content: /**
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package backtype.storm.windowing;
  
  /**
   * Triggers the window calculations based on the policy.
   *
   * @param <T> the type of the event that is tracked
   */
  public interface TriggerPolicy<T> {
      /**
       * Tracks the event and could use this to invoke the trigger.
       *
       * @param event the input event
       */
      void track(Event<T> event);
  
      /**
       * resets the trigger policy
       */
      void reset();
  
      /**
       * Starts the trigger policy. This can be used
       * during recovery to start the triggers after
       * recovery is complete.
       */
      void start();
  
      /**
       * Any clean up could be handled here.
       */
      void shutdown();
  }
  