balancing
             their logging loads. It is used to balance the load of the logs to
             send to the syslog server. This size must be greater or equal to the
             maximum of the high limits of the ranges.
             (see also <ranges> parameter).

  <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

             Note that the facility is ignored for the "short" and "raw"
             formats, but still required as a positional field. It is
             recommended to use "daemon" in this case to make it clear that
             it's only supposed to be used locally.

  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. See also the per-proxy "log-tag" directive.

lua-load <file>
  This global directive loads and executes a Lua file. This directive can be
  used multiple times.

master-worker [no-exit-on-failure]
  Master-worker mode. It is equivalent to the command line "-W" argument.
  This mode will launch a "master" which will monitor the "workers". Using
  this mode, you can reload HAProxy directly by sending a SIGUSR2 signal to
  the master. The master-worker mode is compatible either with the foreground
  or daemon mode. It is recommended to use this mode with multiprocess and
  systemd.
  By default, if a worker exits with a bad return code, in the case of a
  segfault for example, all workers will be killed, and the master will leave.
  It is convenient to combine this behavior with Restart=on-failure in a
  systemd unit file in order to relaunch the whole process. If you don't want
  this behavior, you must use the keyword "no-exit-on-failure".

  See also "-W" in the management guide.

mworker-max-reloads <number>
  In master-worker mode, this option limits the number of time a worker can
  survive to a reload. If the worker did not leave after a reload, once its
  number of reloads is greater than this number, the worker will receive a
  SIGTERM. This option helps to keep under control the number of workers.
  See also "show proc" in the Management Guide.

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. When set to a value
  larger than 1, threads are automatically disabled. USING MULTIPLE PROCESSES
  IS HARDER TO DEBUG AND IS REALLY DISCOURAGED. See also "daemon" and
  "nbthread".

nbthread <number>
  This setting is only available when support for threads was built in. It
  makes haproxy run on <number> threads. This is exclusive with "nbproc". While
  "nbproc" historically used to be the only way to use multiple processors, it
  also involved a number of shortcomings related to the lack of synchronization
  between processes (health-checks, peers, stick-tables, stats, ...) which do
  not affect threads. As such, any modern configuration is strongly encouraged
  to migrate away from "nbproc" to "nbthread". "nbthread" also works when
  HAProxy is started in foreground. On some platforms supporting CPU affinity,
  when nbproc is not used, the default "nbthread" value is automatically set to
  the number of CPUs the process is bound to upon startup. This means that the
  thread count can easily be adjusted from the calling process using commands
  like "taskset" or "cpuset". Otherwise, this value defaults to 1. The default
  value is reported in the output of "haproxy -vv". See also "nbproc".

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".

presetenv <name> <value>
  Sets environment variable <name> to value <value>. If the variable exists, it
  is NOT overwritten. The changes immediately take effect so that the next line
  in the configuration file sees the new value. See also "setenv", "resetenv",
  and "unsetenv".

resetenv [<name> ...]
  Removes all environment variables except the ones specified in argument. It
  allows to use a clean controlled environment before setting new values with
  setenv or unsetenv. Please note that some internal functions may make use of
  some environment variables, such as time manipulation functions, but also
  OpenSSL or even external checks. This must be used with extreme care and only
  after complete validation. The changes immediately take effect so that the
  next line in the configuration file sees the new environment. See also
  "setenv", "presetenv", and "unsetenv".

stats bind-process [ all | odd | even | <process_num>[-[process_num>]] ] ...
  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). Ranges can be partially defined. The higher bound can
  be omitted. In such case, it is replaced by the corresponding maximum
  value. A better option consists in using the "process" setting of the "stats
  socket" line to force the process on each line.

server-state-base <directory>
  Specifies the directory prefix to be prepended in front of all servers state
  file names which do not start with a '/'. See also "server-state-file",
  "load-server-state-from-file" and "server-state-file-name".

server-state-file <file>
  Specifies the path to the file containing state of servers. If the path starts
  with a slash ('/'), it is considered absolute, otherwise it is considered
  relative to the directory specified using "server-state-base" (if set) or to
  the current directory. Before reloading HAProxy, it is possible to save the
  servers' current state using the stats command "show servers state". The
  output of this command must be written in the file pointed by <file>. When
  starting up, before handling traffic, HAProxy will read, load and apply state
  for each server found in the file and available in its current running
  configuration. See also "server-state-base" and "show servers state",
  "load-server-state-from-file" and "server-state-file-name"

setenv <name> <value>
  Sets environment variable <name> to value <value>. If the variable exists, it
  is overwritten. The changes immediately take effect so that the next line in
  the configuration file sees the new value. See also "presetenv", "resetenv",
  and "unsetenv".

