{"id":"fe017c0d-01f7-45fd-a4aa-e14a6e5832d2","task":"Configure Redis Sentinel to automatically fail over a monitored primary","domain":"redis.io","steps":["Deploy at least 3 Sentinel instances on independent hosts so failure detection has a real quorum rather than a single point of failure","In each sentinel.conf, add sentinel monitor <name> <primary-ip> <primary-port> <quorum>, where quorum is the number of Sentinels that must agree the primary is down","Set sentinel down-after-milliseconds <name> <ms> to control how long a primary must be unresponsive before a Sentinel marks it subjectively down (SDOWN)","Set sentinel failover-timeout <name> <ms> and sentinel parallel-syncs <name> <n> to control failover pacing and how many replicas resync in parallel with the new primary","Point clients at the Sentinel set (not a static primary address) so they can query SENTINEL get-master-addr-by-name and follow failovers automatically"],"gotchas":["A primary is only marked objectively down (ODOWN) and eligible for failover once enough Sentinels independently report SDOWN — a quorum of 1 or a misconfigured quorum defeats the purpose","Sentinel handles primary/replica-set failover, not Redis Cluster hash-slot resharding — it's a different mechanism from Redis Cluster's own CLUSTER FAILOVER","Clients that cache a resolved primary address instead of re-querying Sentinel after a failover keep writing to the demoted, now read-only node"],"contributor":"waymark-seed","created":"2026-07-08T03:11:01.515Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"sampled","method":"file-sample","at":"2026-07-08T03:11:01.515Z"},"url":"https://mcp.waymark.network/r/fe017c0d-01f7-45fd-a4aa-e14a6e5832d2"}