The ngx_http_proxy_module module allows to pass requests to another server.

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

proxy_buffer_size 4k|8k;

Sets size 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 proxy_buffers directive. It can be made smaller however.

proxy_buffering on;

Enables or disables buffering of responses from the proxied server.

When buffering is enabled, nginx receives a response from the proxied server as soon as possible, saving it into buffers set by the proxy_buffer_size and proxy_buffers directives. If the whole response does not fit into memory, part of it can be saved to a temporary file on disk. Writes to temporary files are controlled by the proxy_max_temp_file_size and proxy_temp_file_write_size directives.

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 proxy_buffer_size directive.

proxy_buffers 8 4k|8k;

Sets the number and size 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.

proxy_busy_buffers_size 8k|16k;

When buffering of responses from the proxied server is enabled, limits the total size 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, size is limited by two buffers set by the proxy_buffer_size and proxy_buffers directives.

proxy_cache off;

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

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:

proxy_cache_bypass $cookie_nocache $arg_nocache$arg_comment;
proxy_cache_bypass $http_pragma    $http_authorization;

Can be used along with the proxy_no_cache directive.

proxy_cache_key $scheme$proxy_host$request_uri;

Defines a key for caching, for example

proxy_cache_key "$host$request_uri $cookie_user";

By default, the directive’s value is close to the string

proxy_cache_key $scheme$proxy_host$uri$is_args$args;

proxy_cache_lock off;

When enabled, only one request at a time will be allowed to populate a new cache element identified according to the 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 proxy_cache_lock_timeout directive.

proxy_cache_lock_timeout 5s;

Sets a timeout for proxy_cache_lock.

proxy_cache_min_uses 1;

Sets the number of requests after which the response will be cached.

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 levels parameter defines hierarchy levels of a cache. For example, in the following configuration

proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=one:10m;

file names in a cache will look like this:

/data/nginx/cache/c/29/b7f54b2df7773722d382f4809d65029c

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 proxy_temp_path directive are put on the same file system.

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

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

proxy_cache_use_stale off;

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 proxy_next_upstream directive. Additionally, the updating parameter permits to use a stale cached response if it is currently being updated.

Sets caching time for different response codes. For example, the following directives

proxy_cache_valid 200 302 10m;
proxy_cache_valid 404      1m;

set 10 minutes of caching for responses with codes 200 and 302, and 1 minute for responses with code 404.

If only caching time is specified

proxy_cache_valid 5m;

then only 200, 301, and 302 responses are cached.

In addition, it can be specified to cache any responses using the any parameter:

proxy_cache_valid 200 302 10m;
proxy_cache_valid 301      1h;
proxy_cache_valid any      1m;

proxy_connect_timeout 60s;

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

proxy_cookie_domain off;

Sets a text that should be changed in the domain attribute of the “Set-Cookie” header fields of a proxied server response. Suppose a proxied server returned the header field “Set-Cookie” with the attribute “domain=localhost”. The directive

proxy_cookie_domain localhost example.org;

will rewrite this attribute to “domain=example.org”.

A dot at the beginning of the domain and replacement strings, and the domain attribute is ignored. Matching is case-insensitive.

The strings domain and replacement can contain variables:

proxy_cookie_domain www.$host $host;

A directive can also be specified using regular expressions. In this case, domain should start from the “~” symbol. A regular expression can contain named and positional captures, and replacement can reference them:

proxy_cookie_domain ~\.(?P<sl_domain>[-0-9a-z]+\.[a-z]+)$ $sl_domain;

There could be several proxy_cookie_domain directives:

proxy_cookie_domain localhost example.org;
proxy_cookie_domain ~\.([a-z]+\.[a-z]+)$ $1;

The off parameter cancels all proxy_cookie_domain directives on the current level:

proxy_cookie_domain off;
proxy_cookie_domain localhost example.org;
proxy_cookie_domain www.example.org example.org;

proxy_cookie_path off;

Sets a text that should be changed in the path attribute of the “Set-Cookie” header fields of a proxied server response. Suppose a proxied server returned the header field “Set-Cookie” with the attribute “path=/two/some/uri/”. The directive

proxy_cookie_path /two/ /;

will rewrite this attribute to “path=/some/uri/”.

