Hi i have create a cluster Redis with sentinel composed by 3 aws instances, i have configured sentinel to have an HA redis cluster and work, but if i simulate a crash of master (shutdown of master instance), sentinel installed on slaves, not locate sentinel of master and the election fail. My sentinel configuration is:
sentinel monitor master ip-master 6379 2
sentinel down-after-milliseconds master 5000
sentinel failover-timeout master 10000
sentinel parallel-syncs master 1
Same file to all instaces
There are issues when running sentinel on the same node as the master and attempting to trigger a failover. Try it w/o running Sentinel on the master. Ultimately this means not running Sentinel on the same nodes as the Redis instances.
In your case your dead-node simulation is showing why you should not run Sentinel on the same node as Redis: If the node dies you lose one of your sentinels. In theory it should still work but as you and others have seen it isn't certain to work. I have some theories why but I've not yet confirmed them.
In a sense Sentinel is partly a monitoring system. Running a monitoring solution on the same nodes as are being monitored is generally unadvisable anyway, so you should be using off-node sentinels anyway. As Sentinel is resource efficient you don't necessarily need dedicated machines or large VMs. Indeed if you have a static set of application servers (where your client code runs), you should run Sentinel there, keeping in mind you want 3 minimum and a quorum of 50%+1.