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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

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

Foswiki bin URL
Foswiki root
 

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

Generic CPAN references as well as the most popular distribution packages are listed below

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.

It is difficult to recommend one or the other. In some cases one will work and the other will not. Most positive reports have been with mod_fcgidbut both have been tested and work with standard out-of-the-box Apache and Foswiki setups. mod_fcgid is easier to find as package because of its GPL license so it may be the best place to start. Fedora has mod_fcgid on the installation DVD now.

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

mod_fastcgi resources

Apache Configuration

ALERT! It is strongly recommended that users work from Foswiki:Support.ApacheConfigGenerator to create initial Apache configurations. This config generator is comprehensive and well tested; the examples below may be inadequate for your needs.

Using only .htaccess

Using only .htaccess file it's not possible to control the number of FastCGI processes, nor the user it'll be run with. We assume the webserver is configured to recognize files with .fcgi extension to be FastCGI scripts. We also need mod_rewrite or mod_actions enabled.

Examples
Notes:

IDEA! Directory paths are relative to Foswiki root.

IDEA! Usage of mod_fcgid is assumed. If you're using mod_fastcgi, replace fcgid-script with fastcgi-script.

ALERT! mod_fcgid is preffered over mod_fastcgi. The latter project receives very few updates and has some known issues, such as Foswiki:Support.Faq18, whereas mod_fcgid is a default module that is shipped with Apache httpd.

Using mod_rewrite:
# bin/.htaccess file

Options +ExecCGI

RewriteEngine On

# configure script is a special case, it must run as a CGI script:
RewriteCond %{REQUEST_URI} !/configure 

# avoid loops:
RewriteCond %{REQUEST_URI} !/foswiki.fcgi

RewriteRule ^(.*) /foswiki/bin/foswiki.fcgi/$1

<Files configure>
    SetHandler cgi-script
</Files>

Using mod_actions:
# bin/.htaccess file

Options +ExecCGI

Action foswiki-fcgid /foswiki/bin/foswiki.fcgi
SetHandler foswiki-fcgid

<Files configure>
    SetHandler cgi-script
</Files>

<Files foswiki.fcgi>
   SetHandler fcgid-script
</Files>

Using apache .conf

Direct access to Apache configuration files open more possibilities than with .htaccess, such as:
  • Configurable number of FastCGI processes
  • With mod_fastcgi:
    • Use remote FastCGI processes to service requests
      • This might be possible under mod_fcgid using a custom wrapper script with the FcgidWrapper directive and the virtual flag
    • Control the user the FastCGI processes run under

Using mod_fastcgi

ALERT! Consider using the newer and better-maintained mod_fcgid which is shipped standard with Apache httpd.

We can use static or dynamic servers: static servers are initialized with Apache itself and exists as long Apache is running. Dynamic servers are loaded on demand and killed if the aren't needed anymore.

See mod_fastcgi documentation for more options.

# Simple and traditional example.
Alias /foswiki/bin/configure /var/www/foswiki/bin/configure
Alias /foswiki/bin   /var/www/foswiki/bin/foswiki.fcgi

# Commenting the next line makes foswiki to be a dynamic server, loaded on demand
FastCgiServer /var/www/foswiki/bin/foswiki.fcgi -processes 3

<Directory /var/www/foswiki/bin>
   Options +ExecCGI
    <Files configure>
        SetHandler cgi-script
    </Files>
    <Files foswiki.fcgi>
        SetHandler fastcgi-script
    </Files>
</Directory>

Refer to tuning section below for a little discussion about the number of FastCGI processes.

# External server: could be running at another machine and/or a different user from the webserver

Alias /foswiki/bin/configure /var/www/foswiki/bin/configure
Alias /foswiki/bin   /var/www/foswiki/bin/foswiki.fcgi

# Running an external server on the same machine:
FastCgiExternalServer /var/www/foswiki/bin/foswiki.fcgi -socket /path/to/foswiki.sock

# Or at another machine:
FastCgiExternalServer /var/www/foswiki/bin/foswiki.fcgi -host example.com:8080

<Directory /var/www/foswiki/bin>
    Options +ExecCGI
    <Files configure>
        SetHandler cgi-script
    </Files>
    <Files foswiki.fcgi>
        SetHandler fastcgi-script
    </Files>
</Directory>

When you're using external servers you must run the FastCGI processes manually:
$ cd /var/www/foswiki/bin
# To start a pool of processes, listening to a local UNIX socket:
$ ./foswiki.fcgi --listen /path/to/foswiki.sock --nproc 3 --pidfile /path/to/pidfile.pid --daemon
# Or listening to a local :port address:
$ ./foswiki.fcgi --listen :port --nproc 3 --pidfile /path/to/pidfile.pid --daemon

Run ./foswiki.fcgi --help for details on the options.

