<?xml version="1.0"?>

<!--
  Copyright (C) Igor Sysoev
  Copyright (C) Nginx, Inc.
  -->

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

<module name="Module ngx_http_proxy_module"
        link="/en/docs/http/ngx_http_proxy_module.html"
        lang="en"
        rev="17">

<section id="summary">

<para>
The <literal>ngx_http_proxy_module</literal> module allows passing
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_bind">
<syntax><value>address</value> | <literal>off</literal></syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>0.8.22</appeared-in>

<para>
Makes outgoing connections to a proxied server originate
from the specified local IP <value>address</value>.
Parameter value can contain variables (1.3.12).
The special value <literal>off</literal> (1.3.12) cancels the effect
of the <literal>proxy_bind</literal> directive
inherited from the previous configuration level, which allows the
system to auto-assign the local IP address.
</para>

</directive>


<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 the <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 of responses 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 the buffers set by the
<link id="proxy_buffer_size"/> and <link id="proxy_buffers"/> directives.
If the whole response does not fit into memory, a part of it can be saved
to a <link id="proxy_temp_path">temporary file</link> on the disk.
Writing to temporary files is controlled by the
<link id="proxy_max_temp_file_size"/> and
<link id="proxy_temp_file_write_size"/> directives.
</para>

<para>
When buffering is disabled, a response is passed to a client synchronously,
immediately as it is received.
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>

<para>
Buffering can also be enabled or disabled by passing
“<literal>yes</literal>” or “<literal>no</literal>” in the
<header>X-Accel-Buffering</header> response header field.
This capability can be disabled using the
<link id="proxy_ignore_headers"/> 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_busy_buffers_size">
<syntax><value>size</value></syntax>
<default>8k|16k</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
When <link id="proxy_buffering">buffering</link> of responses from the proxied
server is enabled, limits the total <value>size</value> of buffers that
can be busy sending a response to the client while the response is not
yet fully read.
In the mean time, the rest of the buffers can be used for reading a response
and, if needed, buffering part of a response to a temporary file.
By default, <value>size</value> is limited by the size of two buffers set by the
<link id="proxy_buffer_size"/> and <link id="proxy_buffers"/> directives.
</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 shared memory 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_methods">
<syntax>
    <literal>GET</literal> |
    <literal>HEAD</literal> |
    <literal>POST</literal>
    ...</syntax>
<default>GET HEAD</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>0.7.59</appeared-in>

<para>
If the client request method is listed in this directive then
the response will be cached.
“<literal>GET</literal>” and “<literal>HEAD</literal>” methods are always
added to the list, though it is recommended to specify them explicitly.
See also the <link id="proxy_no_cache"/> directive.
</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>]
    [<literal>loader_files</literal>=<value>number</value>]
    [<literal>loader_sleep</literal>=<value>time</value>]
    [<literal>loader_threshold</literal>=<value>time</value>]</syntax>
<default/>
<context>http</context>

<para>
Sets the 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,
and then the file is renamed.
Starting from version 0.8.9, temporary files and the cache can be put on
different file systems.
However, be aware that in this case a file is copied
across two file systems instead of the cheap renaming 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 “cache manager” process 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>

<para>
A minute after the start the special “cache loader” process is activated.
It loads information about previously cached data stored on file system
into a cache zone.
The loading is done in iterations.
During one iteration no more than <literal>loader_files</literal> items
are loaded (by default, 100).
Besides, the duration of one iteration is limited by the
<literal>loader_threshold</literal> parameter (by default, 200 milliseconds).
Between iterations, a pause configured by the <literal>loader_sleep</literal>
parameter (by default, 50 milliseconds) is made.
</para>

</directive>


<directive name="proxy_cache_purge">
<syntax>string ...</syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.5.7</appeared-in>

<para>
Defines conditions under which the request will be considered a cache
purge request.
If at least one value of the string parameters is not empty and is not equal
to “0” then the cache entry with a corresponding
<link id="proxy_cache_key">cache key</link> is removed.
The result of successful operation is indicated by returning
the <http-status code="204" text="No Content"/> response.
</para>

