Redis Sentinel

When a master node experiences issues, one of its slave nodes needs to be promoted to master, and all the other slaves need to be reconfigured to point to the new master. Before Redis Sentinel, this failover process was done manually, which was not very reliable.

Redis Sentinel is a distributed system designed to automatically promote a Redis slave to master if the existing master fails. Sentinel does not distribute data across nodes since the master node has all of the data and the slaves have a copy of the data—Sentinel is not a distributed data store.

The most common architecture contains an installation of one Sentinel for each Redis server. Sentinel is a separate process from the Redis server, and it listens on its own port.

Note

If a firewall is configured in your setup, it needs to allow Sentinel to connect to all other Sentinels and Redis servers in the group.

If your architecture has one master and two replicas, you can use Sentinel in the following way:

Without Sentinel...