set-dumpable
  This option is better left disabled by default and enabled only upon a
  developer's request. If it has been enabled, it may still be forcibly
  disabled by prefixing it with the "no" keyword. It has no impact on
  performance nor stability but will try hard to re-enable core dumps that were
  possibly disabled by file size limitations (ulimit -f), core size limitations
  (ulimit -c), or "dumpability" of a process after changing its UID/GID (such
  as /proc/sys/fs/suid_dumpable on Linux). Core dumps might still be limited by
  the current directory's permissions (check what directory the file is started
  from), the chroot directory's permission (it may be needed to temporarily
  disable the chroot directive or to move it to a dedicated writable location),
  or any other system-specific constraint. For example, some Linux flavours are
  notorious for replacing the default core file with a path to an executable
  not even installed on the system (check /proc/sys/kernel/core_pattern). Often,
  simply writing "core", "core.%p" or "/var/log/core/core.%p" addresses the
  issue. When trying to enable this option waiting for a rare issue to
  re-appear, it's often a good idea to first try to obtain such a dump by
  issuing, for example, "kill -11" to the haproxy process and verify that it
  leaves a core where expected when dying.

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 up to TLSv1.2 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. For background
  information and recommendations see e.g.
  (https://wiki.mozilla.org/Security/Server_Side_TLS) and
  (https://mozilla.github.io/server-side-tls/ssl-config-generator/). For TLSv1.3
  cipher configuration, please check the "ssl-default-bind-ciphersuites" keyword.
  Please check the "bind" keyword for more information.

ssl-default-bind-ciphersuites <ciphersuites>
  This setting is only available when support for OpenSSL was built in and
  OpenSSL 1.1.1 or later was used to build HAProxy. It sets the default string
  describing the list of cipher algorithms ("cipher suite") that are negotiated
  during the TLSv1.3 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 under the section "ciphersuites". For
  cipher configuration for TLSv1.2 and earlier, please check the
  "ssl-default-bind-ciphers" keyword. 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 ssl-min-ver TLSv1.0 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 up to TLSv1.2 with the server,
  for all "server" lines which do not explicitly define theirs. The format of
  the string is defined in "man 1 ciphers" from OpenSSL man pages. For background
  information and recommendations see e.g.
  (https://wiki.mozilla.org/Security/Server_Side_TLS) and
  (https://mozilla.github.io/server-side-tls/ssl-config-generator/).
  For TLSv1.3 cipher configuration, please check the
  "ssl-default-server-ciphersuites" keyword. Please check the "server" keyword
  for more information.

ssl-default-server-ciphersuites <ciphersuites>
  This setting is only available when support for OpenSSL was built in and
  OpenSSL 1.1.1 or later was used to build HAProxy. It sets the default
  string describing the list of cipher algorithms that are negotiated during
  the TLSv1.3 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" from OpenSSL man pages under the section "ciphersuites". For
  cipher configuration for TLSv1.2 and earlier, please check the
  "ssl-default-server-ciphers" keyword. 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-dh-param-file <file>
  This setting is only available when support for OpenSSL was built in. It sets
  the default DH parameters that are used during the SSL/TLS handshake when
  ephemeral Diffie-Hellman (DHE) key exchange is used, for all "bind" lines
  which do not explicitly define theirs. It will be overridden by custom DH
  parameters found in a bind certificate file if any. If custom DH parameters
  are not specified either by using ssl-dh-param-file or by setting them
  directly in the certificate file, pre-generated DH parameters of the size
  specified by tune.ssl.default-dh-param will be used. Custom parameters are
  known to be more secure and therefore their use is recommended.
  Custom DH parameters may be generated by using the OpenSSL command
  "openssl dhparam <size>", where size should be at least 2048, as 1024-bit DH
  parameters should not be considered secure anymore.

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 9.3 "Unix Socket commands" of Management Guide 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.

unsetenv [<name> ...]
  Removes environment variables specified in arguments. This can be useful to
  hide some sensitive information that are occasionally inherited from the
  user's environment during some operations. Variables which did not exist are
  silently ignored so that after the operation, it is certain that none of
  these variables remain. The changes immediately take effect so that the next
  line in the configuration file will not see these variables. See also
  "setenv", "presetenv", and "resetenv".