The strings path and replacement can contain variables:

proxy_cookie_path $uri /some$uri;

A directive can also be specified using regular expressions. In this case, path should either start from the “~” symbol for a case-sensitive matching, or from the “~*” symbols for case-insensitive matching. A regular expression can contain named and positional captures, and replacement can reference them:

proxy_cookie_path ~*^/user/([^/]+) /u/$1;

There could be several proxy_cookie_path directives:

proxy_cookie_path /one/ /;
proxy_cookie_path / /two/;

The off parameter cancels all proxy_cookie_path directives on the current level:

proxy_cookie_path off;
proxy_cookie_path /two/ /;
proxy_cookie_path ~*^/user/([^/]+) /u/$1;

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

proxy_http_version 1.0;

Sets the HTTP protocol version for proxying. By default, version 1.0 is used. Version 1.1 is recommended for use with keepalive connections.

proxy_ignore_client_abort off;

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

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

proxy_intercept_errors off;

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 error_page directive.

proxy_max_temp_file_size 1024m;

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

Value of zero disables buffering of responses to temporary files.

proxy_next_upstream error timeout;

Specifies in which cases a request should be passed to the next server:

error

an error occurred while establishing a connection with the server, passing it a request, or reading the response header;

timeout

a timeout has occurred while establishing a connection with the server, passing it a request, or reading the response header;

invalid_header

a server returned empty or invalid response;

http_500

a server returned a response with the code 500;

http_502

a server returned a response with the code 502;

http_503

a server returned a response with the code 503;

http_504

a server returned a response with the code 504;

http_404

a server returned a response with the code 404;

off

disables passing a request to the next server.

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.

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:

proxy_no_cache $cookie_nocache $arg_nocache$arg_comment;
proxy_no_cache $http_pragma    $http_authorization;

Can be used along with the proxy_cache_bypass directive.

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,

proxy_pass http://localhost:8000/uri/;

or as a UNIX-domain socket path:

proxy_pass http://unix:/tmp/backend.socket:/uri/;

here a path is specified after the word “unix” and enclosed in two colons.

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 server group.

When passing a request to the server, part of a URI matching the location is replaced by a URI specified in the proxy_pass directive. This rule has two exceptions where a replacement location cannot be defined:

• when a location is specified using a regular expression;
• if a URI is changed using the rewrite directive inside a proxied location, and this same configuration will be used to process a request (break):

  location /name/ {
      rewrite    /name/([^/]+) /users?name=$1 break;
      proxy_pass http://127.0.0.1;
  }
  

  In these cases a URI is passed without mapping.

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

• two or more adjacent slashes are replaced by one: “//” — “/”;
• links to the current directory get removed: “/./” — “/”;
• links to the parent directory get removed: “/dir/../” — “/”.

If a URI should be passed unchanged then the server URL should be specified without a URI in the proxy_pass directive:

location /some/path/ {
    proxy_pass http://127.0.0.1;
}

Server name, its port, and passed URI can be specified using variables:

proxy_pass http://$host$uri;

or like this:

proxy_pass $request;

In this case the server name is searched among the described server groups, and if not found is determined using a resolver.

Permits to pass otherwise disabled header fields from a proxied server to a client.

proxy_read_timeout 60s;

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.

proxy_redirect default;

Sets a text that should be changed in the header fields “Location” and “Refresh” of a response from the proxied server. Suppose a proxied server returned the header field “Location: http://localhost:8000/two/some/uri/”. The directive

proxy_redirect http://localhost:8000/two/ http://frontend/one/;

will rewrite this string to “Location: http://frontend/one/some/uri/”.

A server name may be omitted from the replacement string:

proxy_redirect http://localhost:8000/two/ /;

then the primary server’s name and a port, if different from 80, will be substituted.