<para>
If the <link id="proxy_cache_key">cache key</link> of a purge request ends
with an asterisk (“<literal>*</literal>”), all cache entries matching the
wildcard key will be removed from the cache.
</para>

<para>
Example configuration:
<example>
proxy_cache_path /data/nginx/cache keys_zone=cache_zone:10m;

map $request_method $purge_method {
    PURGE   1;
    default 0;
}

server {
    ...
    location / {
        proxy_pass http://backend;
        proxy_cache cache_zone;
        proxy_cache_key $uri;
        proxy_cache_purge $purge_method;
    }
}
</example>
<note>
This functionality is available as part of our <commercial_version/> only.
</note>
</para>

</directive>


<directive name="proxy_cache_revalidate">
<syntax><literal>on</literal> | <literal>off</literal></syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.5.7</appeared-in>

<para>
Enables revalidation of expired cache items using conditional requests with
the <header>If-Modified-Since</header> header field.
</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_403</literal> |
    <literal>http_404</literal> |
    <literal>off</literal>
    ...</syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Determines in which cases a stale cached response can be used
when an error occurs during communication with the proxied server.
The directive’s parameters match the parameters of the
<link id="proxy_next_upstream"/> directive.
</para>

<para>
Additionally, the <literal>updating</literal> parameter permits
using a stale cached response if it is currently being updated.
This allows minimizing the number of accesses to proxied servers
when updating cached data.
</para>

<para>
To minimize the number of accesses to proxied servers when
populating a new cache element, the <link id="proxy_cache_lock"/>
directive can be used.
</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, the <literal>any</literal> parameter can be specified
to cache any responses:
<example>
proxy_cache_valid 200 302 10m;
proxy_cache_valid 301      1h;
proxy_cache_valid any      1m;
</example>
</para>

<para>
Parameters of caching can also be set directly
in the response header.
This has higher priority than setting of caching time using the directive.
The <header>X-Accel-Expires</header> header field sets caching time of a
response in seconds.
The zero value disables caching for a response.
If a value starts with the <literal>@</literal> prefix, it sets an absolute
time in seconds since Epoch, up to which the response may be cached.
If header does not include the <header>X-Accel-Expires</header> field,
parameters of caching may be set in the header fields
<header>Expires</header> or <header>Cache-Control</header>.
If a header includes the <header>Set-Cookie</header> field, such a
response will not be cached.
Processing of one or more of these response header fields can be disabled
using the <link id="proxy_ignore_headers"/> directive.
</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 a proxied server.
It should be noted that this timeout cannot usually exceed 75 seconds.
</para>

</directive>


<directive name="proxy_cookie_domain">
<syntax><literal>off</literal></syntax>
<syntax><value>domain</value> <value>replacement</value></syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.1.15</appeared-in>

<para>
Sets a text that should be changed in the <literal>domain</literal>
attribute of the <header>Set-Cookie</header> header fields of a
proxied server response.
Suppose a proxied server returned the <header>Set-Cookie</header>
header field with the attribute
“<literal>domain=localhost</literal>”.
The directive
<example>
proxy_cookie_domain localhost example.org;
</example>
will rewrite this attribute to
“<literal>domain=example.org</literal>”.
</para>

<para>
A dot at the beginning of the <value>domain</value> and
<value>replacement</value> strings and the <literal>domain</literal>
attribute is ignored.
Matching is case-insensitive.
</para>

<para>
The <value>domain</value> and <value>replacement</value> strings
can contain variables:
<example>
proxy_cookie_domain www.$host $host;
</example>
</para>

<para>
The directive can also be specified using regular expressions.
In this case, <value>domain</value> should start from
the “<literal>~</literal>” symbol.
A regular expression can contain named and positional captures,
and <value>replacement</value> can reference them:
<example>
proxy_cookie_domain ~\.(?P&lt;sl_domain&gt;[-0-9a-z]+\.[a-z]+)$ $sl_domain;
</example>
</para>

