...
Make it part of a routine to check the Swarm UI to monitor for problems with an Elasticsearch cluster.
Go Navigate to Cluster > Feeds to monitor the real-time status of the search feed. Examine the health of the Elasticsearch cluster if the Swarm search index status is yellow or red. See Search Feeds.
Go Navigate to Reports > Elasticsearch to view details and alerts. See Elasticsearch Reports in Using Cluster Reports.
Checking ES Cluster Health
...