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Cluster Health

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Cluster Health

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The cluster health API allows to get a very simple status on the health of the cluster. For example, on a quiet single node cluster with a single index with 5 shards and one replica, this:

GET _cluster/health

Returns this:

{
  "cluster_name" : "testcluster",
  "status" : "yellow",
  "timed_out" : false,
  "number_of_nodes" : 1,
  "number_of_data_nodes" : 1,
  "active_primary_shards" : 5,
  "active_shards" : 5,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 5,
  "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": 50.0
}

The API can also be executed against one or more indices to get just the specified indices health:

GET /_cluster/health/test1,test2

The cluster health status is: green, yellow or red. On the shard level, a red status indicates that the specific shard is not allocated in the cluster, yellow means that the primary shard is allocated but replicas are not, and green means that all shards are allocated. The index level status is controlled by the worst shard status. The cluster status is controlled by the worst index status.

One of the main benefits of the API is the ability to wait until the cluster reaches a certain high water-mark health level. For example, the following will wait for 50 seconds for the cluster to reach the yellow level (if it reaches the green or yellow status before 50 seconds elapse, it will return at that point):

GET /_cluster/health?wait_for_status=yellow&timeout=50s

Request Parameters

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The cluster health API accepts the following request parameters:

level: Can be one of cluster, indices or shards. Controls the details level of the health information returned. Defaults to cluster.
wait_for_status: One of green, yellow or red. Will wait (until the timeout provided) until the status of the cluster changes to the one provided or better, i.e. green > yellow > red. By default, will not wait for any status.
wait_for_no_relocating_shards: A boolean value which controls whether to wait (until the timeout provided) for the cluster to have no shard relocations. Defaults to false, which means it will not wait for relocating shards.
wait_for_active_shards: A number controlling to how many active shards to wait for, all to wait for all shards in the cluster to be active, or 0 to not wait. Defaults to 0.
wait_for_nodes: The request waits until the specified number N of nodes is available. It also accepts >=N, <=N, >N and <N. Alternatively, it is possible to use ge(N), le(N), gt(N) and lt(N) notation.
timeout: A time based parameter controlling how long to wait if one of the wait_for_XXX are provided. Defaults to 30s.
local: If true returns the local node information and does not provide the state from master node. Default: false.

The following is an example of getting the cluster health at the shards level:

GET /_cluster/health/twitter?level=shards

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