<?xml version="1.0"?>

<!DOCTYPE module SYSTEM "../../../../dtd/module.dtd">

<module name="Module ngx_http_proxy_module"
        link="/en/docs/http/ngx_http_proxy_module.html"
        lang="en">

<section id="summary">

<para>
The <literal>ngx_http_proxy_module</literal> module allows to pass
requests to another server.
</para>

</section>


<section id="example" name="Example Configuration">

<para>
<example>
location / {
    proxy_pass       http://localhost:8000;
    proxy_set_header Host      $host;
    proxy_set_header X-Real-IP $remote_addr;
}
</example>
</para>

</section>


<section id="directives" name="Directives">

<directive name="proxy_buffer_size">
<syntax><value>size</value></syntax>
<default>4k|8k</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets <value>size</value> of the buffer used for reading the first part
of a response received from the proxied server.
This part usually contains a small response header.
By default, the buffer size is equal to the size of one
buffer set by the <link id="proxy_buffers"/> directive.
It can be made smaller however.
</para>

</directive>


<directive name="proxy_buffering">
<syntax><literal>on</literal> | <literal>off</literal></syntax>
<default>on</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Enables or disables buffering a response from the proxied server.
</para>

<para>
When buffering is enabled, nginx receives a response from the proxied server
as soon as possible, saving it into buffers set by the
<link id="proxy_buffer_size"/> and <link id="proxy_buffers"/> directives.
If the whole response does not fit into memory, part of it is saved to a disk.
</para>

<para>
When buffering is disabled, a response is passed to a client synchronously,
immediately upon receipt.
nginx will not try to read the whole response from the proxied server.
The maximum size of the data that nginx can receive from the server
at a time is set by the <link id="proxy_buffer_size"/> directive.
</para>

</directive>


<directive name="proxy_buffers">
<syntax><value>number</value> <value>size</value></syntax>
<default>8 4k|8k</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets the <value>number</value> and <value>size</value> of
buffers used for reading a response from the proxied server,
for a single connection.
By default, the buffer size is equal to one memory page.
This is either 4K or 8K, depending on a platform.
</para>

</directive>


<directive name="proxy_cache">
<syntax><value>zone</value> | <literal>off</literal></syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Defines a zone used for caching.
The same zone can be used in several places.
The <literal>off</literal> parameter disables caching inherited
from the previous configuration level.
</para>

</directive>


<directive name="proxy_cache_bypass">
<syntax><value>string</value> ...</syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Defines conditions under which the response will not be taken from a cache.
If at least one value of the string parameters is not empty and is not
equal to “0” then the response will not be taken from the cache:
<example>
proxy_cache_bypass $cookie_nocache $arg_nocache$arg_comment;
proxy_cache_bypass $http_pragma    $http_authorization;
</example>
Can be used along with the <link id="proxy_no_cache"/> directive.
</para>

</directive>


<directive name="proxy_cache_key">
<syntax><value>string</value></syntax>
<default>$scheme$proxy_host$request_uri</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Defines a key for caching, for example
<example>
proxy_cache_key "$host$request_uri $cookie_user";
</example>
By default, the directive’s value is close to the string
<example>
proxy_cache_key $scheme$proxy_host$uri$is_args$args;
</example>
</para>

</directive>


<directive name="proxy_cache_lock">
<syntax><literal>on</literal> | <literal>off</literal></syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.1.12</appeared-in>

<para>
When enabled, only one request at a time will be allowed to populate
a new cache element identified according to the <link id="proxy_cache_key"/>
directive by passing a request to a proxied server.
Other requests of the same cache element will either wait
for a response to appear in the cache, or the cache lock for
this element to be released, up to the time set by the
<link id="proxy_cache_lock_timeout"/> directive.
</para>

</directive>


<directive name="proxy_cache_lock_timeout">
<syntax><value>time</value></syntax>
<default>5s</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.1.12</appeared-in>

