Apache FastCGI

Apache has multiple implementations of the CGI and FastCGI specifications. The below are the most common and easiest to use.

See here for details on the specifications.

Mod_fcgid

mod_fcgid was designed to be a comprehensive upgrade from mod_cgi and mod_cgid.

Load the mod_fcgid module to enable it.

Perl Example

Consider the following Perl script, which should live under /var/www/fcgi-bin:

use CGI::Fast;

while (my $q = CGI::Fast->new) {
  print("Content-Type: text/plain\n\n");
  foreach $var (sort(keys(%ENV))) {
    $val = $ENV{$var};
    $val =~ s|\n|\\n|g;
    $val =~ s|"|\\"|g;
    print "${var}=\"${val}\"\n";
  }
}

With mod_fcgi, Apache can be made to execute this with very little configuration.

<Directory /var/www/fcgi-bin/>
  SetHandler fcgid-script
  Options +ExecCGI

  Order allow,deny
  Allow from all
</Directory>

PHP Example

PHP works very similarly. Consider the following script:

<?php
  phpinfo();
?>

Because many servers of significance are written in PHP, it's not realistic to require that they be installed under the web root. While the above script could live anywhere, the below configurations will reference /usr/local/myapp/ as its location.

A wrapper script under /var/www/fcgi-bin will be necessary. It should look like:

# PHP FastCGI processes exit after 500 requests by default.
PHP_FCGI_MAX_REQUESTS=10000
export PHP_FCGI_MAX_REQUESTS

# Replace with the path to your FastCGI-enabled PHP executable
exec /usr/local/bin/php-cgi

Finally, the Apache configuration should look like:

Alias /myapp/ /usr/local/myapp/
<Location /myapp/>
  AddHandler fcgid-script .php
  Options +ExecCGI
  FcgidWrapper /var/www/fcgi-bin/php-wrapper .php

  Order allow,deny
  Allow from all
</Location>

PHP-FPM

PHP-FPM is a more performant option, but requires the installation and configuration of a separate server. See here for details on doing that.

Load the mod_proxy and mod_proxy_fcgi modules to enable Apache to proxy to that server.

Apache just needs to be configured to proxy requests.

ProxyPass "/myapp/" "fcgi://localhost:9000/" enablereuse=on

The ProxyPassMatch directive will not only match multiple locations, but will implicitly append the requested URL to the second argument.

ProxyPassMatch "^/myapp/.*\.php(/.*)?$" "fcgi://localhost:9000/var/www/" enablereuse=on

Unix Sockets

If using a Unix socket to pass requests, the configuration should look like:

ProxyPassMatch "^/myapp/(.*\.php(/.*)?)$" "unix:/var/run/php-fpm.sock|fcgi://localhost/var/www/"

Note that the hostname and optional port following fcgi:// are ignored. (The document root is not ignored.)

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