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
- Using
mod_fcgid or mod_fastcgi
- Lighttpd web server
- nginx web server
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
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
Directory paths are relative to Foswiki root.
Usage of
mod_fcgid is assumed. If you're using
mod_fastcgi, replace
fcgid-script with
fastcgi-script.
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
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",
),
)
)
}
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.
First, let's configure nginx to contact a
foswiki.fcgi process on some socket on the localhost:
server {
...
root /var/www/foswiki;
location = / {
try_files $uri @foswiki;
}
location ~ ^/(?:/foswiki/bin/)?([A-Z_].*)$ {
rewrite ^/(.*)$ /foswiki/bin/view/$1;
}
location ~ ^/pub/(System|Applications|images|cache)/ {
expires 8h;
gzip_static on;
}
location /pub {
rewrite ^/pub/(.*)$ /foswiki/bin/viewfile/$1;
}
location /foswiki/bin {
try_files $uri @foswiki;
}
location @foswiki {
gzip off;
fastcgi_pass 127.0.0.1:9000;
fastcgi_split_path_info ^/foswiki/bin/(.+?)(/.*)$;
fastcgi_param SCRIPT_FILENAME /var/www/foswiki/bin/foswiki.fcgi;
fastcgi_param PATH_INFO $fastcgi_path_info;
include fastcgi_params;
}
location ~ (^/lib|^/data|^/locale|^/templates|^/tools|^/work) {
deny all;
}
...
}
Next, to integrate the
foswiki.fgi process into the system's init process use the two helper scripts in the
tools directory:
-
foswiki.init-script: copy this to /etc/init.d/foswiki; make the file executable using chmod +x /etc/init.d/foswiki
-
foswiki.defaults: copy this to /etc/defaults/foswiki and make appropriate adjustmenst; make sure the process uses the same socket as configured in nginx (see above, defaults to 127.0.0.1:9000)
You should now be able to control the backend processes using
service 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.
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.
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.
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.
FastCGI support on IIS 6.0 (and maybe other versions) is
broken with respect to the
STDERR stream. This may cause problems.
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