<para>
Sets a timeout for <link id="proxy_cache_lock"/>.
</para>

</directive>


<directive name="proxy_cache_min_uses">
<syntax><value>number</value></syntax>
<default>1</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets the <value>number</value> of requests after which the response
will be cached.
</para>

</directive>


<directive name="proxy_cache_path">
<syntax>
  <value>path</value>
  [<literal>levels</literal>=<value>levels</value>]
  <literal>keys_zone</literal>=<value>name</value>:<value>size</value>
  [<literal>inactive</literal>=<value>time</value>]
  [<literal>max_size</literal>=<value>size</value>]</syntax>
<default/>
<context>http</context>

<para>
Sets path and other parameters of a cache.
Cache data are stored in files.
Both the key and file name in a cache are a result of
applying the MD5 function to the proxied URL.

The <literal>levels</literal> parameter defines hierarchy levels of a cache.
For example, in the following configuration
<example>
proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=one:10m;
</example>
file names in a cache will look like this:
<example>
/data/nginx/cache/<emphasis>c</emphasis>/<emphasis>29</emphasis>/b7f54b2df7773722d382f4809d650<emphasis>29c</emphasis>
</example>
</para>

<para>
A cached response is first written to a temporary file, then a file is renamed.
Starting from version 0.8.9 temporary files and the cache can be put on
different file systems but be aware that in this case a file is copied
across two file systems instead of the cheap rename operation.
It is thus recommended that for any given location both cache and a directory
holding temporary files set by the <link id="proxy_temp_path"/> directive
are put on the same file system.
</para>

<para>
In addition, all active keys and information about data are stored
in a shared memory zone, whose <value>name</value> and <value>size</value>
are configured by the <literal>keys_zone</literal> parameter.
Cached data that are not accessed during the time specified by the
<literal>inactive</literal> parameter get removed from the cache
regardless of their freshness.
By default, <literal>inactive</literal> is set to 10 minutes.
</para>

<para>
The special process “cache manager” monitors the maximum cache size set
by the <literal>max_size</literal> parameter;
when this size is exceeded it removes the least recently used data.
</para>

</directive>


<directive name="proxy_cache_use_stale">
<syntax>
  <literal>error</literal> |
  <literal>timeout</literal> |
  <literal>invalid_header</literal> |
  <literal>updating</literal> |
  <literal>http_500</literal> |
  <literal>http_502</literal> |
  <literal>http_503</literal> |
  <literal>http_504</literal> |
  <literal>http_404</literal> |
  <literal>off</literal>
  ...</syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
If an error occurs while working with the proxied server it is possible
to use a stale cached response.
This directives determines in which cases it is permitted.
The directive’s parameters match those of the
<link id="proxy_next_upstream"/> directive.
Additionally, the <literal>updating</literal> parameter permits
to use a stale cached response if it is currently being updated.
</para>

</directive>


<directive name="proxy_cache_valid">
<syntax>[<value>code</value> ...] <value>time</value></syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets caching time for different response codes.
For example, the following directives
<example>
proxy_cache_valid 200 302 10m;
proxy_cache_valid 404      1m;
</example>
set 10 minutes of caching for responses with codes 200 and 302,
and 1 minute for responses with code 404.
</para>

<para>
If only caching <value>time</value> is specified
<example>
proxy_cache_valid 5m;
</example>
then only 200, 301, and 302 responses are cached.
</para>

<para>
In addition, it can be specified to cache any responses using the
<literal>any</literal> parameter:
<example>
proxy_cache_valid 200 302 10m;
proxy_cache_valid 301      1h;
proxy_cache_valid any      1m;
</example>
</para>

</directive>


<directive name="proxy_connect_timeout">
<syntax><value>time</value></syntax>
<default>60s</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Defines a timeout for establishing a connection with the proxied server.
It should be noted that this timeout cannot usually exceed 75 seconds.
</para>

</directive>


<directive name="proxy_hide_header">
<syntax><value>field</value></syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
By default,
nginx does not pass the header fields <header>Date</header>,
<header>Server</header>, <header>X-Pad</header>, and
<header>X-Accel-...</header> from the response of a proxied
server to a client.
The <literal>proxy_hide_header</literal> directive sets additional fields
that will not be passed.
If, on the contrary, the passing of fields needs to be permitted,
the <link id="proxy_pass_header"/> directive can be used.
</para>

