= Apache =

Running a redundant apache server does not require much from apache itself, but rather the underlying filesystem and a proxy in front of it. The filesystem is important, so the website can be shared between the servers. For this we will use [[GlusterFS|GlusterFS]]. PHP sessions will have to be shared between the webservers too. [[Redis|Redis]] will be used for that and finally we will put a proxy in front of apache, which will be a combination of [[Corosync and HA-proxy|Corosync and HA-proxy]].

In this setup we will configure 2 apache servers. None of these will be master/slave/primary/secondary. They will just be running with the same configuration.

 * 192.168.1.47 www (virtual IP-address)
 * 192.168.1.48 www01
 * 192.168.1.49 www02

== Software ==

{{{
apt-get install apache2 php php-mysql php-redis
}}}

== Filesystem ==

Configure your system as a [[GlusterFS Client|GlusterFS client]], so you have the following in your fstab.
{{{
/etc/glusterfs/www.vol /var/www glusterfs defaults,_netdev,rw 0 0
}}}

== PHP Sessions ==

Creating a PHP session on one webserver, does not create it on the other. As requests bounces back and forth between the two webservers, this will be a problem for PHP sites. A solution to this is using [[Redis|Redis]] as a storage for the PHP sessions.

In `/etc/php/7.0/apache2/php.ini` and `/etc/php/7.0/cli/php.ini` find the entry `session.save_handler = files` and change it to the following.
{{{
session.save_handler = redis
session.save_path = "tcp://redis:6379"
}}}

Copy the configuration to all webservers and finally restart the services.
{{{
service apache2 restart
}}}

== Testpage ==
Make a simple webpage, that shows something unique about the system and also creates a PHP-session. Use this to test the setup.

`index.php`
{{{#!highlight php
<?php
        header('Content-Type: text/plain');
        session_start();
        if(!isset($_SESSION['visits']))
                $_SESSION['visits'] = 0;
        $_SESSION['visits']++;
        echo "client: " . $_SERVER['REMOTE_ADDR'] . "\n";
        echo "server: " . $_SERVER['SERVER_ADDR'] . "\n";
        echo "hostname: " . gethostname() . "\n";
        echo "visits: " . $_SESSION['visits'] . "\n";
        echo "cookie: ";
        if (array_key_exists('PHPSESSID', $_COOKIE))
                echo $_COOKIE['PHPSESSID'];
        echo "\n";
?>
}}}

== References ==

 * https://www.digitalocean.com/community/tutorials/how-to-set-up-a-redis-server-as-a-session-handler-for-php-on-ubuntu-14-04