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 org.apache.apex.examples.throttle;
  
  import java.util.Collection;
  
  import org.apache.hadoop.conf.Configuration;
  
  import com.google.common.collect.Lists;
  
  import com.datatorrent.api.Context;
  import com.datatorrent.api.DAG;
  import com.datatorrent.api.StatsListener;
  import com.datatorrent.api.StreamingApplication;
  import com.datatorrent.api.annotation.ApplicationAnnotation;
  
  @ApplicationAnnotation(name = "ThrottleApplication")
  /**
   * @since 3.7.0
   */
  public class Application implements StreamingApplication
  {
  
    @Override
    public void populateDAG(DAG dag, Configuration conf)
    {
      // Creating an example application with three operators
      // The last operator is slowing down the DAG
      // With the use of the stats listener the input operator is slowed when the window difference crosses a threshold
  
      RandomNumberGenerator randomGenerator = dag.addOperator("RandomGenerator", RandomNumberGenerator.class);
      PassThroughOperator<Double> passThrough = dag.addOperator("PassThrough", PassThroughOperator.class);
      SlowDevNullOperator<Double> devNull = dag.addOperator("SlowNull", SlowDevNullOperator.class);
  
      // Important to use the same stats listener object for all operators so that we can centrally collect stats and make
      // the decision
      StatsListener statsListener = new ThrottlingStatsListener();
      Collection<StatsListener> statsListeners = Lists.newArrayList(statsListener);
      dag.setAttribute(randomGenerator, Context.OperatorContext.STATS_LISTENERS, statsListeners);
      dag.setAttribute(passThrough, Context.OperatorContext.STATS_LISTENERS, statsListeners);
      dag.setAttribute(devNull, Context.OperatorContext.STATS_LISTENERS, statsListeners);
  
      // Increase timeout for the slow operator, this specifies the maximum timeout for an operator to process a window
      // It is specified in number of windows, since 1 window is 500ms, 30 minutes is 30 * 60 * 2 = 3600 windows
      dag.setAttribute(devNull, Context.OperatorContext.TIMEOUT_WINDOW_COUNT, 3600);
  
      // If there are unifiers that are slow then set timeout for them
      // dag.setUnifierAttribute(passThrough.output, Context.OperatorContext.TIMEOUT_WINDOW_COUNT, 3600);
  
      dag.addStream("randomData", randomGenerator.out, passThrough.input);
      dag.addStream("passData", passThrough.output, devNull.input);
    }
  }
  