<para>
There could be several <literal>proxy_cookie_domain</literal> directives:
<example>
proxy_cookie_domain localhost example.org;
proxy_cookie_domain ~\.([a-z]+\.[a-z]+)$ $1;
</example>
</para>

<para>
The <literal>off</literal> parameter cancels the effect of all
<literal>proxy_cookie_domain</literal> directives on the current level:
<example>
proxy_cookie_domain off;
proxy_cookie_domain localhost example.org;
proxy_cookie_domain www.example.org example.org;
</example>
</para>

</directive>


<directive name="proxy_cookie_path">
<syntax><literal>off</literal></syntax>
<syntax><value>path</value> <value>replacement</value></syntax>
<default>off</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.1.15</appeared-in>

<para>
Sets a text that should be changed in the <literal>path</literal>
attribute of the <header>Set-Cookie</header> header fields of a
proxied server response.
Suppose a proxied server returned the <header>Set-Cookie</header>
header field with the attribute
“<literal>path=/two/some/uri/</literal>”.
The directive
<example>
proxy_cookie_path /two/ /;
</example>
will rewrite this attribute to
“<literal>path=/some/uri/</literal>”.
</para>

<para>
The <value>path</value> and <value>replacement</value> strings
can contain variables:
<example>
proxy_cookie_path $uri /some$uri;
</example>
</para>

<para>
The directive can also be specified using regular expressions.
In this case, <value>path</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_cookie_path ~*^/user/([^/]+) /u/$1;
</example>
</para>

<para>
There could be several <literal>proxy_cookie_path</literal> directives:
<example>
proxy_cookie_path /one/ /;
proxy_cookie_path / /two/;
</example>
</para>

<para>
The <literal>off</literal> parameter cancels the effect of all
<literal>proxy_cookie_path</literal> directives on the current level:
<example>
proxy_cookie_path off;
proxy_cookie_path /two/ /;
proxy_cookie_path ~*^/user/([^/]+) /u/$1;
</example>
</para>

</directive>


<directive name="proxy_headers_hash_bucket_size">
<syntax><value>size</value></syntax>
<default>64</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets the bucket <value>size</value> for hash tables
used by the <link id="proxy_hide_header"/> and <link id="proxy_set_header"/>
directives.
The details of setting up hash tables are provided in a separate
<link doc="../hash.xml">document</link>.
</para>

</directive>


<directive name="proxy_headers_hash_max_size">
<syntax><value>size</value></syntax>
<default>512</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Sets the maximum <value>size</value> of hash tables
used by the <link id="proxy_hide_header"/> and <link id="proxy_set_header"/>
directives.
The details of setting up hash tables are provided in a separate
<link doc="../hash.xml">document</link>.
</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 whether the connection with a proxied server should be
closed when 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>

<para>
If not disabled, processing of these header fields has the following
effect:
<list type="bullet" compact="no">

<listitem>
<header>X-Accel-Expires</header>, <header>Expires</header>,
<header>Cache-Control</header>, and <header>Set-Cookie</header>
set the parameters of response <link id="proxy_cache_valid">caching</link>;
</listitem>

<listitem>
<header>X-Accel-Redirect</header> performs an
<link doc="ngx_http_core_module.xml" id="internal">internal
redirect</link> to the specified URI;
</listitem>

<listitem>
<header>X-Accel-Limit-Rate</header> sets the
<link doc="ngx_http_core_module.xml" id="limit_rate">rate
limit</link> for transmission of a response to a client;
</listitem>

<listitem>
<header>X-Accel-Buffering</header> enables or disables
<link id="proxy_buffering">buffering</link> of a response;
</listitem>

<listitem>
<header>X-Accel-Charset</header> sets the desired
<link doc="ngx_http_charset_module.xml" id="charset"/>
of a response.
</listitem>

</list>
</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 300 should be passed to a client or be redirected to nginx for processing
with the <link doc="ngx_http_core_module.xml" id="error_page"/> directive.
</para>

