集群特性

• Monitoring. Sentinel constantly checks if your master and replica instances are working as expected.

• Notification. Sentinel can notify the system administrator, or other computer programs, via an API, that something is wrong with one of the monitored Redis instances.

• Automatic failover. If a master is not working as expected, Sentinel can start a failover process where a replica is promoted to master, the other additional replicas are reconfigured to use the new master, and the applications using the Redis server are informed about the new address to use when connecting.

• Configuration provider. Sentinel acts as a source of authority for clients service discovery: clients connect to Sentinels in order to ask for the address of the current Redis master responsible for a given service. If a failover occurs, Sentinels will report the new address.

集群架构

• Masters are called M1, M2, M3, ..., Mn.

• replicas are called R1, R2, R3, ..., Rn (R stands for replica).

• Sentinels are called S1, S2, S3, ..., Sn.

1.master节点