Usefull Commands

Returns a nice status of the cluster including how many / which nodes are masters. Shows node names, heap usage and ram%

/_cat/nodes?v

View the shards in the cluster to see their health and where they've been allocated. This will also give you disk space usage

/_cat/shards?v

Get stats about all the nodes in the current cluster. (See: https://www.elastic.co/guide/en/elasticsearch/guide/current/_monitoring_individual_nodes.html )

/_nodes/stats?v

This is important to be able to monitor the cluster health. Yellow: Unallocated shards (can allocate replica on same node), Red: Missing data (Maybe a shard not started or lost?)

/_cat/health

To list the stored indicies / aliases for indicies

/_aliases

To show JVM stats, (memory usage etc)

/_nodes/jvm?pretty

Note:
Using index aliases to name the index as tweets_v1 then getting the application to use “tweets” means that it is easier to change indices later with no downtime.