</directive>


<directive name="proxy_http_version">
<syntax><literal>1.0</literal> | <literal>1.1</literal></syntax>
<default>1.0</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.1.4</appeared-in>

<para>
Sets the HTTP protocol version for proxying.
By default, version 1.0 is used.
Version 1.1 is recommended for use with
<link doc="ngx_http_upstream_module.xml" id="keepalive"/>
connections.
</para>

</directive>


<directive name="proxy_ignore_client_abort">
<syntax><literal>on</literal> | <literal>off</literal></syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Determines should the connection with a proxied server be
closed if a client closes a connection without waiting
for a response.
</para>

</directive>


<directive name="proxy_ignore_headers">
<syntax><value>field</value> ...</syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Disables processing of certain response header fields from the proxied server.
The following fields can be ignored: <header>X-Accel-Redirect</header>,
<header>X-Accel-Expires</header>, <header>X-Accel-Limit-Rate</header> (1.1.6),
<header>X-Accel-Buffering</header> (1.1.6),
<header>X-Accel-Charset</header> (1.1.6), <header>Expires</header>,
<header>Cache-Control</header>, and <header>Set-Cookie</header> (0.8.44).
</para>

</directive>


<directive name="proxy_intercept_errors">
<syntax><literal>on</literal> | <literal>off</literal></syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Determines whether proxied responses with codes greater than or equal
to 400 should be passed to a client or be redirected to nginx for processing
using the <link doc="ngx_http_core_module.xml" id="error_page"/> directive.
</para>

</directive>


<directive name="proxy_next_upstream">
<syntax>
  <literal>error</literal> |
  <literal>timeout</literal> |
  <literal>invalid_header</literal> |
  <literal>http_500</literal> |
  <literal>http_502</literal> |
  <literal>http_503</literal> |
  <literal>http_504</literal> |
  <literal>http_404</literal> |
  <literal>off</literal>
  ...</syntax>
<default>error timeout</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Specifies in which cases a request should be passed to the next server:
<list type="tag">

<tag-name><literal>error</literal></tag-name>
<tag-desc>an error occurred while establishing a connection with the
server, passing it a request, or reading the response header;</tag-desc>

<tag-name><literal>timeout</literal></tag-name>
<tag-desc>a timeout has occurred while establishing a connection with the
server, passing it a request, or reading the response header;</tag-desc>

<tag-name><literal>invalid_header</literal></tag-name>
<tag-desc>a server returned empty or invalid response;</tag-desc>

<tag-name><literal>http_500</literal></tag-name>
<tag-desc>a server returned a response with the code 500;</tag-desc>

<tag-name><literal>http_502</literal></tag-name>
<tag-desc>a server returned a response with the code 502;</tag-desc>

<tag-name><literal>http_503</literal></tag-name>
<tag-desc>a server returned a response with the code 503;</tag-desc>

<tag-name><literal>http_504</literal></tag-name>
<tag-desc>a server returned a response with the code 504;</tag-desc>

<tag-name><literal>http_404</literal></tag-name>
<tag-desc>a server returned a response with the code 404;</tag-desc>

<tag-name><literal>off</literal></tag-name>
<tag-desc>disables passing a request to the next server.</tag-desc>

</list>
</para>

<para>
It should be understood that passing a request to the next server is
only possible if a client was not sent anything yet.
That is, if an error or a timeout occurs in the middle of
transferring a response, fixing this is impossible.
</para>

</directive>


<directive name="proxy_no_cache">
<syntax><value>string</value> ...</syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Defines conditions under which the response will not be saved to a cache.
If at least one value of the string parameters is not empty and is not
equal to “0” then the response will not be saved:
<example>
proxy_no_cache $cookie_nocache $arg_nocache$arg_comment;
proxy_no_cache $http_pragma    $http_authorization;
</example>
Can be used along with the <link id="proxy_cache_bypass"/> directive.
</para>

