DISCLAIMER THIS ONLY WORKS IN BUSTER INCOMPLETE DO NOT USE

Redis

Redis is an in memory data structure storage. It will be used to share PHP-sessions between the apache servers. To guarantee a robust deployment three redis servers will be configured.

Software

apt-get install redis-server

Configuration

Redis Server

Change the contents of the redis configuration file in /etc/redis/redis.conf.

Add the IP-address for each of the servers. Each of the redis servers needs to listen on its own IP-address. Due to a bug in redis, the added IP-address will have to be in the beginning of the line, right next to bind. If the IP-address is added in the end of the line, then the cluster will not initialize itself, and a Waiting for the cluster to join... message will continuously write dots. 

bind 192.168.1.58 127.0.0.1 ::1

Enable redis to listen on the network, instead of only listening on the loopback device. 

protected-mode no

Redis stores its data in memory only, hence its speed. To make sure redis does not loose its state, in case of a hardware failure, this will enable it to store the state as it changes in a file on disk. 

appendonly yes

Activate redis cluster features 

cluster-enabled yes
cluster-config-file nodes-6379.conf
cluster-node-timeout 15000

Restart redis on all hosts. 

service redis-server restart

Next we will need to configure the servers to run as a cluster 

redis-cli --cluster create 192.168.1.59:6379 192.168.1.60:6379 192.168.1.61:6379

References