[[cluster-health]]
== Cluster Health

The cluster health API allows to get a very simple status on the health
of the cluster.

[source,js]
--------------------------------------------------
$ curl -XGET 'http://localhost:9200/_cluster/health?pretty=true'
{                                                                                            
  "cluster_name" : "testcluster",                                                              
  "status" : "green",                                                                        
  "timed_out" : false,                                                                       
  "number_of_nodes" : 2,                                                                     
  "number_of_data_nodes" : 2,                                                                
  "active_primary_shards" : 5,                                                               
  "active_shards" : 10,                                                                      
  "relocating_shards" : 0,                                                                   
  "initializing_shards" : 0,                                                                 
  "unassigned_shards" : 0,
  "number_of_pending_tasks" : 0
}
--------------------------------------------------

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

[source,js]
--------------------------------------------------
$ curl -XGET 'http://localhost:9200/_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):

[source,js]
--------------------------------------------------
$ curl -XGET 'http://localhost:9200/_cluster/health?wait_for_status=yellow&timeout=50s'
--------------------------------------------------

[float]
[[request-params]]
=== Request Parameters

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_relocating_shards`::
    A number controlling to how many relocating
    shards to wait for. Usually will be `0` to indicate to wait till all
    relocations have happened. Defaults to not wait.
    
`wait_for_active_shards`::
    A number controlling to how many active
    shards to wait for. Defaults to not wait.

`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`.


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

[source,js]
--------------------------------------------------
$ curl -XGET 'http://localhost:9200/_cluster/health/twitter?level=shards'
--------------------------------------------------
