Health status of the cluster, based on the state of its primary and replica shards. Statuses are:
green
All shards are assigned.
yellow
All primary shards are assigned, but one or more replica shards are unassigned. If a node in the cluster fails, some data could be unavailable until that node is repaired.
red
One or more primary shards are unassigned, so some data is unavailable. This can occur briefly during cluster startup as primary shards are assigned.