We have an elasticsearch cluster with 3 master and 6 data nodes . Elasticsearch version is 7.6.1(OSS).
one of the data node is becoming non-responsive and none of API's (like _cat, _cluster/health etc) are working when we query directly to this node.
The overall cluster health is green and the elasticseach process is also running fine(checked using sudo service elasticsearch status).
In logs we do not find any error , other metrics like CPU, Memory,Disk IO are looking good.
How to figure out what could have gone wrong with the node and debug further?