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;
  
  /**
   * An eviction policy that tracks count based on watermark ts and
   * evicts events upto the watermark based on a threshold count.
   *
   * @param <T> the type of event tracked by this policy.
   */
  public class WatermarkCountEvictionPolicy<T> extends CountEvictionPolicy<T> {
      private final WindowManager<T> windowManager;
      /*
       * The reference time in millis for window calculations and
       * expiring events. If not set it will default to System.currentTimeMillis()
       */
      private long referenceTime;
  
      public WatermarkCountEvictionPolicy(int count, WindowManager<T> windowManager) {
          super(count);
          this.windowManager = windowManager;
      }
  
      @Override
      public Action evict(Event<T> event) {
          if (event.getTimestamp() <= referenceTime) {
              return super.evict(event);
          } else {
              return Action.KEEP;
          }
      }
  
      @Override
      public void track(Event<T> event) {
          // NOOP
      }
  
      @Override
      public void setContext(Object context) {
          referenceTime = (Long) context;
          currentCount.set(windowManager.getEventCount(referenceTime));
      }
  
      @Override
      public String toString() {
          return "WatermarkCountEvictionPolicy{" +
                  "referenceTime=" + referenceTime +
                  "} " + super.toString();
      }
  }
  