FastCGI Engine Contrib

Permits Foswiki to be executed with FastCGI

Overview

FastCGI is a technology to deliver dynamic web content. It differs from CGI cause it remains persistent between requests, instead of CGI approach of a new forked process per request. This way there is a significant performance improvement, since all overhead related to create a new process, load the interpreter and compile the code is skipped.

Some FastCGI features:

• The number of persistent processes is configurable, independent of the web server. This leads to easier capacity planning/management.
• Processes can be run with a different user: more security.
• Processes can be run on another machines: easier load balancing.

Installation Instructions

We recommend that you use the thoroughly tested Foswiki:Support.ApacheConfigGenerator for creating your apache configuration. It can generate a comprehensive Apache configuration for your installation.

This section is about how to configure FastCGIEngineContrib, considering many possible environments:

• Apache web server
  • Using only .htaccess (typically on host services)
  • With access to apache configuration files
    • Remote FastCGI processes
  • Using mod_fcgid or mod_fastcgi
• Lighttpd web server
  • Remote FastCGI processes
• nginx web server
  • remote FastCGI processes

Installation of the FCGI CPAN library

FastCGIEngineContrib uses a CPAN library called FCGI which is not normally distributed with Perl. Version of FCGI should be 0.67 or later. See SystemRequirements (Foswiki:System.SystemRequirements) for a detailed requiremments by server distribution.

• Debian / Ubuntu: apt-get install libfcgi-perl
• RedHat / Centos: yum install perl-FCGI
• SuSE: zypper install  perl-FCGI
• Gentoo: emerge dev-perl/FCGI
• FreeBSD: pkg install p5-FCGI
• CPAN: cpanm FCGI

Apache

Apache Module

There are two options that basicly do the same thing

• mod_fastcgi which is the oldest implementation. It is released under a custom non-free license but it is free of charge.
• mod_fcgid which is the newer implementation released under the GPL license and now part of the Apache Foundation.

mod_fcgid is provided by default with apache2, and is recommended for simplicity of installation and configuration.

Below are some resources for the most common Linux distributions. The actual versions of the latest packages may have changed since this documentation was written.

mod_fcgid resources

• Sources - http://httpd.apache.org/mod_fcgid/
• Debian - http://packages.debian.org/search?searchon=names&keywords=libapache2-mod-fcgid

Apache Configuration

It is strongly recommended that users work from Foswiki:Support.ApacheConfigGenerator to create initial Apache configurations. This config generator is comprehensive and well tested.

There is one important parameter which should be consistent with the largest ATTACHFILESIZELIMIT of any web. FcgidMaxRequestLen must be large enough to permit upload of the largest possible attachment, or the upload will fail with a 500 status. Be sure the FcgidMaxRequestLen is larger so that the user will get a friendly error message from Foswiki. The default limit on recent Apache releases is 131072 bytes. It is not possible to override this in a .htaccess file.

Foswiki also ships with an example apache configuration, and example .htaccess files which include Fcgi example configurations.

Lighttpd

You need to load mod_fastcgi.

# Example with FastCGI processes launched by the webserver

$HTTP["url"] =~ "^/foswiki/bin/" {
    alias.url += ( "/foswiki/bin" => "/var/www/foswiki/bin/foswiki.fcgi" )
    fastcgi.server = ( ".fcgi" => (
            (
                "socket"    => "/var/www/foswiki/working/tmp/foswiki.sock",
                "bin-path"  => "/var/www/foswiki/bin/foswiki.fcgi",
                "max-procs" => 3
            ),
        )
    )
}

# Example with external FastCGI processes (running on the same host, with another user or at a remote machine)

$HTTP["url"] =~ "^/foswiki/bin/" {
    alias.url += ( "/foswiki/bin" => "/var/www/foswiki/bin/foswiki.fcgi" )
    fastcgi.server = ( ".fcgi" => (
            (
                "host"    => "example.com",
                "port"    => "8080",
            ),
        )
    )
}

Nginx

In contrast to Apache or Lighttpd, Nginx does not control the life time of the foswiki.fcgi backend process. Instead you will have to start it yourself using the system's init process. The FCGI::ProcManager class will then take care of (re-)spawning enough child processes as required.

Configure nginx to contact a foswiki.fcgi process on some socket on the localhost:

server {
    listen       80;
    server_name  nginx.domain.com;

    set $foswiki_root "/var/www/foswiki";
    root $foswiki_root;

    access_log  /var/log/nginx/foswiki-access.log;
    error_log   /var/log/nginx/foswiki-error.log;
    #error_log   /var/log/nginx/foswiki-error.log debug;

    client_max_body_size 10M;   # Set to maximum attachment size, See also ATTACHFILESIZELIMIT