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.

51degrees-data-file <file path>
  The path of the 51Degrees data file to provide device detection services. The
  file should be unzipped and accessible by HAProxy with relevant permissions.

  Please note that this option is only available when haproxy has been
  compiled with USE_51DEGREES.

51degrees-property-name-list [<string> ...]
  A list of 51Degrees property names to be load from the dataset. A full list
  of names is available on the 51Degrees website:
  https://51degrees.com/resources/property-dictionary

  Please note that this option is only available when haproxy has been
  compiled with USE_51DEGREES.

51degrees-property-separator <char>
  A char that will be appended to every property value in a response header
  containing 51Degrees results. If not set that will be set as ','.

  Please note that this option is only available when haproxy has been
  compiled with USE_51DEGREES.

51degrees-cache-size <number>
  Sets the size of the 51Degrees converter cache to <number> entries. This
  is an LRU cache which reminds previous device detections and their results.
  By default, this cache is disabled.

  Please note that this option is only available when haproxy has been
  compiled with USE_51DEGREES.

wurfl-data-file <file path>
  The path of the WURFL data file to provide device detection services. The
  file should be accessible by HAProxy with relevant permissions.

  Please note that this option is only available when haproxy has been compiled
  with USE_WURFL=1.

wurfl-information-list [<capability>]*
  A space-delimited list of WURFL capabilities, virtual capabilities, property
  names we plan to use in injected headers. A full list of capability and
  virtual capability names is available on the Scientiamobile website :

      https://www.scientiamobile.com/wurflCapability

  Valid WURFL properties are:
  - wurfl_id                    Contains the device ID of the matched device.

  - wurfl_root_id               Contains the device root ID of the matched
                                device.

  - wurfl_isdevroot             Tells if the matched device is a root device.
                                Possible values are "TRUE" or "FALSE".

  - wurfl_useragent             The original useragent coming with this
                                particular web request.

  - wurfl_api_version           Contains a string representing the currently
                                used Libwurfl API version.

  - wurfl_info                  A string containing information on the parsed
                                wurfl.xml and its full path.

  - wurfl_last_load_time        Contains the UNIX timestamp of the last time
                                WURFL has been loaded successfully.

  - wurfl_normalized_useragent  The normalized useragent.

  Please note that this option is only available when haproxy has been compiled
  with USE_WURFL=1.

wurfl-information-list-separator <char>
  A char that will be used to separate values in a response header containing
  WURFL results. If not set that a comma (',') will be used by default.

  Please note that this option is only available when haproxy has been compiled
  with USE_WURFL=1.

wurfl-patch-file [<file path>]
  A list of WURFL patch file paths. Note that patches are loaded during startup
  thus before the chroot.

  Please note that this option is only available when haproxy has been compiled
  with USE_WURFL=1.

wurfl-cache-size <size>
  Sets the WURFL Useragent cache size. For faster lookups, already processed user
  agents are kept in a LRU cache :
  - "0"     : no cache is used.
  - <size>  : size of lru cache in elements.

  Please note that this option is only available when haproxy has been compiled
  with USE_WURFL=1.

strict-limits
  Makes process fail at startup when a setrlimit fails. Haproxy is tries to set
  the best setrlimit according to what has been calculated. If it fails, it
  will emit a warning. Use this option if you want an explicit failure of
  haproxy when those limits fail. This option is disabled by default. If it has
  been enabled, it may still be forcibly disabled by prefixing it with the "no"
  keyword.

3.2. Performance tuning
-----------------------

busy-polling
  In some situations, especially when dealing with low latency on processors
  supporting a variable frequency or when running inside virtual machines, each
  time the process waits for an I/O using the poller, the processor goes back
  to sleep or is offered to another VM for a long time, and it causes
  excessively high latencies. This option provides a solution preventing the
  processor from sleeping by always using a null timeout on the pollers. This
  results in a significant latency reduction (30 to 100 microseconds observed)
  at the expense of a risk to overheat the processor. It may even be used with
  threads, in which case improperly bound threads may heavily conflict,
  resulting in a worse performance and high values for the CPU stolen fields
  in "show info" output, indicating which threads are misconfigured. It is
  important not to let the process run on the same processor as the network
  interrupts when this option is used. It is also better to avoid using it on
  multiple CPU threads sharing the same core. This option is disabled by
  default. If it has been enabled, it may still be forcibly disabled by
  prefixing it with the "no" keyword. It is ignored by the "select" and
  "poll" pollers.

