Package org.apache.storm.windowing

## Interface TriggerPolicy<T,​S>

- Type Parameters:
    `T` - the type of the event that is tracked
  All Known Implementing Classes:
    `CountTriggerPolicy`, `TimeTriggerPolicy`, `WatermarkCountTriggerPolicy`, `WatermarkTimeTriggerPolicy`

      public interface TriggerPolicy<T,​S>

  Triggers the window calculations based on the policy.

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `S` | `getState()` | Return runtime state to be checkpointed by the framework for restoring the trigger policy in case of failures.
    `void` | `reset()` | resets the trigger policy.
    `void` | `restoreState​(S state)` | Restore the trigger policy from the state that was earlier checkpointed by the framework.
    `void` | `shutdown()` | Any clean up could be handled here.
    `void` | `start()` | Starts the trigger policy.
    `void` | `track​(Event<T> event)` | Tracks the event and could use this to invoke the trigger.

- - ### Method Detail

    - #### track

          void track​(Event<T> event)

      Tracks the event and could use this to invoke the trigger.
      Parameters:
        `event` - the input event

    - #### reset

          void reset()

      resets the trigger policy.

    - #### start

          void start()

      Starts the trigger policy. This can be used during recovery to start the triggers after recovery is complete.

    - #### shutdown

          void shutdown()

      Any clean up could be handled here.

    - #### getState

          S getState()

      Return runtime state to be checkpointed by the framework for restoring the trigger policy in case of failures.
      Returns:
        the state

    - #### restoreState

          void restoreState​(S state)

      Restore the trigger policy from the state that was earlier checkpointed by the framework.
      Parameters:
        `state` - the state