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.

• 192.168.1.58 redis01
• 192.168.1.59 redis02
• 192.168.1.60 redis03

Software

apt-get install redis-server redis-sentinel

Configuration

Redis Server

Make sure the apache servers can reach redis. Change bind 127.0.0.1 in /etc/redis/redis.conf. Each of the redis servers needs to listen on its own IP-address.

bind 127.0.0.1 192.168.1.58

Stop the redis server on all hosts.

service redis-server stop

To enable replication we need to consider one of the redis servers the master. Here it will be redis01. On the two other hosts add the following to /etc/redis/redis.conf.

slaveof 192.168.1.58 6379

Start the redis servers again, but start it on redis01 first.

service redis-server start

redis01 should now be the master.

Redis Sentinel

The same goes for /etc/redis/sentinel.conf

bind 127.0.0.1 192.168.1.58

References

• https://redis.io/topics/sentinel

• https://redis.io/topics/replication

• https://www.haproxy.com/blog/haproxy-advanced-redis-health-check/

• https://medium.com/@amila922/redis-sentinel-high-availability-everything-you-need-to-know-from-dev-to-prod-complete-guide-deb198e70ea6

• https://blog.usejournal.com/first-step-to-redis-cluster-7712e1c31847

• https://www.linode.com/docs/applications/big-data/how-to-install-and-configure-a-redis-cluster-on-ubuntu-1604/

• https://www.willandskill.se/en/setup-a-highly-available-redis-cluster-with-sentinel-and-haproxy/