anchor.diff:  
   [source,js]
   --------------------------------------------------
  -$ curl -XGET 'http://localhost:9200/_cluster/health?wait_for_status=yellow&timeout=50s'
  +GET /_cluster/health?wait_for_status=yellow&timeout=50s
   --------------------------------------------------
  +// CONSOLE
   
   [float]
   [[request-params]]
  
positive.code: 
  [source,js]
  --------------------------------------------------
  $ curl -XGET 'http://localhost:9200/_cluster/health/twitter?level=shards'
  --------------------------------------------------
  
negative.code: == Cluster Health
  
  The cluster health API allows to get a very simple status on the health
  of the cluster. For example, on a single node cluster with a single index
  with 5 shards and one replica, this:
  
  [source,js]
  --------------------------------------------------
  GET _cluster/health
  --------------------------------------------------
  // CONSOLE
  // TEST[s/^/PUT test1\n/]
  
  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
  }
  --------------------------------------------------
  // TESTRESPONSE[s/testcluster/docs_integTest/]
  
  The API can also be executed against one or more indices to get just the
  specified indices health:
  
  [source,js]
  --------------------------------------------------
  GET /_cluster/health/test1,test2
  --------------------------------------------------
  // CONSOLE
  // TEST[s/^/PUT test1\nPUT test2\n/]
  
  The cluster health status is: `green`, `yellow` or `red`. On the shard
  level, a `red` status indicates that the specific shard is not allocated
  