Apache Module mod_fcgid

Available Languages:  en 

Summary

Any program assigned to the handler fcgid-script is processed using the FastCGI protocol; mod_fcgid starts a sufficient number instances of the program to handle concurrent requests, and these programs remain running to handle further incoming requests. This is significantly faster than using the default mod_cgi or mod_cgid modules to launch the program upon each request. However, the programs invoked by mod_fcgid continue to consume resources, so the administrator must weigh the impact of invoking a particular program once per request against the resources required to leave a sufficient number of instances running continuously.

The pool of fcgid-invoked programs is shared between all httpd workers. Configuration directives below let the administrator tune the number of instances of the program that will run concurrently.

Specific executables are assigned this handler either by having a name containing an extension defined by the AddHandler directive, or with an override using the SetHandler directive (e.g., for all files in a specific directory such as cgi-bin).

Some changes have been made in the ASF release of mod_fcgid which can affect existing configurations. All documentation refers to new names for the directives. (The old names still work but are now deprecated.) Please read the Upgrade Notes for details.

For an introduction to using CGI scripts with Apache, see the generic tutorial on Dynamic Content with CGI.

mod_fcgid requires mod_unixd to be loaded before itself in the httpd config.

Upgrade Notes

The following changes have been made in the ASF release of mod_fcgid and should be considered when upgrading from the original version by Ryan Pan (Pan Qingfeng).

• All directives have been renamed in order to use a common prefix "Fcgid". Underscores in directive names have been eliminated in favor of CamelCase. The old directive names will still work but are deprecated. To fix your configuration you can use the sed script build/fixconf.sed. The following table contains old and new directive names:

  Old Name	New Name
  BusyScanInterval	FcgidBusyScanInterval
  BusyTimeout	FcgidBusyTimeout
  DefaultInitEnv	FcgidInitialEnv
  DefaultMaxClassProcessCount	FcgidMaxProcessesPerClass
  DefaultMinClassProcessCount	FcgidMinProcessesPerClass
  ErrorScanInterval	FcgidErrorScanInterval
  FastCgiAccessChecker	FcgidAccessChecker
  FastCgiAccessCheckerAuthoritative	FcgidAccessCheckerAuthoritative
  FastCgiAuthenticator	FcgidAuthenticator
  FastCgiAuthenticatorAuthoritative	FcgidAuthenticatorAuthoritative
  FastCgiAuthorizer	FcgidAuthorizer
  FastCgiAuthorizerAuthoritative	FcgidAuthorizerAuthoritative
  FCGIWrapper	FcgidWrapper
  IdleScanInterval	FcgidIdleScanInterval
  IdleTimeout	FcgidIdleTimeout
  IPCCommTimeout	FcgidIOTimeout
  IPCConnectTimeout	FcgidConnectTimeout
  MaxProcessCount	FcgidMaxProcesses
  MaxRequestInMem	FcgidMaxRequestInMem
  MaxRequestLen	FcgidMaxRequestLen
  MaxRequestsPerProcess	FcgidMaxRequestsPerProcess
  OutputBufferSize	FcgidOutputBufferSize
  PassHeader	FcgidPassHeader
  PHP_Fix_Pathinfo_Enable	FcgidFixPathinfo
  ProcessLifeTime	FcgidProcessLifeTime
  SharememPath	FcgidProcessTableFile
  SocketPath	FcgidIPCDir
  SpawnScore	FcgidSpawnScore
  SpawnScoreUpLimit	FcgidSpawnScoreUpLimit
  TerminationScore	FcgidTerminationScore
  TimeScore	FcgidTimeScore
  ZombieScanInterval	FcgidZombieScanInterval

Fcgid and Apache ErrorDocument

The core directive ErrorDocument allows the user to specify custom error pages for specific HTTP error codes. An important note must be made: if the error page is generated by the fastcgi script, mod_fcgid will pass the response down to the output filter chain bypassing the Apache's ErrorDocuments. Conversely, if the error is generated by Apache itself (for example, a HTTP 404 due to a missing resource) then the ErrorDocument set will be used. This behaviour is the most conservative one to interfere as little as possible with the fastcgi's response generation logic. mod_proxy shows the same behaviour but it offers ProxyErrorOverride to force the use of ErrorDocuments, meanwhile mod_fcgid does not. A common workaround is to instruct the fcgi script to generate the ErrorDocuments to have full control of the response content.