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). If this value is not set, it will automatically be
  calculated based on the current file descriptors limit reported by the
  "ulimit -n" command, possibly reduced to a lower value if a memory limit
  is enforced, based on the buffer size, memory allocated to compression, SSL
  cache size, and use or not of SSL and the associated maxsslconn (which can
  also be automatic).

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.
  If this value is not set, but a memory limit is enforced, this value will be
  automatically computed based on the memory limit, maxconn,  the buffer size,
  memory allocated to compression, SSL cache size, and use of SSL in either
  frontends, backends or both. If neither maxconn nor maxsslconn are specified
  when there is a memory limit, haproxy will automatically adjust these values
  so that 100% of the connections can be made over SSL with no risk, and will
  consider the sides where it is enabled (frontend, backend, both).

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".

noevports
  Disables the use of the event ports event polling system on SunOS systems
  derived from Solaris 10 and later. It is equivalent to the command-line
  argument "-dv". 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", "noepoll" and
  "noevports".

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.

noreuseport
  Disables the use of SO_REUSEPORT - see socket(7). It is equivalent to the
  command line argument "-dR".

profiling.tasks { auto | on | off }
  Enables ('on') or disables ('off') per-task CPU profiling. When set to 'auto'
  the profiling automatically turns on a thread when it starts to suffer from
  an average latency of 1000 microseconds or higher as reported in the
  "avg_loop_us" activity field, and automatically turns off when the latency
  returns below 990 microseconds (this value is an average over the last 1024
  loops so it does not vary quickly and tends to significantly smooth short
  spikes). It may also spontaneously trigger from time to time on overloaded
  systems, containers, or virtual machines, or when the system swaps (which
  must absolutely never happen on a load balancer).

  CPU profiling per task can be very convenient to report where the time is
  spent and which requests have what effect on which other request. Enabling
  it will typically affect the overall's performance by less than 1%, thus it
  is recommended to leave it to the default 'auto' value so that it only
  operates when a problem is identified. This feature requires a system
  supporting the clock_gettime(2) syscall with clock identifiers
  CLOCK_MONOTONIC and CLOCK_THREAD_CPUTIME_ID, otherwise the reported time will
  be zero. This option may be changed at run time using "set profiling" on the
  CLI.

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.

ssl-engine <name> [algo <comma-separated list of algorithms>]
  Sets the OpenSSL engine to <name>. List of valid values for <name> may be
  obtained using the command "openssl engine". This statement may be used
  multiple times, it will simply enable multiple crypto engines. Referencing an
  unsupported engine will prevent haproxy from starting. Note that many engines
  will lead to lower HTTPS performance than pure software with recent
  processors. The optional command "algo" sets the default algorithms an ENGINE
  will supply using the OPENSSL function ENGINE_set_default_string(). A value
  of "ALL" uses the engine for all cryptographic operations. If no list of
  algo is specified then the value of "ALL" is used. A comma-separated list
  of different algorithms may be specified, including: RSA, DSA, DH, EC, RAND,
  CIPHERS, DIGESTS, PKEY, PKEY_CRYPTO, PKEY_ASN1. This is the same format that
  openssl configuration file uses:
  https://www.openssl.org/docs/man1.0.2/apps/config.html

ssl-mode-async
  Adds SSL_MODE_ASYNC mode to the SSL context. This enables asynchronous TLS
  I/O operations if asynchronous capable SSL engines are used. The current
  implementation supports a maximum of 32 engines. The Openssl ASYNC API
  doesn't support moving read/write buffers and is not compliant with
  haproxy's buffer management. So the asynchronous mode is disabled on
  read/write  operations (it is only enabled during initial and renegotiation
  handshakes).

tune.buffers.limit <number>
  Sets a hard limit on the number of buffers which may be allocated per process.
  The default value is zero which means unlimited. The minimum non-zero value
  will always be greater than "tune.buffers.reserve" and should ideally always
  be about twice as large. Forcing this value can be particularly useful to
  limit the amount of memory a process may take, while retaining a sane
  behavior. When this limit is reached, sessions which need a buffer wait for
  another one to be released by another session. Since buffers are dynamically
  allocated and released, the waiting time is very short and not perceptible
  provided that limits remain reasonable. In fact sometimes reducing the limit
  may even increase performance by increasing the CPU cache's efficiency. Tests
  have shown good results on average HTTP traffic with a limit to 1/10 of the
  expected global maxconn setting, which also significantly reduces memory
  usage. The memory savings come from the fact that a number of connections
  will not allocate 2*tune.bufsize. It is best not to touch this value unless
  advised to do so by an haproxy core developer.

tune.buffers.reserve <number>
  Sets the number of buffers which are pre-allocated and reserved for use only
  during memory shortage conditions resulting in failed memory allocations. The
  minimum value is 2 and is also the default. There is no reason a user would
  want to change this value, it's mostly aimed at haproxy core developers.

