The ngx_http_fastcgi_module module allows to pass requests to a FastCGI server.

location / {
    fastcgi_pass  localhost:9000;
    fastcgi_index index.php;

    fastcgi_param SCRIPT_FILENAME /home/www/scripts/php$fastcgi_script_name;
    fastcgi_param QUERY_STRING    $query_string;
    fastcgi_param REQUEST_METHOD  $request_method;
    fastcgi_param CONTENT_TYPE    $content_type;
    fastcgi_param CONTENT_LENGTH  $content_length;
}

fastcgi_buffer_size 4k|8k;

Sets size of the buffer used for reading the first part of a response received from the FastCGI 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 fastcgi_buffers directive. It can be made smaller however.

fastcgi_buffers 8 4k|8k;

Sets the number and size of buffers used for reading a response from the FastCGI 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.

fastcgi_busy_buffers_size 8k|16k;

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 fastcgi_buffer_size and fastcgi_buffers directives.

fastcgi_cache off;

Defines a shared memory 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:

fastcgi_cache_bypass $cookie_nocache $arg_nocache$arg_comment;
fastcgi_cache_bypass $http_pragma    $http_authorization;

Can be used along with the fastcgi_no_cache directive.

Defines a key for caching, for example

fastcgi_cache_key localhost:9000$request_uri;

fastcgi_cache_lock off;

When enabled, only one request at a time will be allowed to populate a new cache element identified according to the fastcgi_cache_key directive by passing a request to a FastCGI 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 fastcgi_cache_lock_timeout directive.

fastcgi_cache_lock_timeout 5s;

Sets a timeout for fastcgi_cache_lock.

fastcgi_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

fastcgi_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 fastcgi_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.

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

fastcgi_cache_use_stale off;

If an error occurs while working with the FastCGI 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 fastcgi_next_upstream directive.

Additionally, the updating parameter permits to use a stale cached response if it is currently being updated. This allows to minimize the number of accesses to FastCGI servers when updating cached data.

To minimize the number of accesses to FastCGI servers when populating a new cache element, the fastcgi_cache_lock directive can be used.

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

fastcgi_cache_valid 200 302 10m;
fastcgi_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

fastcgi_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:

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

Parameters of caching can also be set directly in the response header. This has a higher precedence than setting of caching time using the directive. The “X-Accel-Expires” header field sets caching time of a response in seconds. The value 0 disables to cache a response. If a value starts with the prefix @, it sets an absolute time in seconds since Epoch, up to which the response may be cached. If header does not include the “X-Accel-Expires” field, parameters of caching may be set in the header fields “Expires” or “Cache-Control”. If a header includes the “Set-Cookie” field, such a response will not be cached. Processing of one or more of these response header fields can be disabled using the fastcgi_ignore_headers directive.

fastcgi_connect_timeout 60s;

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

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

fastcgi_ignore_client_abort off;

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

Disables processing of certain response header fields from the FastCGI 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).

If not disabled, processing of these header fields has the following effect:

• “X-Accel-Expires”, “Expires”, “Cache-Control”, and “Set-Cookie” set parameters of response caching;
• “X-Accel-Redirect” performs an internal redirect to the specified URI;
• “X-Accel-Limit-Rate” sets a rate limit for transmission of a response to a client;
• “X-Accel-Buffering” enables or disables buffering of a response;
• “X-Accel-Charset” sets the desired charset of a response.

Sets a file name that will be appended after a URI that ends with a slash, in the value of the $fastcgi_script_name variable. For example, with these settings

fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME /home/www/scripts/php$fastcgi_script_name;

and the “/page.php” request, the SCRIPT_FILENAME parameter will be equal to “/home/www/scripts/php/page.php”, and with the “/” request it will be equal to “/home/www/scripts/php/index.php”.

fastcgi_intercept_errors off;

Determines whether FastCGI server 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.

fastcgi_keep_conn off;

By default, a FastCGI server will close a connection right after sending the response. When set to the value on, nginx will instruct a FastCGI server to keep connections open. This in particular is necessary for keepalive connections to FastCGI servers to function.

fastcgi_max_temp_file_size 1024m;

When the whole response does not fit into memory buffers set by the fastcgi_buffer_size and fastcgi_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 fastcgi_temp_file_write_size directive.

Value of zero disables buffering of responses to temporary files.

fastcgi_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_503

a server returned a response with the code 503;

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:

fastcgi_no_cache $cookie_nocache $arg_nocache$arg_comment;
fastcgi_no_cache $http_pragma    $http_authorization;

Can be used along with the fastcgi_cache_bypass directive.