</directive>


<directive name="proxy_pass">
<syntax><value>URL</value></syntax>
<default/>
<context>location</context>
<context>if in location</context>
<context>limit_except</context>

<para>
Sets an address of the proxied server and a URI that maps a location.
An address can be specified as a domain name or an address, and a port,
for example,
<example>
proxy_pass http://localhost:8000/uri/;
</example>
or as a UNIX-domain socket path:
<example>
proxy_pass http://unix:/tmp/backend.socket:/uri/;
</example>
here a path is specified after the word “<literal>unix</literal>”
and enclosed in two colons.
</para>

<para>
If a domain name resolves to several addresses, all of them will be
used in a round-robin fashion.
In addition, an address can be specified as a
<link doc="ngx_http_upstream_module.xml">server group</link>.
</para>

<para>
When passing a request to the server, part of a URI matching the location
is replaced by a URI specified in the <literal>proxy_pass</literal> directive.
This rule has two exceptions where a replacement location cannot be
defined:
<list type="bullet">

<listitem>
when a location is specified using a regular expression;
</listitem>

<listitem>
if a URI is changed using the
<link doc="ngx_http_rewrite_module.xml" id="rewrite"/> directive
inside a proxied location, and this same configuration will be
used to process a request (<literal>break</literal>):
<example>
location /name/ {
    rewrite    /name/([^/]+) /users?name=$1 break;
    proxy_pass http://127.0.0.1;
}
</example>
In these cases a URI is passed without mapping.
</listitem>

</list>
</para>

<para>
It can also be specified that a request URI should be passed unchanged,
in the same form it was sent by the client, not the processed form.
During a processing
<list type="bullet">

<listitem>
two or more adjacent slashes are replaced by one: “//” — “/”;
</listitem>

<listitem>
links to the current directory get removed: “/./” — “/”;
</listitem>

<listitem>
links to the parent directory get removed: “/dir/../” — “/”.
</listitem>

</list>
</para>

<para>
If a URI should be passed unchanged then the server URL should be specified
without a URI in the <literal>proxy_pass</literal> directive:
<example>
location /some/path/ {
    proxy_pass http://127.0.0.1;
}
</example>
</para>

<para>
Server name, its port, and passed URI can be specified using variables:
<example>
proxy_pass http://$host$uri;
</example>
or like this:
<example>
proxy_pass $request;
</example>
</para>

<para>
In this case the server name is searched among the described
<link doc="ngx_http_upstream_module.xml">server groups</link>,
and if not found is determined using a
<link doc="ngx_http_core_module.xml" id="resolver"/>.
</para>

</directive>


<directive name="proxy_pass_header">
<syntax><value>field</value></syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Permits to pass <link id="proxy_hide_header">otherwise disabled</link> header
fields from a proxied server to a client.
</para>

</directive>


<directive name="proxy_read_timeout">
<syntax><value>time</value></syntax>
<default>60s</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Defines a timeout for reading a response from the proxied server.
A timeout is only set between two successive read operations,
not for the transmission of the whole response.
If a proxied server does not transmit anything within this time,
a connection is closed.
</para>

</directive>


<directive name="proxy_redirect">
<syntax><literal>default</literal></syntax>
<syntax><literal>off</literal></syntax>
<syntax><value>redirect</value> <value>replacement</value></syntax>
<default>default</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets a text that should be changed in the header fields
<header>Location</header> and <header>Refresh</header> of a response
from the proxied server.
Suppose a proxied server returned the header field
“<literal>Location: http://localhost:8000/two/some/uri/</literal>”.
The directive
<example>
proxy_redirect http://localhost:8000/two/ http://frontend/one/;
</example>
will rewrite this string to
“<literal>Location: http://frontend/one/some/uri/</literal>”.
</para>

<para>
A server name may be omitted from the <value>replacement</value> string:
<example>
proxy_redirect http://localhost:8000/two/ /;
</example>
then the primary server’s name and a port, if different from 80,
will be substituted.
</para>

