heron/api/src/java/com/twitter/heron/api/windowing/WindowLifecycleListener.java

//  Copyright 2017 Twitter. All rights reserved.
//
//  Licensed 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 com.twitter.heron.api.windowing;

import java.util.List;

/**
 * A callback for expiry, activation of events tracked by the {@link WindowManager}
 *
 * @param <T> The type of Event in the window (e.g. Tuple).
 */
public interface WindowLifecycleListener<T> {
  /**
   * Called on expiry of events from the window due to {@link EvictionPolicy}
   *
   * @param events the expired events
   */
  void onExpiry(List<T> events);

  /**
   * Called on activation of the window due to the {@link TriggerPolicy}
   *
   * @param events the list of current events in the window.
   * @param newEvents the newly added events since last activation.
   * @param expired the expired events since last activation.
   * @param referenceTime the reference (event or processing) time that resulted in activation
   */
  default void onActivation(List<T> events, List<T> newEvents, List<T> expired, Long
      referenceTime) {
    throw new UnsupportedOperationException("Not implemented");
  }
}