Examples

The first example is a very simple Perl FastCGI application, and its configuration directives. This is typical for FastCGI applications which require no special configuration.

PHP applications are usually configured using the FcgidWrapper directive and a corresponding wrapper script. The wrapper script can be an appropriate place to define any environment variables required by the application, such as PHP_FCGI_MAX_REQUESTS or anything else. (Environment variables can also be set with FcgidInitialEnv, but they then apply to all applications.)

Here is an example that uses a wrapper script to invoke PHP:

Process Management

mod_fcgid has several types of controls which affect the creation of additional application processes:

mod_fcgid has several types of controls which affect the termination of existing application processes:

Several of the directives control processing for a process class. A process class is the set of processes which were started with the same executable file and share certain other characteristics such as virtual host and identity. Two commands which are links to or otherwise refer to the same executable file share the same process class.

Information about each process will be displayed in the mod_status server-status page.

FcgidAccessChecker Directive

Access checking or, more formally, access control, is a procedure which verifies that the client is allowed to access a resource, using some mechanism other than authentication and authorization.

Key environment variables passed to the application for access checking are:

FCGI_APACHE_ROLE

set to ACCESS_CHECKER; by checking the current role, the same FastCGI application can handle multiple stages of request processing

The application must output a Status line to indicate the result of the check.

Directive

This directive controls whether or not other access checkers are allowed to run when this module has an access checker configured and it fails a request. If this directive is On (default) and a FastCGI access checker returns a failure status, a failure is returned to the client without giving other access checkers a chance to allow access. If this directive is Off, other access checkers will be called.

FcgidAuthenticator Directive

Authentication is the procedure which verifies that the user is who they claim they are. This directive specifies the full path to a FastCGI application which will handle authentication for a particular context, such as a directory.

Key environment variables passed to the application on authentication are:

REMOTE_USER

set to the user id of the client

REMOTE_PASSWD

set to the plain text password provided by the client

FCGI_APACHE_ROLE

set to AUTHENTICATOR; by checking the current role, the same FastCGI application can handle multiple stages of request processing

The application must output a Status line to indicate the result of authentication.

FcgidAuthenticatorAuthoritative Directive

This directive controls whether or not other authenticators are allowed to run when this module has an authenticator configured and it fails a request. If this directive is On (default) and a FastCGI authenticator returns a failure status, a failure is returned to the client without giving other authenticators a chance to validate the client identity. If this directive is Off, other authenticators will be called.

FcgidAuthorizer Directive

Authorization is the procedure which verifies that the user is allowed to access a particular resource. This directive specifies the full path to a FastCGI application which will handle authorization for a particular context, such as a directory.

Key environment variables passed to the application on authorization are:

REMOTE_USER

set to the user id of the client, which has already been authenticated

FCGI_APACHE_ROLE

set to AUTHORIZER; by checking the current role, the same FastCGI application can handle multiple stages of request processing

The application must output a Status line to indicate the result of authorization.

FcgidAuthorizerAuthoritative Directive

This directive controls whether or not other authorizers are allowed to run when this module has an authorizer configured and it fails a request. If this directive is On (default) and a FastCGI authorizer returns a failure status, a failure is returned to the client without giving other authorizer a chance to access the resource. If this directive is Off, other authorizers will be called.

FcgidBusyScanInterval Directive

The module performs the FcgidBusyTimeout check at this interval.

FcgidBusyTimeout Directive

This is the maximum time limit for request handling. If a FastCGI request does not complete within FcgidBusyTimeout seconds, it will be subject to termination. Because the check is performed at the interval defined by FcgidBusyScanInterval, request handling may be allowed to proceed for a longer period of time.