<para>
The default replacement specified by the <literal>default</literal> parameter
uses the parameters of the
<link doc="ngx_http_core_module.xml" id="location"/> and
<link id="proxy_pass"/> directives.
Hence, the two configurations below are equivalent:
<example>
location /one/ {
    proxy_pass     http://upstream:port/two/;
    proxy_redirect default;
</example>

<example>
location /one/ {
    proxy_pass     http://upstream:port/two/;
    proxy_redirect http://upstream:port/two/ /one/;
</example>
The <literal>default</literal> parameter is not permitted if
<link id="proxy_pass"/> is specified using variables.
</para>

<para>
A <value>replacement</value> string can contain variables:
<example>
proxy_redirect http://localhost:8000/ http://$host:$server_port/;
</example>
</para>

<para>
A <value>redirect</value> can also contain (1.1.11) variables:
<example>
proxy_redirect http://$proxy_host:8000/ /;
</example>
</para>

<para>
A directive can be specified (1.1.11) using regular expressions.
In this case, <value>replacement</value> should either start from
the “<literal>~</literal>” symbol for a case-sensitive matching,
or from the “<literal>~*</literal>” symbols for case-insensitive
matching.
A regular expression can contain named and positional captures,
and <value>replacement</value> can reference them:
<example>
proxy_redirect ~^(http://[^:]+):\d+(/.+)$ $1$2;
proxy_redirect ~*/user/([^/]+)/(.+)$      http://$1.example.com/$2;
</example>
</para>

<para>
There could be several <literal>proxy_redirect</literal> directives:
<example>
proxy_redirect default;
proxy_redirect http://localhost:8000/  /;
proxy_redirect http://www.example.com/ /;
</example>
</para>

<para>
The <literal>off</literal> parameter cancels all
<literal>proxy_redirect</literal> directives on the current level:
<example>
proxy_redirect off;
proxy_redirect default;
proxy_redirect http://localhost:8000/  /;
proxy_redirect http://www.example.com/ /;
</example>
</para>

<para>
Using this directive it is also possible to add host names to relative
redirects issued by a proxied server:
<example>
proxy_redirect / /;
</example>
</para>

</directive>


<directive name="proxy_send_timeout">
<syntax><value>time</value></syntax>
<default>60s</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets a timeout for transmitting a request to the proxied server.
A timeout is only set between two successive write operations,
not for the transmission of the whole request.
If a proxied server does not receive anything within this time,
a connection is closed.
</para>

</directive>


<directive name="proxy_set_header">
<syntax><value>field</value> <value>value</value></syntax>
<default>Host $proxy_host</default>
<default>Connection close</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Allows to redefine or append fields to the request header
passed to the proxied server.
A <value>value</value> can contain text, variables, and their combination.
These directives are inherited from the previous level if and
only if there are no
<literal>proxy_set_header</literal>
directives defined on the current level.
By default, only two fields are redefined:
<example>
proxy_set_header Host       $proxy_host;
proxy_set_header Connection close;
</example>
</para>

<para>
An unchanged <header>Host</header> request header field can be passed like this:
<example>
proxy_set_header Host       $http_host;
</example>
</para>

<para>
However, if this field is not present in a client request header then
nothing will be passed.
In such a case it is better to use the <var>$host</var> variable&mdash;its
value equals the server name in the <header>Host</header> request header
field, or the primary server name if this field is not present:
<example>
proxy_set_header Host       $host;
</example>
</para>

<para>
In addition, a server name can be passed together with a port of the
proxied server:
<example>
proxy_set_header Host       $host:$proxy_port;
</example>
</para>

<para>
If the value of a header field is an empty string then this
field will not be passed to a proxied server:
<example>
proxy_set_header Accept-Encoding "";
</example>
</para>

</directive>


<directive name="proxy_ssl_session_reuse">
<syntax><literal>on</literal> | <literal>off</literal></syntax>
<default>on</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Determines whether SSL sessions can be reused when working with
the proxied server.
If the errors
“<literal>SSL3_GET_FINISHED:digest check failed</literal>”
appear in the logs, try to disable session reuse.
</para>

