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Introducation
Redis is an in-memory data storage that is used by the CoreOne Suite. This how-to gives you a brief overview on how to install and configure a Redis-Cluster a redis cluster on Ubuntu.
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Step 1 - Check your prerequisits
Redis has to be installed on a Linux OS (Ubuntu, Redhat, Centos, etc.).
To install Redis, at least 3 instances are needed. The instances can be distributed across different servers, or concentrated on one (best practice will be shown in the examples below).
If the servers for Redis are in different network-zones, the servers must be able to communicate with eachother.
The following Firewall-Ports must be open:
6379
16384
16379
7001 (Cluster)
7002 (Cluster)
7003 (Cluster)
7004 (Cluster)
7006 (FCluster)
Example
In our example we got 3 virtual Ubuntu-Servers.
Redis HA 1 (192.168.17.134)
Redis HA 2 (192.168.17.135)
Redis HA 3 (192.168.17.136)
On Redis HA1 is a Master Instance 7001 and a Slave Instance 7004
On Redis HA2 is a Master Instance 7002 and a Slave Instance 7005
On Redis HA3 is a Master Instance 7003 and a Slave Instance 7006
For the Master 7001 the Slave is 7006
For the Master 7002 the Slave is 7006
For the Master 7003 the Slave is 7004
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Step 2 - Installation
General installation for all 3 servers:
Switch to root user:
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sudo su |
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cd /etc/redis/redis-6.2.6/ sudo make test |
Step 3 - Configuration VM 1
In our example we have multiple redis instanced on one server. This means we need multiple config-files on the server as well.
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port 7001 cluster-enabled yes cluster-config-file cluster-node-1.conf cluster-node-timeout 5000 appendonly yes appendfilename node-1.aof dbfilename dump-1.rdb |
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vim: Save file ctrl+c | wq! |
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sudo vim node4.conf |
Copy the following text to the config file:
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port 7004 cluster-enabled yes cluster-config-file cluster-node-4.conf cluster-node-timeout 5000 appendonly yes appendfilename node-4.aof dbfilename dump-4.rdb |
Step 4 - Configuration VM 2
In our example we have multiple redis instanced on one server. This means we need multiple config-files on the server as well.
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port 7002 cluster-enabled yes cluster-config-file cluster-node-2.conf cluster-node-timeout 5000 appendonly yes appendfilename node-2.aof dbfilename dump-2.rdb |
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vim: Save file ctrl+c | wq! |
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sudo vim node5.conf |
Copy the following text to the config file:
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port 7005 cluster-enabled yes cluster-config-file cluster-node-5.conf cluster-node-timeout 5000 appendonly yes appendfilename node-5.aof dbfilename dump-5.rdb |
Step 5 - Configuration VM 3
In our example we have multiple redis instanced on one server. This means we need multiple config-files on the server as well.
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port 7003 cluster-enabled yes cluster-config-file cluster-node-3.conf cluster-node-timeout 5000 appendonly yes appendfilename node-3.aof dbfilename dump-3.rdb |
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vim: Save file ctrl+c | wq! |
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sudo vim node6.conf |
Copy the following text:
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port 7006 cluster-enabled yes cluster-config-file cluster-node-6.conf cluster-node-timeout 5000 appendonly yes appendfilename node-6.aof dbfilename dump-6.rdb |
Step 6 - Start Redis
We can start Redis now on each VM through the config-files we created.
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Server | Instanz | Befehl | ||||
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HA1 (192.168.17.134) | Node 01 - Port 7001 Node 04 - Port 7004 |
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HA 2 (192.168.17.135) | Node 02 - Port 7002 Node 05 - Port 7005 |
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HA 3 (192.168.17.136) | Node 03 - Port 7003 Node 06 - Port 7006 |
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Step 7 - Connect Redis
We can now connect on each instace with the Redis-CLI
Server | Instanz | Befehl | ||
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HA1 (192.168.17.134) | Node 01 - Port 7001 Node 04 - Port 7004 |
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HA 2 (192.168.17.135) | Node 02 - Port 7002 Node 05 - Port 7005 |
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HA 3 (192.168.17.136) | Node 03 - Port 7003 Node 06 - Port 7006 |
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Step 8 - Configure Redis Cluster
Since the instaces are local at the moment, we need to connect them to the cluster.
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Check the config and confirm with: Y
Step 9 - Redis-CLI
Open Redis-CLI:
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-p = Port -c = Cluster |
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./redis-6.2.6/src/redis-cli -c -p 7001 |
ping
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ping |
The different nodes can be pinged:
info
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info |
Shows all information on the cluster
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cluster nodes
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cluster nodes |
Shows all nodes and if they are master or slave.
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info replication
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info replication |
Shows if the server is master or slave. Shows the depending slaves.
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Step 10 - Failover
We will terminate Master 7003 for this example. This will prompt the Slave 7004 to become the new master:
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On the masters 7001 and 7002 we will get the following message:Code Block
We can now check with the Redis-CLI. With the command “Cluster nodes”, we can see, Slave 7004 is now a Master.
We can also see that Master 7003 can’t be reached.
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If you want the 7003 as Master again, use the following command:
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./redis-6.2.6/src/redis-cli -c -p 7003
cluster failover |
Message:
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127.0.0.1:7003> 17830:S 26 Apr 2022 14:07:57.685 # Received replication offset for paused master manual failover: 589308 17830:S 26 Apr 2022 14:07:57.685 # All master replication stream processed, manual failover can start. 7830:S 26 Apr 2022 14:07:57.685 # Start of election delayed for 0 milliseconds (rank #0, offset 589308). 17830:S 26 Apr 2022 14:07:57.685 # Starting a failover election for epoch 29. 17830:S 26 Apr 2022 14:07:57.686 # Currently unable to failover: Waiting for votes, but majority still not reached. 17830:S 26 Apr 2022 14:07:57.686 # Failover election won: I'm the new master. 17830:S 26 Apr 2022 14:07:57.686 # configEpoch set to 29 after successful failover 17830:M 26 Apr 2022 14:07:57.686 # Connection with master lost. 17830:M 26 Apr 2022 14:07:57.686 * Caching the disconnected master state. 17830:M 26 Apr 2022 14:07:57.686 * Discarding previously cached master state. 17830:M 26 Apr 2022 14:07:57.686 # Setting secondary replication ID to 897d8ffc57482c31a6d37db92136073b713e813e, valid up to offset: 589309. New replication ID is 17e90a8ddf3d4fd645d4ec162267629a4109ea9f |
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