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. In
  addition, use of HTTP/2 mandates that this value must be 16384 or more. If an
  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). Note that the
  value set using this parameter will automatically be rounded up to the next
  multiple of 8 on 32-bit machines and 16 on 64-bit machines.

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.fail-alloc
  If compiled with DEBUG_FAIL_ALLOC, gives the percentage of chances an
  allocation attempt fails. Must be between 0 (no failure) and 100 (no
  success). This is useful to debug and make sure memory failures are handled
  gracefully.

tune.h2.header-table-size <number>
  Sets the HTTP/2 dynamic header table size. It defaults to 4096 bytes and
  cannot be larger than 65536 bytes. A larger value may help certain clients
  send more compact requests, depending on their capabilities. This amount of
  memory is consumed for each HTTP/2 connection. It is recommended not to
  change it.

tune.h2.initial-window-size <number>
  Sets the HTTP/2 initial window size, which is the number of bytes the client
  can upload before waiting for an acknowledgment from haproxy. This setting
  only affects payload contents (i.e. the body of POST requests), not headers.
  The default value is 65535, which roughly allows up to 5 Mbps of upload
  bandwidth per client over a network showing a 100 ms ping time, or 500 Mbps
  over a 1-ms local network. It can make sense to increase this value to allow
  faster uploads, or to reduce it to increase fairness when dealing with many
  clients. It doesn't affect resource usage.

tune.h2.max-concurrent-streams <number>
  Sets the HTTP/2 maximum number of concurrent streams per connection (ie the
  number of outstanding requests on a single connection). The default value is
  100. A larger one may slightly improve page load time for complex sites when
  visited over high latency networks, but increases the amount of resources a
  single client may allocate. A value of zero disables the limit so a single
  client may create as many streams as allocatable by haproxy. It is highly
  recommended not to change this value.

tune.h2.max-frame-size <number>
  Sets the HTTP/2 maximum frame size that haproxy announces it is willing to
  receive to its peers. The default value is the largest between 16384 and the
  buffer size (tune.bufsize). In any case, haproxy will not announce support
  for frame sizes larger than buffers. The main purpose of this setting is to
  allow to limit the maximum frame size setting when using large buffers. Too
  large frame sizes might have performance impact or cause some peers to
  misbehave. It is highly recommended not to change this value.

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.logurilen <number>
  Sets the maximum length of request URI in logs. This prevents truncating long
  request URIs with valuable query strings in log lines. This is not related
  to syslog limits. If you increase this limit, you may also increase the
  'log ... len yyy' parameter. Your syslog daemon may also need specific
  configuration directives too.
  The default value is 1024.

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. The accepted range is
  1..32767. 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 (e.g. read a page before
  clicking). There should be no reason for changing this value. Please check
  tune.ssl.maxrecord below.

tune.listener.multi-queue { on | off }
  Enables ('on') or disables ('off') the listener's multi-queue accept which
  spreads the incoming traffic to all threads a "bind" line is allowed to run
  on instead of taking them for itself. This provides a smoother traffic
  distribution and scales much better, especially in environments where threads
  may be unevenly loaded due to external activity (network interrupts colliding
  with one thread for example). This option is enabled by default, but it may
  be forcefully disabled for troubleshooting or for situations where it is
  estimated that the operating system already provides a good enough
  distribution and connections are extremely short-lived.

tune.lua.forced-yield <number>
  This directive forces the Lua engine to execute a yield each <number> of
  instructions executed. This permits interrupting a long script and allows the
  HAProxy scheduler to process other tasks like accepting connections or
  forwarding traffic. The default value is 10000 instructions. If HAProxy often
  executes some Lua code but more responsiveness is required, this value can be
  lowered. If the Lua code is quite long and its result is absolutely required
  to process the data, the <number> can be increased.

tune.lua.maxmem
  Sets the maximum amount of RAM in megabytes per process usable by Lua. By
  default it is zero which means unlimited. It is important to set a limit to
  ensure that a bug in a script will not result in the system running out of
  memory.

