This tutorial tries to provide information about the availability and consistency characteristics of Redis Cluster from the point of view of the final user, stated in a simple to understand way
The architecture of redis cluster
In practical terms, Redis Cluster provides the ability to
- Automatically split your dataset among multiple nodes.
- Continue operations when a subset of the nodes are experiencing failures or are unable to communicate with the rest of the cluster.
The Mechanism
When client API writes to the Master A then Master A replies OK to client API. The Master A propagates the write to its Slaves A, B and C.
When Master A fails then Slave A will be promoted as new master.
$ wget http://download.redis.io/releases/redis-5.0.4.tar.gz
$ tar xzf redis-5.0.4.tar.gz
$ cd redis-5.0.4
$ make
The binaries that are now compiled are available in the
src directory. filename: redis-node1.conf
port 7001
cluster-enabled yes
cluster-config-file rediscluster-node-1.conf
cluster-node-timeout 5000
appendonly yes
appendfilename node-1.aof
dbfilename dump-1.rdb
filename: redis-node2.conf
port 7002
cluster-enabled yes
cluster-config-file rediscluster-node-2.conf
cluster-node-timeout 5000
appendonly yes
appendfilename node-2.aof
dbfilename dump-2.rdb
Please continue by creating other node configuration file, just change the port and the number according to the sequence of the port for easy setup. Then copy the configuration file to each node.
Implementing in 1 node (localhost)
If you run only 1 node then you have to create 6 folder and putting redis code in each folder then compile the code. In my case, the folder will look like this:
/home/api/redis1/redis-5.0.4/src
/home/api/redis2/redis-5.0.4/src
/home/api/redis3/redis-5.0.4/src
/home/api/redis4/redis-5.0.4/src
/home/api/redis5/redis-5.0.4/src
/home/api/redis6/redis-5.0.4/src
Don't forget to copy the configuration file into each folder.
Run the Redis server in each folder in different terminal tab:
$ /home/api/redis1/redis-5.0.4/src/redis-server redis-node1.conf
$ /home/api/redis2/redis-5.0.4/src/redis-server redis-node2.conf
$ /home/api/redis3/redis-5.0.4/src/redis-server redis-node3.conf
$ /home/api/redis4/redis-5.0.4/src/redis-server redis-node4.conf
$ /home/api/redis5/redis-5.0.4/src/redis-server redis-node5.conf
$ /home/api/redis6/redis-5.0.4/src/redis-server redis-node6.conf
Then create the cluster by using tools in redis utils in folder /home/api/redis6/redis-5.0.4/src/utils:
$ /home/api/redis/redis-5.0.4/utils/create-cluster/create-cluster start
$ /home/api/redis/redis-5.0.4/utils/create-cluster/create-cluster create
To stiop redis cluster:
$ /home/api/redis/redis-5.0.4/utils/create-cluster/create-cluster stop
create-cluster command
Or you can create redis cluster by running this command:
$ /home/api/redis6/redis-5.0.4/src/redis-cli --cluster create 127.0.0.1:7001 \
127.0.0.1:7002 127.0.0.1:7003 127.0.0.1:7004 127.0.0.1:7005 127.0.0.1:7006 \
--cluster-replicas 1
Since redis cluster run in 1 node, make sure you use different port for each redis-server and granted each port.
Implementing in multiple node
If you run in multiple nodes, just run this command and make sure the IP address each node is correct:
$ /home/api/redis6/redis-5.0.4/src/redis-cli --cluster create 10.10.16.124:7001 10.10.16.125:7001 10.10.16.126:7001 10.10.16.127:7001 10.10.16.128:7001 10.10.16.129:7001 --cluster-replicas 1
Since redis cluster run in multiple node, you can use same port number for redis-server and granted the port.
Testing Fail Over
The easy way to test redis cluster by open new terminal and run redis-cli
$ redis-cli -c -p 7001
redis 127.0.0.1:7001> set foo bar
-> Redirected to slot [12182] located at 127.0.0.1:7002
OK
redis 127.0.0.1:7002> set hello world
-> Redirected to slot [866] located at 127.0.0.1:7001
OK
redis 127.0.0.1:7001> get foo
-> Redirected to slot [12182] located at 127.0.0.1:7002
"bar"
redis 127.0.0.1:7001> get hello
-> Redirected to slot [866] located at 127.0.0.1:7000
"world"$ redis-cli -c -p 7001
redis 127.0.0.1:7001> cluster nodes Thank you
