Redis Sentinel is a special operating mode of Redis for monitoring running Redis master and slave instances. Redis Sentinel allows for a failing master instance to be replaced by a replicated slave and other types of failures thereby giving users of Redis a high availability option for their application. Beside monitoring and automatic failover, Redis Sentinel also provides notification options where Redis Sentinel will alert the system administrators or other programs through an API when a critical error occurs in a monitored Redis instance. Redis Sentinel also assists in operational management by being a configuration provider for client automatic discovery of services. While simple in theory, Redis Sentinel is used in very complex workflows and monitoring/failover scenarios in the Enterprise.
As a distributed system, Redis Sentinel requires at least three instances for a robust deployment. Multiple Sentinels cooperate to detect failing masters by requiring...