tune.lua.session-timeout <timeout>
  This is the execution timeout for the Lua sessions. This is useful for
  preventing infinite loops or spending too much time in Lua. This timeout
  counts only the pure Lua runtime. If the Lua does a sleep, the sleep is
  not taken in account. The default timeout is 4s.

tune.lua.task-timeout <timeout>
  Purpose is the same as "tune.lua.session-timeout", but this timeout is
  dedicated to the tasks. By default, this timeout isn't set because a task may
  remain alive during of the lifetime of HAProxy. For example, a task used to
  check servers.

tune.lua.service-timeout <timeout>
  This is the execution timeout for the Lua services. This is useful for
  preventing infinite loops or spending too much time in Lua. This timeout
  counts only the pure Lua runtime. If the Lua does a sleep, the sleep is
  not taken in account. The default timeout is 4s.

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.pattern.cache-size <number>
  Sets the size of the pattern lookup cache to <number> entries. This is an LRU
  cache which reminds previous lookups and their results. It is used by ACLs
  and maps on slow pattern lookups, namely the ones using the "sub", "reg",
  "dir", "dom", "end", "bin" match methods as well as the case-insensitive
  strings. It applies to pattern expressions which means that it will be able
  to memorize the result of a lookup among all the patterns specified on a
  configuration line (including all those loaded from files). It automatically
  invalidates entries which are updated using HTTP actions or on the CLI. The
  default cache size is set to 10000 entries, which limits its footprint to
  about 5 MB per process/thread on 32-bit systems and 8 MB per process/thread
  on 64-bit systems, as caches are thread/process local. There is a very low
  risk of collision in this cache, which is in the order of the size of the
  cache divided by 2^64. Typically, at 10000 requests per second with the
  default cache size of 10000 entries, there's 1% chance that a brute force
  attack could cause a single collision after 60 years, or 0.1% after 6 years.
  This is considered much lower than the risk of a memory corruption caused by
  aging components. If this is not acceptable, the cache can be disabled by
  setting this parameter to 0.

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.pool-low-fd-ratio <number>
  This setting sets the max number of file descriptors (in percentage) used by
  haproxy globally against the maximum number of file descriptors haproxy can
  use before we stop putting connection into the idle pool for reuse. The
  default is 20.

tune.pool-high-fd-ratio <number>
  This setting sets the max number of file descriptors (in percentage) used by
  haproxy globally against the maximum number of file descriptors haproxy can
  use before we start killing idle connections when we can't reuse a connection
  and we have to create a new one. The default is 25 (one quarter of the file
  descriptor will mean that roughly half of the maximum front connections can
  keep an idle connection behind, anything beyond this probably doesn't make
  much sense in the general case when targeting connection reuse).

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 auto-tune this value depending on the amount of available memory.
  However it can sometimes help to set it to very low values (e.g. 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.recv_enough <number>
  HAProxy uses some hints to detect that a short read indicates the end of the
  socket buffers. One of them is that a read returns more than <recv_enough>
  bytes, which defaults to 10136 (7 segments of 1448 each). This default value
  may be changed by this setting to better deal with workloads involving lots
  of short messages such as telnet or SSH sessions.

tune.runqueue-depth <number>
  Sets the maximum amount of task that can be processed at once when running
  tasks. The default value is 200. Increasing it may incur latency when
  dealing with I/Os, making it too small can incur extra overhead.

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 auto-tune this value depending on the amount of available memory.
  However it can sometimes help to set it to very low values (e.g. 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 option 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 either directly
  in the certificate file or by using the ssl-dh-param-file parameter.

tune.ssl.ssl-ctx-cache-size <number>
  Sets the size of the cache used to store generated certificates to <number>
  entries. This is a LRU cache. Because generating a SSL certificate
  dynamically is expensive, they are cached. The default cache size is set to
  1000 entries.

tune.ssl.capture-cipherlist-size <number>
  Sets the maximum size of the buffer used for capturing client-hello cipher
  list. If the value is 0 (default value) the capture is disabled, otherwise
  a buffer is allocated for each SSL/TLS connection.

tune.vars.global-max-size <size>
tune.vars.proc-max-size <size>
tune.vars.reqres-max-size <size>
tune.vars.sess-max-size <size>
tune.vars.txn-max-size <size>
  These five tunes help to manage the maximum amount of memory used by the
  variables system. "global" limits the overall amount of memory available for
  all scopes. "proc" limits the memory for the process scope, "sess" limits the
  memory for the session scope, "txn" for the transaction scope, and "reqres"
  limits the memory for each request or response processing.
  Memory accounting is hierarchical, meaning more coarse grained limits include
  the finer grained ones: "proc" includes "sess", "sess" includes "txn", and
  "txn" includes "reqres".

