Redis cluster mode construction

Redis clustering mode is a mechanism that improves scalability and availability by sharding Redis instances on multiple servers. Here are the steps to build a Redis cluster mode:

1. Create a Redis instance

• Create at least 6 Redis instances, and it is recommended to use an odd number to avoid split brain problems.
• Name the instances redis-node-1, redis-node-2, etc.
• The ports configured for each instance are different, such as: 6379, 6380, 6381, etc.

2. Configure sentinel instance

• Create 3 sentinel instances that are responsible for monitoring Redis instances and failover.
• Name the sentinel instance sentinel-node-1, sentinel-node-2, and sentinel-node-3.
• The ports configured with sentinel instances are different, such as: 26379, 26380, 26381, etc.

3. Configure the sentinel configuration file

• Create a configuration file for each sentinel instance, for example: sentinel-node-1.conf.
• In the configuration file, add the following configuration:

 <code>sentinel monitor <master-name> <master-ip> <master-port> <quorum> sentinel down-after-milliseconds <master-name> <milliseconds> sentinel failover-timeout <master-name> <milliseconds></milliseconds></master-name></milliseconds></master-name></quorum></master-port></master-ip></master-name></code>

• in:

  • <master-name></master-name> is the name of the master Redis instance.
  • <master-ip></master-ip> is the IP address of the master Redis instance.
  • <master-port></master-port> is the port of the master Redis instance.
  • <quorum></quorum> is the number of sentinel instances required to grant the ballot to the new elector, and the recommended value is (sentinel instance number/2) 1.
  • <milliseconds></milliseconds> is the number of milliseconds to mark the master as downtime after no response from the master is received within the specified time.
  • <failover-timeout></failover-timeout> is the number of milliseconds to wait for the master to reconnect before starting the failover.

4. Configure Redis instance

• In the configuration file for each Redis instance, add the following configuration:

 <code>cluster-enabled yes cluster-config-file nodes.conf</code>

• in:

  • cluster-enabled enables cluster mode.
  • cluster-config-file specifies the file path that contains cluster information.

5. Create nodes.conf file

• Create a file named nodes.conf and place it in the configuration file directory of each Redis instance.
• In the file, add the following information:

 <code><node-id> <host> <port> <node-id> <host> <port> ...</port></host></node-id></port></host></node-id></code>

• in:

  • <node-id></node-id> is a unique identifier for the Redis instance in the format ":" or "".
  • <host></host> is the IP address or host name of the Redis instance.
  • <port></port> is the port of the Redis instance.

6. Start the cluster

• Start all Redis and sentinel instances.
• On any Redis instance, execute the following command:

 <code>redis-cli --cluster create <nodes.conf path> <replicas></replicas></nodes.conf></code>

• in:

  • <nodes.conf path></nodes.conf> is the path to the nodes.conf file.
  • <replicas></replicas> Specifies the number of each master replica.

7. Verify the cluster

• Log in to any Redis instance in the cluster and execute the CLUSTER INFO command.
• Check whether the cluster_state field is ok to indicate that the cluster has been successfully established.

8. Use clusters

• You can use clusters like you would with a single Redis instance.
• Use cluster-keyslot command to get the slot where the key should be located, and then send the command to the Redis instance corresponding to the slot.

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