Order to understand how exactly Sentinel works. Properties of Sentinel, to more complex information (that are optional) in Starting from basic information needed in order to understand the basic In this document concepts will be introduced gradually The sum of Sentinels, Redis instances (masters and replicas) and clientsĬonnecting to Sentinel and Redis, are also a larger distributed system with There is no fun in having a failover system which is itself a single point of failure, after all. Sentinel works even if not all the Sentinel processes are working, making the system robust against failures.This lowers the probability of false positives. Failure detection is performed when multiple Sentinels agree about the fact a given master is no longer available.The advantage of having multiple Sentinel processes cooperating are the following: Sentinel itself is designed to run in a configuration where there are multiple Sentinel processes cooperating together. If a failover occurs, Sentinels will report the new address. 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 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. Sentinel can notify the system administrator, or other computer programs, via an API, that something is wrong with one of the monitored Redis instances. Sentinel constantly checks if your master and replica instances are working as expected.
#Sentinel node full#
This is the full list of Sentinel capabilities at a macroscopic level (i.e. Notifications and acts as a configuration provider for clients. Redis Sentinel also provides other collateral tasks such as monitoring, Redis Sentinel provides high availability for Redis when not using Redis Cluster. High availability for non-clustered Redis
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