The purpose of this directive is to terminate hung applications. The default timeout may need to be increased for applications that can take longer to process the request.

FcgidCmdOptions Directive

This directive allows processing options to be specified for a specific command spawned by mod_fcgid. Each option for the command corresponds to another directive that normally applies to all commands started within a particular context. If a particular option is not specified on this directive, the default will be used.

The following table provides a list of options and corresponding directives:

Multiple environment variables are defined by repeating the InitialEnv option.

When /usr/local/bin/wrapper is spawned, its initial environment contains the MAX_REQUESTS=2000 environment variable setting; additionally, mod_fcgid will terminate it after it has handled 2000 requests, and I/O operations will time out after 90 seconds. Directives corresponding to other options, such as FcgidIdleTimeout or FcgidProcessLifeTime, will be ignored for this command; defaults will be used for options not specified on FcgidCmdOptions.

FcgidConnectTimeout Directive

This is the maximum period of time the module will wait while trying to connect to a FastCGI application on Windows. (This directive is not respected on Unix, where AF_UNIX defaults will apply.)

This setting will apply to all applications spawned for this server or virtual host. Use FcgidCmdOptions to apply this setting to a single application.

FcgidErrorScanInterval Directive

This is the interval at which the module will handle pending process termination. Termination is pending for any processes which have exceeded FcgidIdleTimeout or FcgidProcessLifeTime.

Unix: mod_fcgid will terminate such processes with SIGTERM; if the process is still active during the next scan, the process will be terminated with SIGKILL. Thus, this directive controls the amount of time for orderly process terminate before being forcibly killed.

FcgidFixPathinfo Directive

This directive enables special SCRIPT_NAME processing which allows PHP to provide additional path information. The setting of FcgidFixPathinfo should mirror the cgi.fix_pathinfo setting in php.ini.

FcgidIdleScanInterval Directive

This is the interval at which the module will search for processes which have exceeded FcgidIdleTimeout or FcgidProcessLifeTime.

FcgidIdleTimeout Directive

Application processes which have not handled a request for this period of time will be terminated, if the number of processses for the class exceeds FcgidMinProcessesPerClass. A value of 0 disables the check.

This idle timeout check is performed at the frequency of the configured FcgidIdleScanInterval.

This setting will apply to all applications spawned for this server or virtual host. Use FcgidCmdOptions to apply this setting to a single application.

FcgidInitialEnv Directive

Use FcgidInitialEnv to define environment variables to pass to the FastCGI application. This directive can be used multiple times.

This setting will apply to all applications spawned for this server or virtual host. Use FcgidCmdOptions to apply this setting to a single application.

FcgidIOTimeout Directive

This is the maximum period of time the module will wait while trying to read from or write to a FastCGI application.

This setting will apply to all applications spawned for this server or virtual host. Use FcgidCmdOptions to apply this setting to a single application.

FcgidIPCDir Directive

This module uses AF_UNIX sockets or named pipes, depending on the platform, to communicate with FastCGI applications. This directive specifies the directory where those sockets or named pipes will be created.

FcgidMaxProcesses Directive

This directive sets the maximum number of FastCGI application processes which can be active at one time.

FcgidMaxProcessesPerClass Directive

This directive sets the maximum number of processes that can be started for each process class.

This setting will apply to all applications spawned for this server or virtual host. Use FcgidCmdOptions to apply this setting to a single application.

FcgidMaxRequestInMem Directive

This module reads the entire request body from the client before sending it to the application. Normally the request body will be stored in memory. Once the amount of request body read from the client exceeds FcgidMaxRequestInMem bytes, the remainder of the request body will be stored in a temporary file.

FcgidMaxRequestLen Directive

If the size of the request body exceeds this amount, the request will fail with 500 Server Error.

Administrators should change this to an appropriate value for their site based on application requirements.

See also

• FcgidMaxRequestInMem

FcgidMaxRequestsPerProcess Directive

FastCGI application processes will be terminated after handling the specified number of requests. A value of 0 disables the check.