Sets a parameter that should be passed to the FastCGI 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 fastcgi_param directives defined on the current level.

The following example shows the minimum required settings for PHP:

fastcgi_param SCRIPT_FILENAME /home/www/scripts/php$fastcgi_script_name;
fastcgi_param QUERY_STRING    $query_string;

The SCRIPT_FILENAME parameter is used in PHP for determining the script name, and the QUERY_STRING parameter is used to pass request parameters.

For scripts that process POST requests, the following three parameters are also required:

fastcgi_param REQUEST_METHOD  $request_method;
fastcgi_param CONTENT_TYPE    $content_type;
fastcgi_param CONTENT_LENGTH  $content_length;

If PHP was built with the --enable-force-cgi-redirect configuration parameter, the REDIRECT_STATUS parameter should also be passed with the value “200”:

fastcgi_param REDIRECT_STATUS 200;

If a directive is specified with if_not_empty (1.1.11) then such a parameter will not be passed to the server until its value is not empty:

fastcgi_param HTTPS           $https if_not_empty;

Sets an address of the FastCGI server. An address can be specified as a domain name or an address, and a port, for example,

fastcgi_pass localhost:9000;

or as a UNIX-domain socket path:

fastcgi_pass unix:/tmp/fastcgi.socket;

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.

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

fastcgi_read_timeout 60s;

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

fastcgi_send_timeout 60s;

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

Defines a regular expression that captures a value for the $fastcgi_path_info variable. A regular expression should have two captures, the first becomes a value of the $fastcgi_script_name variable, the second becomes a value of the $fastcgi_path_info variable. For example, with these settings

location ~ ^(.+\.php)(.*)$ {
    fastcgi_split_path_info       ^(.+\.php)(.*)$;
    fastcgi_param SCRIPT_FILENAME /path/to/php$fastcgi_script_name;
    fastcgi_param PATH_INFO       $fastcgi_path_info;

and the “/show.php/article/0001” request, the SCRIPT_FILENAME parameter will be equal to “/path/to/php/show.php”, and the PATH_INFO parameter will be equal to “/article/0001”.

fastcgi_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:

fastcgi_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 fastcgi_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;

    fastcgi_pass         backend:9000;
    ...

    fastcgi_store        on;
    fastcgi_store_access user:rw group:rw all:r;
    fastcgi_temp_path    /data/temp;

    alias                /data/www/;
}

fastcgi_store_access user:rw;

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

fastcgi_store_access user:rw group:rw all:r;

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

fastcgi_store_access group:rw all:r;

fastcgi_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 FastCGI server to temporary files is enabled. By default, size is limited by two buffers set by the fastcgi_buffer_size and fastcgi_buffers directives. The maximum size of a temporary file is set by the fastcgi_max_temp_file_size directive.

fastcgi_temp_path fastcgi_temp;

Defines a directory for storing temporary files with data received from FastCGI servers. Up to three-level subdirectory hierarchy can be used underneath the specified directory. For example, in the following configuration

fastcgi_temp_path /spool/nginx/fastcgi_temp 1 2;

a temporary file might look like this:

/spool/nginx/fastcgi_temp/7/45/00000123457

HTTP request header fields are passed to the FastCGI server as parameters. In applications and scripts running as FastCGI servers, these parameters are usually made available as environment variables. For example, the “User-Agent” header field is passed as the HTTP_USER_AGENT parameter. In addition to HTTP request header fields it is possible to pass arbitrary parameters using the fastcgi_param directive.

The ngx_http_fastcgi_module module supports embedded variables that can be used to set parameters using the fastcgi_param directive:

$fastcgi_script_name

request URI or, if a URI ends with a slash, request URI with an index file name configured by the fastcgi_index directive appended to it. This variable can be used to set the SCRIPT_FILENAME and PATH_TRANSLATED parameters that determine the script name in PHP. For example, for the “/info/” request with the following directives

fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME /home/www/scripts/php$fastcgi_script_name;

the SCRIPT_FILENAME parameter will be equal to “/home/www/scripts/php/info/index.php”.

When using the fastcgi_split_path_info directive, the $fastcgi_script_name variable equals to the value of the first capture set by the directive.

$fastcgi_path_info

the value of the second capture set by the fastcgi_split_path_info directive. This variable can be used to set the PATH_INFO parameter.