Task Management API

The task management API allows to retrieve information about the tasks currently executing on one or more nodes in the cluster.

GET _tasks 
GET _tasks?nodes=nodeId1,nodeId2 
GET _tasks?nodes=nodeId1,nodeId2&actions=cluster:* 

The result will look similar to the following:

{
  "nodes" : {
    "oTUltX4IQMOUUVeiohTt8A" : {
      "name" : "H5dfFeA",
      "transport_address" : "127.0.0.1:9300",
      "host" : "127.0.0.1",
      "ip" : "127.0.0.1:9300",
      "tasks" : {
        "oTUltX4IQMOUUVeiohTt8A:124" : {
          "node" : "oTUltX4IQMOUUVeiohTt8A",
          "id" : 124,
          "type" : "direct",
          "action" : "cluster:monitor/tasks/lists[n]",
          "start_time_in_millis" : 1458585884904,
          "running_time_in_nanos" : 47402,
          "cancellable" : false,
          "parent_task_id" : "oTUltX4IQMOUUVeiohTt8A:123"
        },
        "oTUltX4IQMOUUVeiohTt8A:123" : {
          "node" : "oTUltX4IQMOUUVeiohTt8A",
          "id" : 123,
          "type" : "transport",
          "action" : "cluster:monitor/tasks/lists",
          "start_time_in_millis" : 1458585884904,
          "running_time_in_nanos" : 236042,
          "cancellable" : false
        }
      }
    }
  }
}

It is also possible to retrieve information for a particular task:

GET _tasks/task_id:1 

Or to retrieve all children of a particular task:

GET _tasks?parent_task_id=parentTaskId:1 

You can also use the detailed request parameter to get more information about the running tasks. This is useful for telling one task from another but is more costly to execute. For example, fetching all searches using the detailed request parameter:

GET _tasks?actions=*search&detailed

might look like:

{
  "nodes" : {
    "oTUltX4IQMOUUVeiohTt8A" : {
      "name" : "H5dfFeA",
      "transport_address" : "127.0.0.1:9300",
      "host" : "127.0.0.1",
      "ip" : "127.0.0.1:9300",
      "tasks" : {
        "oTUltX4IQMOUUVeiohTt8A:464" : {
          "node" : "oTUltX4IQMOUUVeiohTt8A",
          "id" : 464,
          "type" : "transport",
          "action" : "indices:data/read/search",
          "description" : "indices[test], types[test], search_type[QUERY_THEN_FETCH], source[{\"query\":...}]",
          "start_time_in_millis" : 1483478610008,
          "running_time_in_nanos" : 13991383,
          "cancellable" : true
        }
      }
    }
  }
}

The new description field contains human readable text that identifies the particular request that the task is performing such as identifying the search request being performed by a search task like the example above. Other kinds of task have have different descriptions, like _reindex which has the search and the destination, or _bulk which just has the number of requests and the destination indices. Many requests will only have an empty description because more detailed information about the request is not easily available or particularly helpful in identifying the request.

The task API can also be used to wait for completion of a particular task. The following call will block for 10 seconds or until the task with id oTUltX4IQMOUUVeiohTt8A:12345 is completed.

GET _tasks/oTUltX4IQMOUUVeiohTt8A:12345?wait_for_completion=true&timeout=10s

You can also wait for all tasks for certain action types to finish. This command will wait for all reindex tasks to finish:

GET _tasks?actions=*reindex&wait_for_completion=true&timeout=10s

Tasks can be also listed using _cat version of the list tasks command, which accepts the same arguments as the standard list tasks command.

GET _cat/tasks
GET _cat/tasks?detailed

If a long-running task supports cancellation, it can be cancelled by the following command:

POST _tasks/node_id:task_id/_cancel

The task cancellation command supports the same task selection parameters as the list tasks command, so multiple tasks can be cancelled at the same time. For example, the following command will cancel all reindex tasks running on the nodes nodeId1 and nodeId2.

POST _tasks/_cancel?nodes=nodeId1,nodeId2&actions=*reindex

The task lists returned by task API commands can be grouped either by nodes (default) or by parent tasks using the group_by parameter. The following command will change the grouping to parent tasks:

GET _tasks?group_by=parents