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;
  
  /**
   * Eviction policy that evicts events based on time duration.
   */
  public class TimeEvictionPolicy<T> implements EvictionPolicy<T> {
      private final int windowLength;
      /**
       * The reference time in millis for window calculations and
       * expiring events. If not set it will default to System.currentTimeMillis()
       */
      protected Long referenceTime;
  
      /**
       * Constructs a TimeEvictionPolicy that evicts events older
       * than the given window length in millis
       *
       * @param windowLength the duration in milliseconds
       */
      public TimeEvictionPolicy(int windowLength) {
          this.windowLength = windowLength;
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public Action evict(Event<T> event) {
          long now = referenceTime == null ? System.currentTimeMillis() : referenceTime;
          long diff = now - event.getTimestamp();
          if (diff >= windowLength) {
              return Action.EXPIRE;
          }
          return Action.PROCESS;
      }
  
      @Override
      public void track(Event<T> event) {
          // NOOP
      }
  
      @Override
      public void setContext(Object context) {
          referenceTime = ((Number) context).longValue();
      }
  
      @Override
      public String toString() {
          return "TimeEvictionPolicy{" +
                  "windowLength=" + windowLength +
                  ", referenceTime=" + referenceTime +
                  '}';
      }
  }
  