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.

192.168.1.59 redis01
192.168.1.60 redis02
192.168.1.61 redis03

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.

bind 127.0.0.1 192.168.1.58

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 the redis server on all hosts.

service redis-server restart

-  ⇤ ← Revision 9 as of 2020-02-11 23:58:15 → 
  Size: 1269
  Editor: Kristian Kallenberg
  Comment:
+   ← Revision 21 as of 2021-01-02 01:26:04 → ⇥
  Size: 1996
  Editor: Kristian Kallenberg
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
 Line 1:
+DISCLAIMER
THIS ONLY WORKS IN BUSTER
-Line 7:
+Line 9:
- * 192.168.1.58 redis01
 * 192.168.1.59 redis02
 * 192.168.1.60 redis03
+ * 192.168.1.59 redis01
 * 192.168.1.60 redis02
 * 192.168.1.61 redis03
-Line 14:
+Line 16:
-apt-get install redis-server redis-sentinel
+apt-get install redis-server
-Line 21:
+Line 23:
-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.
+Change the contents of the redis configuration file in `/etc/redis/redis.conf`.
-Line 23:
+Line 25:
+Add the IP-address for each of the servers. Each of the redis servers needs to listen on its own IP-address.
-Line 27:
+Line 30:
-Stop the redis server on all hosts.
+Enable redis to listen on the network, instead of only listening on the loopback device.
-Line 29:
+Line 33:
-service redis-server stop
+protected-mode no
-Line 32:
+Line 36:
-To enable replication we need to consider one of the redis servers the master. Here it will be redis03. On the two other hosts add the following to `/etc/redis/redis.conf`.
+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.
-Line 34:
+Line 38:
-slaveof 192.168.1.60 6379
+appendonly yes
-Line 37:
+Line 41:
-Start the redis servers again, but start it on redis03 first.
+Activate redis cluster features
-Line 39:
+Line 43:
-service redis-server start
+cluster-enabled yes
cluster-config-file nodes-6379.conf
cluster-node-timeout 15000
-Line 41:
+Line 47:
-redis03 should now be the master.
-Line 43:
+Line 48:
-=== Redis Sentinel ===

The same goes for `/etc/redis/sentinel.conf`
+Restart the redis server on all hosts.
-Line 47:
+Line 50:
-bind 127.0.0.1 192.168.1.58
+service redis-server restart
-Line 54:
+Line 57:
+ * 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/
 * https://www.tecmint.com/setup-redis-replication-in-centos-8/
 * https://www.tecmint.com/setup-redis-high-availability-with-sentinel-in-centos-8/

Redis

Software

Configuration

Redis Server

References