</directive>


<directive name="proxy_max_temp_file_size">
<syntax><value>size</value></syntax>
<default>1024m</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
When <link id="proxy_buffering">buffering</link> of responses from the proxied
server is enabled, and the whole response does not fit into the memory buffers
set by the <link id="proxy_buffer_size"/> and <link id="proxy_buffers"/>
directives, a part of the response can be saved to a temporary file.
This directive sets the maximum <value>size</value> of a temporary file.
The size of data written to a temporary file at a time is set
by the <link id="proxy_temp_file_write_size"/> directive.
</para>

<para>
The zero value disables buffering of responses to temporary files.
</para>

</directive>


<directive name="proxy_method">
<syntax><value>method</value></syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Specifies the HTTP <value>method</value> to use in requests forwarded
to the proxied server instead of the method from the client request.
</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_403</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 a request to it, 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 a request to it, or reading the response header;</tag-desc>

<tag-name><literal>invalid_header</literal></tag-name>
<tag-desc>a server returned an 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_403</literal></tag-name>
<tag-desc>a server returned a response with the code 403;</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>
One should bear in mind that passing a request to the next server is
only possible if nothing has been sent to a client yet.
That is, if an error or timeout occurs in the middle of the
transferring of a response, fixing this is impossible.
</para>

<para>
The directive also defines what is considered an unsuccessful attempt
of communication with a
<link doc="ngx_http_upstream_module.xml" id="server"/>.
The cases of <literal>error</literal>, <literal>timeout</literal> and
<literal>invalid_header</literal> are always considered unsuccessful attempts,
even if they are not specified in the directive.
The cases of <literal>http_500</literal>, <literal>http_502</literal>,
<literal>http_503</literal> and <literal>http_504</literal> are
considered unsuccessful attempts only if they are specified in the directive.
The cases of <literal>http_403</literal> and <literal>http_404</literal>
are never considered unsuccessful attempts.
</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 the protocol and address of a proxied server and an optional URI
to which a location should be mapped.
As a protocol, “<literal>http</literal>” or “<literal>https</literal>”
can be specified.
The address can be specified as a domain name or IP address,
and an optional port:
<example>
proxy_pass http://localhost:8000/uri/;
</example>
or as a UNIX-domain socket path specified after the word
“<literal>unix</literal>” and enclosed in colons:
<example>
proxy_pass http://unix:/tmp/backend.socket:/uri/;
</example>
</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>
A request URI is passed to the server as follows:
<list type="bullet" compact="no">

<listitem>
If the <literal>proxy_pass</literal> directive is specified with a URI,
then when a request is passed to the server, the part of a
<link doc="ngx_http_core_module.xml" id="location">normalized</link>
request URI matching the location is replaced by a URI
specified in the directive:
<example>
location /name/ {
    proxy_pass http://127.0.0.1/remote/;
}
</example>
</listitem>

<listitem>
If <literal>proxy_pass</literal> is specified without a URI,
the request URI is passed to the server in the same form
as sent by a client when the original request is processed,
or the full normalized request URI is passed
when processing the changed URI:
<example>
location /some/path/ {
    proxy_pass http://127.0.0.1;
}
</example>
<note>
Before version 1.1.12,
if <literal>proxy_pass</literal> is specified without a URI,
the original request URI might be passed
instead of the changed URI in some cases.
</note>
</listitem>
</list>
</para>

<para>
In some cases, the part of a request URI to be replaced cannot be determined:
<list type="bullet" compact="no">

<listitem>
When location is specified using a regular expression.
<para>
In this case, the directive should be specified without a URI.
</para>
</listitem>

<listitem>
When the URI is changed inside a proxied location using the
<link doc="ngx_http_rewrite_module.xml" id="rewrite"/> directive,
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>
<para>
In this case, the URI specified in the directive is ignored and
the full changed request URI is passed to the server.
</para>
</listitem>
</list>
</para>

<para>
A server name, its port and the passed URI can also be specified using
variables:
<example>
proxy_pass http://$host$uri;
</example>
or even 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>

<para>
<link doc="websocket.xml">WebSocket</link> proxying requires special
configuration and is supported since version 1.3.13.
</para>

