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

Stop redis on all hosts.

service redis-server stop

Remove //var/lib/redis/nodes-6379.conf as this file is identical on all nodes, and will cause each node to have the same id

rm /var/lib/redis/nodes-6379.conf

Start redis on all hosts.

service redis-server start

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

-  ⇤ ← Revision 7 as of 2020-02-11 23:20:21 → 
  Size: 802
  Editor: Kristian Kallenberg
  Comment:
+   ← Revision 24 as of 2021-01-02 01:39:31 → ⇥
  Size: 2440
  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 redis-cli
+apt-get install redis-server
-Line 19:
+Line 21:
-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.
+=== Redis Server ===
-Line 21:
+Line 23:
+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.
-Line 25:
+Line 30:
-The same goes for `/etc/redis/sentinel.conf`
+Enable redis to listen on the network, instead of only listening on the loopback device.
-Line 27:
+Line 33:
-bind 127.0.0.1 192.168.1.58
+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
}}}

Stop redis on all hosts.
{{{
service redis-server stop
}}}

Remove `//var/lib/redis/nodes-6379.conf` as this file is identical on all nodes, and will cause each  node to have the same id
{{{
rm /var/lib/redis/nodes-6379.conf
}}}

Start redis on all hosts.
{{{
service redis-server start
}}}

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
-Line 34:
+Line 72:
+ * 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/
 * https://www.tecmint.com/setup-redis-cluster-in-centos-8/

Redis

Software

Configuration

Redis Server

References