The default replacement specified by the default parameter uses the parameters of the location and proxy_pass directives. Hence, the two configurations below are equivalent:

location /one/ {
    proxy_pass     http://upstream:port/two/;
    proxy_redirect default;

location /one/ {
    proxy_pass     http://upstream:port/two/;
    proxy_redirect http://upstream:port/two/ /one/;

The default parameter is not permitted if proxy_pass is specified using variables.

A replacement string can contain variables:

proxy_redirect http://localhost:8000/ http://$host:$server_port/;

A redirect can also contain (1.1.11) variables:

proxy_redirect http://$proxy_host:8000/ /;

A directive can be specified (1.1.11) using regular expressions. In this case, redirect should either start from the “~” symbol for a case-sensitive matching, or from the “~*” symbols for case-insensitive matching. A regular expression can contain named and positional captures, and replacement can reference them:

proxy_redirect ~^(http://[^:]+):\d+(/.+)$ $1$2;
proxy_redirect ~*/user/([^/]+)/(.+)$      http://$1.example.com/$2;

There could be several proxy_redirect directives:

proxy_redirect default;
proxy_redirect http://localhost:8000/  /;
proxy_redirect http://www.example.com/ /;

The off parameter cancels all proxy_redirect directives on the current level:

proxy_redirect off;
proxy_redirect default;
proxy_redirect http://localhost:8000/  /;
proxy_redirect http://www.example.com/ /;

Using this directive it is also possible to add host names to relative redirects issued by a proxied server:

proxy_redirect / /;

proxy_send_timeout 60s;

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.

proxy_set_header Host $proxy_host;

proxy_set_header Connection close;

Allows to redefine or append fields to the request header passed to the proxied server. A value can contain text, variables, and their combination. These directives are inherited from the previous level if and only if there are no proxy_set_header directives defined on the current level. By default, only two fields are redefined:

proxy_set_header Host       $proxy_host;
proxy_set_header Connection close;

An unchanged “Host” request header field can be passed like this:

proxy_set_header Host       $http_host;

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 $host variable - its value equals the server name in the “Host” request header field, or the primary server name if this field is not present:

proxy_set_header Host       $host;

In addition, a server name can be passed together with a port of the proxied server:

proxy_set_header Host       $host:$proxy_port;

If the value of a header field is an empty string then this field will not be passed to a proxied server:

proxy_set_header Accept-Encoding "";

proxy_ssl_session_reuse on;

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

proxy_store off;

Enables saving of files to a disk. The on parameter saves files with paths corresponding to the directives alias or root. The off parameter disables saving of files. In addition, the file name can be set explicitly using the string with variables:

proxy_store /data/www$original_uri;

The modification time of files is set according to the received “Last-Modified” 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 proxy_temp_path directive are put on the same file system.

This directive can be used to create local copies of static unchangeable files, e.g.:

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/;
}

or like this:

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;
}

proxy_store_access user:rw;

Sets access permissions for newly created files and directories, e.g.:

proxy_store_access user:rw group:rw all:r;

If any group or all access permissions are specified then user permissions may be omitted:

proxy_store_access group:rw all:r;

proxy_temp_file_write_size 8k|16k;

Limits the size 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, size is limited by two buffers set by the proxy_buffer_size and proxy_buffers directives. The maximum size of a temporary file is set by the proxy_max_temp_file_size directive.

proxy_temp_path proxy_temp;

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

proxy_temp_path /spool/nginx/proxy_temp 1 2;

a temporary file might look like this:

/spool/nginx/proxy_temp/7/45/00000123457

The ngx_http_proxy_module module supports embedded variables that can be used to compose headers using the proxy_set_header directive:

$proxy_host

name and port of a proxied server;

$proxy_port

port of a proxied server;

$proxy_add_x_forwarded_for

the “X-Forwarded-For” client request header field with the $remote_addr variable appended to it, separated by a comma. If the “X-Forwarded-For” field is not present in the client request header, the $proxy_add_x_forwarded_for variable is equal to the $remote_addr variable.