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;
  
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.ScheduledFuture;
  import java.util.concurrent.TimeUnit;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import backtype.storm.topology.FailedException;
  
  /**
   * Invokes {@link TriggerHandler#onTrigger()} after the duration.
   */
  public class TimeTriggerPolicy<T> implements TriggerPolicy<T> {
      private static final Logger LOG = LoggerFactory.getLogger(TimeTriggerPolicy.class);
  
      private long duration;
      private final TriggerHandler handler;
      private final ScheduledExecutorService executor;
      private final EvictionPolicy<T> evictionPolicy;
      private ScheduledFuture<?> executorFuture;
  
      public TimeTriggerPolicy(long millis, TriggerHandler handler) {
          this(millis, handler, null);
      }
  
      public TimeTriggerPolicy(long millis, TriggerHandler handler, EvictionPolicy<T> evictionPolicy) {
          this.duration = millis;
          this.handler = handler;
          this.executor = Executors.newSingleThreadScheduledExecutor();
          this.evictionPolicy = evictionPolicy;
      }
  
      @Override
      public void track(Event<T> event) {
          checkFailures();
      }
  
      @Override
      public void reset() {
          checkFailures();
      }
  
      @Override
      public void start() {
          executorFuture = executor.scheduleAtFixedRate(newTriggerTask(), duration, duration, TimeUnit.MILLISECONDS);
      }
  
      @Override
      public void shutdown() {
          executor.shutdown();
          try {
              if (!executor.awaitTermination(2, TimeUnit.SECONDS)) {
                  executor.shutdownNow();
              }
          } catch (InterruptedException ie) {
              executor.shutdownNow();
              Thread.currentThread().interrupt();
          }
      }
  
      @Override
      public String toString() {
          return "TimeTriggerPolicy{" +
                  "duration=" + duration +
                  '}';
      }
  
      /*
      * Check for uncaught exceptions during the execution
      * of the trigger and fail fast.
      * The uncaught exceptions will be wrapped in
      * ExecutionException and thrown when future.get() is invoked.
      */
      private void checkFailures() {
          if (executorFuture != null && executorFuture.isDone()) {
              try {
                  executorFuture.get();
              } catch (InterruptedException ex) {
                  LOG.error("Got exception ", ex);
                  throw new FailedException(ex);
              } catch (ExecutionException ex) {
                  LOG.error("Got exception ", ex);
                  throw new FailedException(ex.getCause());
              }
          }
      }
  
      private Runnable newTriggerTask() {
          return new Runnable() {
              @Override
              public void run() {
                  try {
                      /*
                       * set the current timestamp as the reference time for the eviction policy
                       * to evict the events
                       */
                      if (evictionPolicy != null) {
                          evictionPolicy.setContext(System.currentTimeMillis());
                      }
                      handler.onTrigger();
                  } catch (Throwable th) {
                      LOG.error("handler.onTrigger failed ", th);
                      /*
                       * propagate it so that task gets canceled and the exception
                       * can be retrieved from executorFuture.get()
                       */
                      throw th;
                  }
              }
          };
      }
  }
  