    location = / {
        root $foswiki_root;
    rewrite .* /Main/WebHome;
    }

    location ~ (^/pub) {
        allow all;
    }

    location ~ ^/bin/ {
           gzip off;
           #fastcgi_pass             unix:/var/run/nginx/foswiki.sock;
           fastcgi_pass             127.0.0.1:9000;
           fastcgi_split_path_info  ^(/bin/\w+)(.*);
           #  Captures two variables   ($fastcgi_script_name) and ($fastcgi_path_info)
           fastcgi_param            SCRIPT_FILENAME $foswiki_root/bin/$fastcgi_script_name;
           fastcgi_param            SCRIPT_NAME     $fastcgi_script_name;
           fastcgi_param            PATH_INFO       $fastcgi_path_info;
           include fastcgi_params;
       }

    location ~ (^/lib|^/data|^/locale|^/templates|^/tools|^/work) {
        deny all;
    }

    if ($http_user_agent ~
^SiteSucker|^iGetter|^larbin|^LeechGet|^RealDownload|^Teleport|^Webwhacker|^WebDevil|^Webzip|^Attache|^SiteSnagger|^WX_mail|^EmailCollector|^WhoWhere|^Roverbot|^ActiveAgent|^EmailSiphon|^CrownPeak-HttpAgent|^$) {
        rewrite .* /404.html break;
   }

    location ~ ^/(.*)$ {
        rewrite ^/(.*)$ /bin/view/$1;
    }
}

Add the foswiki.fcgi process into the system init.

Integrate the foswiki.fgi process into the system's init process use the two helper scripts in the tools directory:

• Conventional init scripts (Should also work with systemd)
  • tools/foswiki.init-script: copy this to /etc/init.d/foswiki; make the file executable using chmod +x /etc/init.d/foswiki, and ensure that it is assigned to user/group root.
  • tools/foswiki.defaults: copy this to /etc/default/foswiki and make appropriate adjustments;
    • make sure the process uses the same socket as configured in nginx (see above, defaults to 127.0.0.1:9000)
    • verify that the FOSWIKI_ROOT setting points to your foswiki installation.

• systemd specific service files (Used in place of the init scripts. Don't use both!)
  • tools/systemd/foswiki-fastcgi.service: copy this to /etc/systemd/system/foswiki.service.

• FreeBSD init scripts
  • tools/foswiki.freebsd.init-script:
  • tools/foswiki.freebsd.etc-defaults:

Note: The service file does not honor all of the variables in tools/foswiki.defaults. If you need to override any of:

• The user/group - defaults to www-data
• The PIDFile - defaults to /var/www/foswiki/working/foswiki.pid
• The scripts directory - defaults to /var/www/foswiki/bin/

Then the /etc/systemd/system/foswiki.service file must be edited directly, or overridden by a systemd "drop-in" file created in /etc/systemd/system/foswiki.d/foswiki.conf.

If your system uses systemd, then you will need to trigger a re-read of the init scripts and service files by running (as root): systemctl daemon-reload. This must be done any time the init scripts or service files are modified.

You should now be able to control the backend processes using either:

• service foswiki start/stop/reload/restart/status. or
• /etc/init.d/foswiki start/stop/reload/restart/status

Finally, add the service to the runlevels using update-rc.d foswiki defaults to make sure the service is started on system startup time.

Customizing the fcgi process

• Changing the name of the process / init script
  • Copy /etc/init.d/foswiki, /etc/defaults/foswiki and if used, /etc/systemd/system/foswiki.service, to a new name (ex. myfoswiki)
  • Edit the init script to use the new name internally. (The foswiki.service file would need similar changes not detailed here.)

    # Provides:          myfoswiki
    # Short-Description: Start the myfoswiki backend server.
    NAME=myfoswiki                <== Should match script name
    # The following defaults are overridden in etc/default/foswiki
    FOSWIKI_PNAME=myfoswiki       <== Process name displayed in =ps aux=
    

  • Make sure the new instance is using a unique fastcgi_pass and matching FOSWIKI_BIND

Tuning

Except from Apache configured using only .htaccess file, it's possible to adjust the number of FastCGI processes. There is no magic number: it depends on some variables, like the hardware resources and access load. If you set this number too low, users may experience high latencies and you'll not use all hardware potential, on the other hand if this setting is adjusted too high then the server can be forced to use swap, what degrades performance a lot.

Due to possible memory growth, it's recommended to automatically restart the FCGI handlers afer they serve some number of requests. On Apache, this is done using the FcgidMaxRequestsPerProcess 500 setting. On other web servers, use the Foswiki configuration setting: {FastCGIContrib}{MaxRequests} = 100

Dynamic servers are more useful when Foswiki access load on the server is low and/or it's used for something in addition to Foswiki. Under high loads, static servers can deliver better performance.

Known Issues

This is a persistent engine, so you need to restart the web server after any configuration changes. The Foswiki FastCGI implementation on Apache has an auto-reload mechanism that can detect and restart the handlers when the LocalSite.cfg is changed. However there is a delay, and it is recommended to restart apache. After the update, each process will still serve one more request before reloading itself (e.g. if you're using 3 processes, the next 3 requests after the update will not be affected. The update will take effect on the requests made after the initial 3). This reloading mechanism works only on operating systems that have the exec(2) system call, like Linux and other POSIX compliant systems.

FastCGI support on IIS 6.0 (and maybe other versions) is broken with respect to the STDERR stream. This may cause problems.

Dependencies

Change History