Proxying to FastCGI in Ubuntu/Apache 2.4

Ubuntu 12.04

In Apache under Ubuntu 12.04 LTS, to pass a request off to a FastCGI process (such as PHP-FPM), I usually installed libapache2-mod-fastcgi. It looked something like this:

$ sudo add-apt-repository -y ppa:ondrej/apache2
$ sudo apt-key update
$ sudo apt-get update
$ sudo apt-get install -y apache2 apache2-mpm-event libapache2-mod-fastcgi

This was nice as it would allow the use of one configuration file for handling all FastCGI requests. For example, to hand off requests to PHP-FPM.
I'd create /etc/apache2/conf-available/php5-fpm.conf:

<IfModule mod_fastcgi.c>
        AddHandler php5-fcgi .php
        Action php5-fcgi /php5-fcgi
        Alias /php5-fcgi /usr/lib/cgi-bin/php5-fcgi
        FastCgiExternalServer /usr/lib/cgi-bin/php5-fcgi -socket /var/run/php5-fpm.sock -pass-header Authorization
        <Directory /usr/lib/cgi-bin>
                Options ExecCGI FollowSymLinks
                SetHandler fastcgi-script
                Require all granted
        </Directory>
</IfModule>

Once this was enabled (via a symlink to /etc/apache2/conf-enabled/php5-fpm.conf), PHP requests would be handed off to the PHP-FPM process listening on the unix socket /var/run/php5-fpm.sock.

Ubuntu 14.04

In Ubuntu 14.04, the libapache2-mod-fastcgi module isn't available by default (nor with the ondrej/apache2 repository). This is because it's part of the "Multiverse" repositories, which are not available by default.
We can still get that module, however. To do so, edit /etc/apt/sources.list and add the following repositories:

deb http://archive.ubuntu.com/ubuntu trusty multiverse
deb http://archive.ubuntu.com/ubuntu trusty-updates multiverse
deb http://security.ubuntu.com/ubuntu trusty-security multiverse

Then you can run sudo apt-get update && sudo apt-get install libapache2-mod-fastcgi to install and use those modules, just like we did in Ubuntu 12.04.

"Simpler" Method:

Instead of going through those hoops, however, let's use what Apache2 does come with in Ubuntu 14.04: mod_proxy and mod_proxy_fcgi. Working together, these modules can accomplish the same as the third-party libapache2-mod-fastcgi.
Overall, this comes with a simpler configuration and a very similar configuration can be used for passing requests off to HHVM and even non-PHP applications.
Here's what the process of using those modules looks like:

Install PHP-FPM

This example will use PHP-FPM as the fastCGI process. Let's install that:

$ sudo apt-get install php5-fpm

Our setup will now need PHP5-FPM to listen over a TCP socket instead of a unix socket. This means changing some configuration - this one-liner will do the trick:

$ sudo sed -i "s/listen =.*/listen = 127.0.0.1:9000/" /etc/php5/fpm/pool.d/www.conf

Instead of having PHP-FPM listen on the unix socket /var/run/php5-fpm.sock, it will listen on 127.0.0.1:9000 (you can use whichever port you need).

Listening on a TCP socket instead of a Unix socket was required as Apache could not proxy requests over a Unix socket at the time of this writing. That is no longer true, I believe as of Apache 2.4.10.

Configure Apache

First, if you need to, install Apache:

$ sudo add-apt-repository -y ppa:ondrej/apache2
$ sudo apt-key update
$ sudo apt-get update
$ sudo apt-get install -y apache2  # May need --force-yes

For Apache, we just need to enable mod_proxy_fcgi and add a configuration into our VirtualHost:

$ sudo a2enmod proxy_fcgi

Our virtualhost might look something like this:

<VirtualHost *:80>
    ServerName localhost
    DocumentRoot /var/www/html

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

With mod_proxy, we can simply add a line to our VirtualHost so PHP processes are proxied off to PHP-FPM:

ProxyPassMatch ^/(.*\.php(/.*)?)$ fcgi://127.0.0.1:9000/var/www/html/$1

The full VirtualHost in this example would look like this:

<VirtualHost *:80>
    ServerName localhost
    DocumentRoot /var/www/html

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

    ProxyPassMatch ^/(.*\.php(/.*)?)$ fcgi://127.0.0.1:9000/var/www/html/$1
</VirtualHost>

Let's restart Apache so both the enabled module and the edited VirtualHost take effect:

$ sudo service apache2 restart

Then any php file in /var/www/html will be handled by PHP-FPM!