[[api-rest-ack-watch]]
==== Ack Watch API

<<actions-ack-throttle, Acknowledging>> a watch enables you to manually throttle
execution of the watch's actions. An action's _acknowledgement state_ is stored in the 
`_status.actions.<id>.ack.state` structure.

The current status of a watch and the state of its actions is returned with the watch
definition when you call the <<api-rest-get-watch, Get Watch API>>:

[source,json]
--------------------------------------------------
GET _watcher/watch/<watch_id>
--------------------------------------------------
// AUTOSENSE

The action state of a newly-created watch is `awaits_successful_execution`.

[source,js]
--------------------------------------------------
"_status": {
   ...
   "actions": {
    "action_id": {
     "ack": {
      "timestamp": "2015-05-26T18:04:27.723Z",
      "state": "awaits_successful_execution"
     },
     ...
    }
   }
}
--------------------------------------------------

When the watch runs and the condition matches, the value of the `ack.state` changes
to `ackable`:

[source,js]
--------------------------------------------------
"_status": {
   ...
   "actions": {
    "action_id": {
     "ack": {
      "timestamp": "2015-05-26T18:19:08.758Z",
      "state": "ackable"
     },
     ...
    }
   }
}
--------------------------------------------------

Acknowledging the watch action (using the ACK API) sets the value of the `ack.state`
to `acked`:

[source,js]
--------------------------------------------------
"_status": {
   ...
   "actions": {
    "action_id": {
     "ack": {
      "timestamp": "2015-05-26T18:21:09.982Z",
      "state": "acked"
     },
     ...
    }
   }
}
--------------------------------------------------

Acknowledging an action throttles further executions of that action until its 
`ack.state` is reset to `awaits_successful_execution`. This happens when the watch's condition
is checked and is not met (the condition evaluates to `false`).

The following snippet shows how to ack a watch action identified by its id. In this example, the
watch id is `my-watch` and the id of the action being acknowledged is `my-action`:

[source,js]
--------------------------------------------------
PUT _watcher/watch/my-watch/my-action/_ack
--------------------------------------------------
// AUTOSENSE

As a response to this request, the full watch status is returned:

[source,js]
--------------------------------------------------
{
   "_status": {
      "last_checked": "2015-05-26T18:21:08.630Z",
      "last_met_condition": "2015-05-26T18:21:08.630Z",
      "actions": {
         "my-action": {
            "ack_status": {
               "timestamp": "2015-05-26T18:21:09.982Z",
               "state": "acked"
            },
            "last_execution": {
               "timestamp": "2015-05-26T18:21:04.106Z",
               "successful": true
            },
            "last_successful_execution": {
               "timestamp": "2015-05-26T18:21:04.106Z",
               "successful": true
            },
            "last_throttle": {
               "timestamp": "2015-05-26T18:21:08.630Z",
               "reason": "throttling interval is set to [5 seconds] but time elapsed since last execution is [4 seconds and 530 milliseconds]"
            }
         }
      }
   }
}
--------------------------------------------------

You can acknowledge multiple actions by assigning the `actions` parameter a 
comma-separated list of action ids:

[source,js]
--------------------------------------------------
PUT _watcher/watch/my-watch/action1,action2/_ack
--------------------------------------------------
// AUTOSENSE

To acknowledge all of a watch's actions, simply omit the `actions` parameter:

[source,js]
--------------------------------------------------
PUT _watcher/watch/my-watch/_ack
--------------------------------------------------
// AUTOSENSE

===== Timeouts

If you acknowledge a watch while it is executing, the ack action blocks and waits for the watch
execution to finish. For some watches, this can take a significant amount of time. By default,
the ack watch action has a timeout of 10 seconds. You can change the timeout setting by
specifying the `master_timeout` parameter.

The following snippet shows how to change the default timeout of the ack action to 30 seconds:

[source,js]
--------------------------------------------------
PUT _watcher/watch/my-watch/_ack?master_timeout=30s
--------------------------------------------------
// AUTOSENSE