Elasticsearch:View the health status of an Elasticsearch cluster

Check cluster health

1. Log on to the Kibana console of your Elasticsearch cluster. For more information, see Log on to the Kibana console.

2. In the left-side navigation pane, click Dev Tools.

3. On the Console tab, run the following command:

   GET /_cluster/health

   A successful response looks similar to the following:

   {
     "cluster_name" : "es-cn-45xxxxxxxxxxxxk1q",
     "status" : "green",
     "timed_out" : false,
     "number_of_nodes" : 2,
     "number_of_data_nodes" : 2,
     "active_primary_shards" : 18,
     "active_shards" : 36,
     "relocating_shards" : 0,
     "initializing_shards" : 0,
     "unassigned_shards" : 0,
     "delayed_unassigned_shards" : 0,
     "number_of_pending_tasks" : 0,
     "number_of_in_flight_fetch" : 0,
     "task_max_waiting_in_queue_millis" : 0,
     "active_shards_percent_as_number" : 100.0
   }

4. Check the status field to determine cluster health. If the status is green, no action is needed. If the status is yellow or red, recover the affected indexes before performing other operations.

   Status	Shard allocation	Operational impact
   green	All primary and replica shards are assigned	Cluster is fully operational
   yellow	All primary shards are assigned, but one or more replica shards are unassigned	Cluster is operational but not fully redundant. Operations such as password changes and cluster configuration upgrades take longer to complete
   red	One or more primary shards are unassigned	Some data is unavailable

Recover a yellow cluster

A cluster enters yellow state when replica shards cannot be assigned — typically because the configured replica count exceeds the number of available nodes minus one. For example, if your cluster has three nodes and an index is configured with three replica shards per primary shard, the replica shards cannot all be assigned and the cluster becomes yellow.

Follow these steps to locate and fix the affected index.

1. Query the status of all indexes to identify which index has unassigned replica shards:

   curl -u <username>:<password> http://<host>:9200/_cat/indices

   In the output, find the index with a yellow status. That index has unassigned replica shards.

   

2. Reduce the replica count for the affected index so it does not exceed the number of nodes minus one:

   curl -XPUT -u <username>:<password> http://<host>:9200/<index-name>/_settings -H 'Content-Type: application/json' -d '{"index":{"number_of_replicas":(<number-of-nodes - 1>)}'

   For example, if your cluster has three nodes, set number_of_replicas to 2.

   Replace the following placeholders:

   Placeholder	Description
   <username>	Your Kibana username
   <password>	Your Kibana password
   <host>	The endpoint of your cluster
   <index-name>	The name of the index with unassigned replica shards
   <number-of-nodes - 1>	The number of data nodes in your cluster minus one