Identify if sentinel node is down

[Vikas goyal Goal]

Hi,

I have redis sentinel setup with 5 sentinels. 

I want to the monitoring of REDIS HA. For this I want to check if any of the sentinel instance is down.  Is there any command which can tell me if any of the sentinel instance is down? 

I will use that command in one shell script to check if any Sentinel instance goes down. 

I tried "info sentinel" but this gives number of configured sentinel. It does not give the status of any particular sentinel instance if it is down.

Regards,

Vikas

[Manish Arora]

You only need to specify the masters to monitor, giving to each separated master (that may have any number of replicas) a different name. There is no need to specify replicas, which are auto-discovered. 

sentinel monitor <master-group-name> <ip> <port> <quorum>

For example:

sentinel monitor mymaster 127.0.0.1 6379 2 

sentinel down-after-milliseconds mymaster 60000 

sentinel failover-timeout mymaster 180000 

sentinel parallel-syncs mymaster 1 

sentinel monitor resque 192.168.1.3 6380 4 

sentinel down-after-milliseconds resque 10000 

sentinel failover-timeout resque 180000 

sentinel parallel-syncs resque 5

Sentinel will update the configuration automatically with additional information about replicas (in order to retain the information in case of restart). The configuration is also rewritten every time a replica is promoted to master during a failover and every time a new Sentinel is discovered.

The example configuration above basically monitors two sets of Redis instances, each composed of a master and an undefined number of replicas. One set of instances is called mymaster, and the other resque.

For more details, you may refer to the following documentation: https://redis.io/topics/sentinel 

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[Manish Arora]

My response is a bit delayed. I realized your question was slightly different. You were asking about how to do a health check on sentinels. 

Option 1:

From the CLI you can run the following command to get the state of Sentinel

SENTINEL SENTINELS <master name> Show a list of sentinel instances for this master, and their state.

Option 2:

From the master, you can look for:

$ redis-cli -p 5000 

127.0.0.1:5000> sentinel master mymaster

filter for "num-other-sentinels" this will tell you how many Sentinels master knows off. 

Manish