One of the customer has only 2 nodes cluster ( and don't want to add 3rd node) which becomes inaccessible for 2-3 mins, if first node (master) goes down. Below is the error which user face :-
SearchPhaseExecutionException: Failed to execute phase [query_fetch], all shards failed
And after few mins (2-3 mins) second nodes takes the charge and it start responding to incoming requests.
Since, we can't force user to add 3rd node in cluster and they need second node just for fault tolerance purpose, so can we suggest user to wait till he gets "SearchPhaseExecutionException" or any such exception. Once the another node sends master alive signal/response then he can start sending requests.