All 7 Redis Sentinel & High Availability questions
More in Redis Sentinel & High Availability
What is Redis Sentinel, and what role does it play in providing high availability for a non clustered Redis setup? Why does Redis Sentinel recommend running at least three Sentinel instances rather than just one? What is the quorum setting in a Sentinel configuration, and how does it affect the decision to trigger a failover? How do you check the current status of a Sentinel deployment to confirm it is properly monitoring your Redis primary and replicas? How would you deploy Redis Sentinel across multiple data centers or availability zones to maximize resilience against a localized failure? What is the difference between using Redis Sentinel and using Redis Cluster for achieving high availability, and how would you decide between them?
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How does an application discover the current primary Redis instance when using Sentinel, especially after a failover has occurred?

Intermediate

Answer

Rather than connecting directly to a specific server address, a Sentinel aware client library asks one of the Sentinel instances for the current address of the primary, and after a failover happens, subsequent queries to Sentinel automatically return the new primary's address, letting the application always connect to the correct, currently active primary.
-- Client asks Sentinel for the current primary address
SENTINEL get-master-addr-by-name mymaster
Real-world example An application configured with a Sentinel aware client library automatically reconnects to the newly promoted primary after a failover, since it always asks Sentinel for the current address rather than hardcoding a specific server.

Common follow-ups: What happens to an application's existing connections during the brief period while a failover is happening?;Do all Redis client libraries support Sentinel awareness?

Connection Pooling & Client Libraries;Redis Replication
All 7 Redis Sentinel & High Availability questions