</directive>


<directive name="proxy_store">
<syntax>
    <literal>on</literal> |
    <literal>off</literal> |
    <value>string</value></syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Enables saving of files to a disk.
The <literal>on</literal> parameter saves files with paths
corresponding to the directives
<link doc="ngx_http_core_module.xml" id="alias"/> or
<link doc="ngx_http_core_module.xml" id="root"/>.
The <literal>off</literal> parameter disables saving of files.
In addition, the file name can be set explicitly using the
<value>string</value> with variables:
<example>
proxy_store /data/www$original_uri;
</example>
</para>

<para>
The modification time of files is set according to the received
<header>Last-Modified</header> response header field.
A response is first written to a temporary file, then a file is renamed.
Starting from version 0.8.9 temporary files and the persistent store
can be put on different file systems but be aware that in this case
a file is copied across two file systems instead of the cheap rename operation.
It is thus recommended that for any given location both saved files and a
directory holding temporary files set by the <link id="proxy_temp_path"/>
directive are put on the same file system.
</para>

<para>
This directive can be used to create local copies of static unchangeable
files, e.g.:
<example>
location /images/ {
    root                   /data/www;
    open_file_cache_errors off;
    error_page             404 = /fetch$uri;
}

location /fetch/ {
    internal;

    proxy_pass             http://backend/;
    proxy_store            on;
    proxy_store_access     user:rw group:rw all:r;
    proxy_temp_path        /data/temp;

    alias                  /data/www/;
}
</example>
</para>

<para>
or like this:
<example>
location /images/ {
    root               /data/www;
    error_page         404 = @fetch;
}

location @fetch {
    internal;

    proxy_pass         http://backend;
    proxy_store        on;
    proxy_store_access user:rw group:rw all:r;
    proxy_temp_path    /data/temp;

    root               /data/www;
}
</example>
</para>

</directive>


<directive name="proxy_store_access">
<syntax><value>users</value>:<value>permissions</value> ...</syntax>
<default>user:rw</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets access permissions for newly created files and directories, e.g.:
<example>
proxy_store_access user:rw group:rw all:r;
</example>
</para>

<para>
If any <literal>group</literal> or <literal>all</literal> access permissions
are specified then <literal>user</literal> permissions may be omitted:
<example>
proxy_store_access group:rw all:r;
</example>
</para>

</directive>


<directive name="proxy_temp_path">
<syntax>
    <value>path</value>
    [<value>level1</value>
    [<value>level2</value>
    [<value>level3</value>]]]</syntax>
<default>proxy_temp</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Defines a directory for storing temporary files
received from another server.
Up to three-level subdirectory hierarchy can be used underneath the specified
directory.
For example, in the following configuration
<example>
proxy_temp_path /spool/nginx/proxy_temp 1 2;
</example>
a temporary file might look like this:
<example>
/spool/nginx/proxy_temp/<emphasis>7</emphasis>/<emphasis>45</emphasis>/00000123<emphasis>457</emphasis>
</example>
</para>

</directive>

</section>


<section id="variables" name="Embedded Variables">

<para>
The <literal>ngx_http_proxy_module</literal> module supports embedded variables
that can be used to compose headers using the
<link id="proxy_set_header"/> directive:
<list type="tag">

<tag-name><var>$proxy_host</var></tag-name>
<tag-desc>name and port of a proxied server;</tag-desc>

<tag-name><var>$proxy_port</var></tag-name>
<tag-desc>port of a proxied server;</tag-desc>

<tag-name><var>$proxy_add_x_forwarded_for</var></tag-name>
<tag-desc>the <header>X-Forwarded-For</header> client request header field
with the <var>$remote_addr</var> variable appended to it, separated by a comma.
If the <header>X-Forwarded-For</header> field is not present in the client
request header, the <var>$proxy_add_x_forwarded_for</var> variable is equal
to the <var>$remote_addr</var> variable.</tag-desc>
</list>
</para>

</section>

</module>