  For example, when "tune.vars.sess-max-size" is limited to 100,
  "tune.vars.txn-max-size" and "tune.vars.reqres-max-size" cannot exceed
  100 either. If we create a variable "txn.var" that contains 100 bytes,
  all available space is consumed.
  Notice that exceeding the limits at runtime will not result in an error
  message, but values might be cut off or corrupted. So make sure to accurately
  plan for the amount of space needed to store all your variables.

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 on the system's
  capabilities, different algorithms are supported. For example, modern Glibc
  based Linux systems support MD5, SHA-256, SHA-512, and, of course, the
  classic DES-based method of encrypting passwords.

  Attention: Be aware that using encrypted passwords might cause significantly
  increased CPU usage, depending on the number of requests, and the algorithm
  used. For any of the hashed variants, the password for each request must
  be processed through the chosen algorithm, before it can be compared to the
  value specified in the config file. Most current algorithms are deliberately
  designed to be expensive to compute to achieve resistance against brute
  force attacks. They do not simply salt/hash the clear text password once,
  but thousands of times. This can quickly become a major factor in haproxy's
  overall CPU consumption!

  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 propagate entries of any data-types 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. The pushed
values overwrite remote ones without aggregation. 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.
Note that 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.

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

bind [<address>]:<port_range> [, ...] [param*]
  Defines the binding parameters of the local peer of this "peers" section.
  Such lines are not supported with "peer" line in the same "peers" section.

disabled
  Disables a peers section. It disables both listening and any synchronization
  related to this section. This is provided to disable synchronization of stick
  tables without having to comment out all "peers" references.

default-bind [param*]
  Defines the binding parameters for the local peer, excepted its address.

default-server [param*]
  Change default options for a server in a "peers" section.

  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.


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

enable
  This re-enables a disabled peers section which was previously disabled.

log <address> [len <length>] [format <format>] [sample <ranges>:<smp_size>]
    <facility> [<level> [<minlevel>]]
  "peers" sections support the same "log" keyword as for the proxies to
  log information about the "peers" listener. See "log" option for proxies for
  more details.

peer <peername> <ip>:<port> [param*]
  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.

  You may want to reference some environment variables in the address
  parameter, see section 2.3 about environment variables.

  Note: "peer" keyword may transparently be replaced by "server" keyword (see
  "server" keyword explanation below).

server <peername> [<ip>:<port>] [param*]
  As previously mentioned, "peer" keyword may be replaced by "server" keyword
  with a support for all "server" parameters found in 5.2 paragraph.
  If the underlying peer is local, <ip>:<port> parameters must not be present.
  These parameters must  be provided on a "bind" line (see "bind" keyword
  of this "peers" section).
  Some of these parameters are irrelevant for "peers" sections.


  Example:
    # The old way.
    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

   Example:
     peers mypeers
         bind 127.0.0.11:10001 ssl crt mycerts/pem
         default-server ssl verify none
         server hostA  127.0.0.10:10000
         server hostB  #local peer


table <tablename> type {ip | integer | string [len <length>] | binary [len <length>]}
      size <size> [expire <expire>] [nopurge] [store <data_type>]*

  Configure a stickiness table for the current section. This line is parsed
  exactly the same way as the "stick-table" keyword in others section, except
  for the "peers" argument which is not required here and with an additional
  mandatory first parameter to designate the stick-table. Contrary to others
  sections, there may be several "table" lines in "peers" sections (see also
  "stick-table" keyword).

  Also be aware of the fact that "peers" sections have their own stick-table
  namespaces to avoid collisions between stick-table names identical in
  different "peers" section. This is internally handled prepending the "peers"
  sections names to the name of the stick-tables followed by a '/' character.
  If somewhere else in the configuration file you have to refer to such
  stick-tables declared in "peers" sections you must use the prefixed version
  of the stick-table name as follows:

      peers mypeers
          peer A ...
          peer B ...
          table t1 ...

      frontend fe1
          tcp-request content track-sc0 src table mypeers/t1

  This is also this prefixed version of the stick-table names which must be
  used to refer to stick-tables through the CLI.

