[antirez]

Hey, going a bit off topic about Sentinel, this should not happen. Sentinel + Redis + Clients as a distributed system is not able to guarantee strong consistency with arbitrary partitions clearly, but in the scenario you describe, that is, the master crashes or is partitioned away alone, the window should be like a fraction of a millisecond (the replication link latency) most of the times.

EDIT: to clarify:

1) Sentinels will tell clients master is A.

2) A fails.

3) Sentinels will still tell it is A before failover.

4) Failover happens.

5) Sentinels will finally tell master is B.

[taf2]

could be something that haproxy is causing - when switching masters... maybe I need a script that handles switching the vip when sentinel detects failure in master instead of haproxy with a backup... btw - thank you for redis.

[seiji]

You shouldn't need haproxy in the loop at all.

If your redis client is Sentinel-aware, you ask your client directly "give me the redis master server" and it asks Sentinel which server is master. The only ip address involved for your configuration is the address of the sentinel(s).

haproxy will take 30 seconds to detect your failure. Sentiel will notify you immediately. Sentinel is the one determining the exact state of the master election, and it'll be very chatty when a new master replaces the old one.