Using mod_fcgid
Comparison to mod_fastcgi:
  • Compatible API from Foswiki's point of view, drop-in replacement
  • Maintained as a part of the standard Apache httpd distribution
  • Does not itself provide a mechanism to run the FastCGI processes as a different user (possible through other means)
  • mod_fcgid documentation suggests that only dynamic servers are supported
  • No (easy) way to use FastCGI processes running on another machine; but it might be possible with a custom wrapper script and the FcgidWrapper directive with the virtual flag

# Simple and traditional example.
Alias /foswiki/bin/configure /var/www/foswiki/bin/configure
Alias /foswiki/bin   /var/www/foswiki/bin/foswiki.fcgi

<Directory /var/www/foswiki/bin>
   Options +ExecCGI
    <Files configure>
        SetHandler cgi-script
    </Files>
    <Files foswiki.fcgi>
        SetHandler fcgid-script
    </Files>
</Directory>

ApacheLogin

If you use ApacheLogin instead of TemplateLogin you'll need to add something like the following directives:

<LocationMatch "^/+foswiki/+bin/+(attach|edit|manage|rename|save|upload|.*auth|rest|login|logon)">
   AuthType Basic
   AuthName "Foswiki login realm"
   AuthUserFile "/var/www/foswiki/data/.htpasswd"
   Require valid-user
</LocationMatch>

Lighttpd

You need to load both mod_cgi and mod_fastcgi. The first is used to run configure script. From what I understood from the documentation, lighttpd doesn't support dynamic servers.

# Example with FastCGI processes launched by the webserver
$HTTP["url"] =~ "^/foswiki/bin/configure" {
    alias.url += ( "/foswiki/bin" => "/var/www/foswiki/bin" )
    cgi.assign = ( "" => "" )
}

$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/configure" {
    alias.url += ( "/foswiki/bin" => "/var/www/foswiki/bin" )
    cgi.assign = ( "" => "" )
}

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

Tuning

Except from Apache 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.

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

FastCGI specification defines an authorizer role besides the common used responder. Foswiki, by default, doesn't check access to attachments, unless you use viewfile script. The problem with that script is that it's slow and resource-hungry. In future releases, this contrib will provide a way to add access checks to attachments with very little overhead, using the authorizer role.

ALERT! This is a persistent engine, so you need to restart the web server after some configuration update is performed. However, there is an auto-reload mechanism that apply changes without a web server restart. Unfortunately, there is a delay: 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.

ALERT! All examples above have an exception to configure script. This script needs to run as a plain CGI script. There are some legacy extensions (not updated to Foswiki:Development/FoswikiStandAlone design) that adds scripts to the bin/ directory. You need to add exceptions for these scripts as well.

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

Info

Author(s) Gilmar Santos Jr
Copyright © 2008 Gilmar Santos Jr and Foswiki Contributors
License: GPL (Gnu General Public License)
Release: 0.9.5
Version: 12487 (2011-09-08)
Change History:  
08 Sep 2011 (0.9.5) Foswikitask:Item9957 - remove uninitialised value log message
26 Oct 2010 (0.9.4) Foswikitask:Item9902 - Adding more resources about how to get and install CPAN lib and mod_fcgid or mod_fastcgi. Also includes temporary fix from Foswikitask:Item1515: added maxRequests to ease memory leaks and fix for Foswikitask:Item9456: Taint error with foswiki.fcgi
17 Sep 2010 (0.9.3) Foswikitask:Item9701 - Documentation update, suggest mod_fcgid preferred over mod_fastcgi
03 Sep 2010 Foswikitask:Item9456 - Taint error, Foswikitask:Item9390 - LocalSite.cfg error handling, Foswikitask:Item8765 - Perl coding issue, Foswikitask:Item1315 - Support information
21 Dec 2009 Foswiki:Main.ItaloValcy: fix Foswikitask:Item8238
24 Jan 2009 Documentation enhancements and some fixes (Foswikitask:Item853)
25 Dec 2008 Initial Release
Dependencies:
NameVersionDescription
FCGI >0.67FastCGI perl library
File::Spec >0This module is shipped as part of standard perl
Cwd >0This module is shipped as part of standard perl
POSIX >0This module is shipped as part of standard perl
Getopt::Long >2.37Extended processing of command line options
Pod::Usage >1.35print a usage message from embedded pod documentation
Home page: http://foswiki.org/Extensions/FastCGIEngineContrib
Support: http://foswiki.org/Support/FastCGIEngineContrib
Topic revision: r1 - 08 Sep 2011, UnknownUser
 
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