  About "peers" protocol, as only "peers" belonging to the same section may
  communicate with each others, there is no need to do such a distinction.
  Several "peers" sections may declare stick-tables with the same name.
  This is shorter version of the stick-table name  which is sent over the network.
  There is only a '/' character as prefix to avoid stick-table name collisions between
  stick-tables declared as backends and stick-table declared in "peers" sections
  as follows in this weird but supported configuration:

      peers mypeers
          peer A ...
          peer B ...
          table t1 type string size 10m store gpc0

      backend t1
          stick-table type string size 10m store gpc0 peers mypeers

  Here "t1" table declared in "mypeeers" section has "mypeers/t1" as global name.
  "t1" table declared as a backend as "t1" as global name. But at peer protocol
  level the former table is named "/t1", the latter is again named "t1".

3.6. Mailers
------------
It is possible to send email alerts when the state of servers changes.
If configured email alerts are sent to each mailer that is configured
in a mailers section. Email is sent to mailers using SMTP.

mailers <mailersect>
  Creates a new mailer list with the name <mailersect>. It is an
  independent section which is referenced by one or more proxies.

mailer <mailername> <ip>:<port>
  Defines a mailer inside a mailers section.

  Example:
    mailers mymailers
        mailer smtp1 192.168.0.1:587
        mailer smtp2 192.168.0.2:587

    backend mybackend
        mode tcp
        balance roundrobin

        email-alert mailers mymailers
        email-alert from test1@horms.org
        email-alert to test2@horms.org

        server srv1 192.168.0.30:80
        server srv2 192.168.0.31:80

timeout mail <time>
  Defines the time available for a mail/connection to be made and send to
  the mail-server. If not defined the default value is 10 seconds. To allow
  for at least two SYN-ACK packets to be send during initial TCP handshake it
  is advised to keep this value above 4 seconds.

  Example:
    mailers mymailers
        timeout mail 20s
        mailer smtp1 192.168.0.1:587

3.7. Programs
-------------
In master-worker mode, it is possible to launch external binaries with the
master, these processes are called programs. These programs are launched and
managed the same way as the workers.

During a reload of HAProxy, those processes are dealing with the same
sequence as a worker:

  - the master is re-executed
  - the master sends a SIGUSR1 signal to the program
  - if "option start-on-reload" is not disabled, the master launches a new
    instance of the program

During a stop, or restart, a SIGTERM is sent to the programs.

program <name>
  This is a new program section, this section will create an instance <name>
  which is visible in "show proc" on the master CLI. (See "9.4. Master CLI" in
  the management guide).

command <command> [arguments*]
  Define the command to start with optional arguments. The command is looked
  up in the current PATH if it does not include an absolute path. This is a
  mandatory option of the program section. Arguments containing spaces must
  be enclosed in quotes or double quotes or be prefixed by a backslash.

user <user name>
  Changes the executed command user ID to the <user name> from /etc/passwd.
  See also "group".

group <group name>
  Changes the executed command group ID to the <group name> from /etc/group.
  See also "user".

option start-on-reload
no option start-on-reload
  Start (or not) a new instance of the program upon a reload of the master.
  The default is to start a new instance. This option may only be used in a
  program section.


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 4 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.

  - 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.

  - CLO: close ("option httpclose"): the connection is closed after the end of
    the response and "Connection: close" appended in both directions.

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 close is the strongest.

                   Backend mode

                | KAL | SCL | CLO
            ----+-----+-----+----
            KAL | KAL | SCL | CLO
            ----+-----+-----+----
   mode     SCL | SCL | SCL | CLO
            ----+-----+-----+----
            CLO | CLO | CLO | CLO



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, e.g. "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
backlog                                   X          X         X         -
balance                                   X          -         X         X
bind                                      -          X         X         -
bind-process                              X          X         X         X
capture cookie                            -          X         X         -
capture request header                    -          X         X         -
capture response header                   -          X         X         -
compression                               X          X         X         X
cookie                                    X          -         X         X
declare capture                           -          X         X         -
default-server                            X          -         X         X
default_backend                           X          X         X         -
description                               -          X         X         X
disabled                                  X          X         X         X
dispatch                                  -          -         X         X
email-alert from                          X          X         X         X
email-alert level                         X          X         X         X
email-alert mailers                       X          X         X         X
email-alert myhostname                    X          X         X         X
email-alert to                            X          X         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