</directive>


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

<para>
Permits passing <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 set only 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_pass_request_body">
<syntax><literal>on</literal> | <literal>off</literal></syntax>
<default>on</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Indicates whether the original request body is passed
to the proxied server.
<example>
location /x-accel-redirect-here/ {
    proxy_method GET;
    proxy_pass_request_body off;
    proxy_set_header Content-Length "";

    proxy_pass ...
}
</example>
See also the <link id="proxy_set_header"/> and
<link id="proxy_pass_request_headers"/> directives.
</para>

</directive>


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

<para>
Indicates whether the header fields of the original request are passed
to the proxied server.
<example>
location /x-accel-redirect-here/ {
    proxy_method GET;
    proxy_pass_request_headers off;
    proxy_pass_request_body off;

    proxy_pass ...
}
</example>
See also the <link id="proxy_set_header"/> and
<link id="proxy_pass_request_body"/> directives.
</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 the text that should be changed in the <header>Location</header>
and <header>Refresh</header> header fields of a proxied server response.
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 in the <value>replacement</value> string:
<example>
proxy_redirect http://localhost:8000/two/ /;
</example>
then the primary server’s name and port, if different from 80,
will be inserted.
</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>
The directive can be specified (1.1.11) using regular expressions.
In this case, <value>redirect</value> should either start with
the “<literal>~</literal>” symbol for a case-sensitive matching,
or with 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 the effect of 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_lowat">
<syntax><value>size</value></syntax>
<default>0</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
If the directive is set to a non-zero value, nginx will try to
minimize the number
of send operations on outgoing connections to a proxied server by using either
<c-def>NOTE_LOWAT</c-def> flag of the
<link doc="../events.xml" id="kqueue"/> method,
or the <c-def>SO_SNDLOWAT</c-def> socket option,
with the specified <value>size</value>.
</para>

<para>
This directive is ignored on Linux, Solaris, and Windows.
</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 set only 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_body">
<syntax><value>value</value></syntax>
<default/>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Allows redefining the request body passed to the proxied server.
A <value>value</value> can contain text, variables, and their combination.
</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 redefining or appending fields to the request header
<link id="proxy_pass_request_headers">passed</link> to the proxied server.
A <value>value</value> can contain text, variables, and their combinations.
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, the server name can be passed together with the 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_ciphers">
<syntax><value>ciphers</value></syntax>
<default>DEFAULT</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.5.6</appeared-in>

<para>
Specifies the enabled ciphers for requests to a proxied HTTPS server.
The ciphers are specified in the format understood by the OpenSSL library.
</para>

<para>
The full list can be viewed using the
“<command>openssl ciphers</command>” command.
</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 disabling session reuse.
</para>

</directive>


<directive name="proxy_ssl_protocols">
<syntax>
    [<literal>SSLv2</literal>]
    [<literal>SSLv3</literal>]
    [<literal>TLSv1</literal>]
    [<literal>TLSv1.1</literal>]
    [<literal>TLSv1.2</literal>]</syntax>
<default>SSLv3 TLSv1 TLSv1.1 TLSv1.2</default>
<context>http</context>
<context>server</context>
<context>location</context>
<appeared-in>1.5.6</appeared-in>

<para>
Enables the specified protocols for requests to a proxied HTTPS server.
</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, and then the file is renamed.
Starting from version 0.8.9, temporary files and the persistent store
can be put on different file systems.
However, be aware that in this case a file is copied
across two file systems instead of the cheap renaming 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;
    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_file_write_size">
<syntax><value>size</value></syntax>
<default>8k|16k</default>
<context>http</context>
<context>server</context>
<context>location</context>

<para>
Limits the <value>size</value> of data written to a temporary file
at a time, when buffering of responses from the proxied server
to temporary files is enabled.
By default, <value>size</value> is limited by two buffers set by the
<link id="proxy_buffer_size"/> and <link id="proxy_buffers"/> directives.
The maximum size of a temporary file is set by the
<link id="proxy_max_temp_file_size"/> directive.
</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
with data received from proxied servers.
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>