Certain applications, notably PHP as FastCGI, have their own facility for terminating after handling a certain number of requests. This directive can be used to avoid sending additional requests to the application after it has handled its limit.

This setting will apply to all applications spawned for this server or virtual host. Use FcgidCmdOptions to apply this setting to a single application.

FcgidMinProcessesPerClass Directive

This directive sets the minimum number of processes that will be retained in a process class after finishing requests.

This setting will apply to all applications spawned for this server or virtual host. Use FcgidCmdOptions to apply this setting to a single application.

FcgidOutputBufferSize Directive

This is the maximum amount of response data the module will read from the FastCGI application before flushing the data to the client.

FcgidPassHeader Directive

This directive specifies the name of a request header which will be passed to the FastCGI application as an environment variable. The name of the environment variable is derived from the value specified on this directive, as discussed below:

The legacy behavior is to use the value specified on this directive as the environment variable name, converting hyphens to underscores. No case conversion is performed.

Beginning with release 2.3.6, an additional environment variable is created. The value specified on this directive is converted to upper case, prefixed with HTTP_, and hyphens are converted to underscores.

FcgidProcessLifeTime Directive

Idle application processes which have existed for greater than this time will be terminated, if the number of processses for the class exceeds FcgidMinProcessesPerClass. A value of 0 disables the check.

This process lifetime check is performed at the frequency of the configured FcgidIdleScanInterval.

This setting will apply to all applications spawned for this server or virtual host. Use FcgidCmdOptions to apply this setting to a single application.

FcgidProcessTableFile Directive

This module uses shared memory on Unix to maintain state which is shared between httpd processes. This directive specifies the name of the shared memory file.

FcgidSpawnScore Directive

Lower values of this directive increase the allowed spawn rate.

Refer to the FcgidSpawnScoreUpLimit directive for more information.

FcgidSpawnScoreUpLimit Directive

A process activity score is maintained for each FastCGI application; the score is used to control the rate of spawning in order to avoid placing too much load on the system, particularly for applications that are repeatedly exiting abnormally.

The value of FcgidSpawnScore is added to the score for every spawned application process. The value of FcgidTerminationScore is added to the score for every terminated application process. The value of FcgidTimeScore is subtracted from the score every second.

When the current score is higher than the value of FcgidSpawnScoreUpLimit, no additional application processes will be spawned; subsequent requests must wait until an existing process is free or until the score decreases below the limit.

If the limit is reached under normal load, it may not be sufficient to simply increase the limit, as that would only delay the amount of time before the limit is reached again. Decrease the value of FcgidSpawnScore and/or FcgidTerminationScore, or increase the value of FcgidTimeScore, to allow a higher rate of spawning.

FcgidTerminationScore Directive

Lower values of this directive increase the allowed spawn rate. Negative values can be useful in some circumstances, such as allowing process replacement without increasing the score.

Refer to the FcgidSpawnScoreUpLimit directive for more information.

FcgidTimeScore Directive

Higher values of this directive increase the allowed spawn rate.

Refer to the FcgidSpawnScoreUpLimit directive for more information.

FcgidWin32PreventOrphans Directive

Uses Job Control Objects on Windows, only, to enforce shutdown of all fcgi processes created by the httpd worker when the httpd worker has been terminated. Processes terminated in this way do not have the opportunity to clean up gracefully, complete pending disk writes, or similar closure transactions, therefore this behavior is experimental and disabled, by default.

FcgidWrapper Directive

The given command is used to spawn FCGI server processes. If this directive is not used, the file pointed to by the request URL will be used instead. Options for the command can be included using quotation marks surrounding the command and options.

The optional suffix argument restricts the use of this FCGI server to all URLs with the given exact path suffix. A suffix needs to start with '.'.

The virtual flag signals that there will be no check whether the request URL actually points to an existing file. The only file which needs to exist is the wrapper itself.

The directive can be used multiple times. A wrapper defined without a suffix is used as a default in case no suffix matches.

FcgidZombieScanInterval Directive

The module checks for exited FastCGI applications at this interval. During this period of time, the application may exist in the process table as a zombie (on Unix).