Distributed computing: sentinel、cluster

Redis sentinel、Redis cluster都属于distributed system，其中使用了很多distributed computing中的技术，我们可以将Redis作为学习distributed computing的一个非常好的案例，也可以使用distributedcomputing的理论来对它进行分析；

Redis sentinel、Redis cluster

Redis sentinel、Redis cluster都属于distributed system存在着诸多共同之处，可以认为: Redis cluster集成了Redis sentinel的功能。

	Redis sentinel	Redis cluster
Consensus protocol	raft	raft
	current epoch、config epoch	current epoch、config epoch
下线	主观下线、客观下线	疑似下线、下线
system/topology state	`sentinelState`	`clusterState`
auto discover	HELLO channel	gossip

stackoverflow Redis sentinel vs clustering

fnordig Redis Sentinel & Redis Cluster - what?

Redis Sentinel

It will monitor your master & slave instances, notify you about changed behaviour, handle automatic failover in case a master is down and act as a configuration provider, so your clients can find the current master instance.

NOTE:

上面这段话，介绍了"configuration provider"的功能

Redis Cluster

Redis Cluster is a data sharding solution with automatic management, handling failover and replication.

CAP

Redis的两种部署方式(sentinel、cluster)都属于distributed system，都涉及CAP:

consistency、availability、partition；