examples/throttle/src/main/java/org/apache/apex/examples/throttle/ThrottlingStatsListener.java

/**
 * 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.io.IOException;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.Maps;

import com.datatorrent.api.Operator;
import com.datatorrent.api.StatsListener;

/**
 * Created by pramod on 9/27/16.
 *
 * @since 3.7.0
 */
public class ThrottlingStatsListener implements StatsListener, Serializable
{

  private static final Logger logger = LoggerFactory.getLogger(ThrottlingStatsListener.class);

  // Slowdown input if the window difference between operators increases beyond this value
  long maxThreshold = 100;
  // restore input operator to normal speed if the window difference falls below this threshold
  long minThreshold = 100;

  Map<Integer, ThrottleState> throttleStates = Maps.newHashMap();

  static class ThrottleState
  {
    // The current state of the operator, normal or throttled
    boolean normal = true;
    //The latest window id for which stats were received for the operator
    long currentWindowId;
  }

  // This method runs on the app master side and is called whenever new stats are received from the operators
  @Override
  public Response processStats(BatchedOperatorStats batchedOperatorStats)
  {
    Response response = new Response();
    int operatorId = batchedOperatorStats.getOperatorId();

    ThrottleState throttleState = throttleStates.get(operatorId);
    if (throttleState == null) {
      throttleState = new ThrottleState();
      throttleStates.put(operatorId, throttleState);
    }

    long windowId = batchedOperatorStats.getCurrentWindowId();
    throttleState.currentWindowId = windowId;

    // Find min and max window to compute difference
    long minWindow = Long.MAX_VALUE;
    long maxWindow = Long.MIN_VALUE;
    for (ThrottleState state : throttleStates.values()) {
      if (state.currentWindowId < minWindow) {
        minWindow = state.currentWindowId;
      }
      if (state.currentWindowId > maxWindow) {
        maxWindow = state.currentWindowId;
      }
    }
    logger.debug("Operator {} min window {} max window {}", operatorId, minWindow, maxWindow);

    if (throttleState.normal && ((maxWindow - minWindow) > maxThreshold)) {
      // Send request to operator to slow down
      logger.info("Sending suspend request");
      List<OperatorRequest> operatorRequests = new ArrayList<OperatorRequest>();
      operatorRequests.add(new InputSlowdownRequest());
      response.operatorRequests = operatorRequests;
      //logger.info("Setting suspend");
      throttleState.normal = false;
    } else if (!throttleState.normal && ((maxWindow - minWindow) <= minThreshold)) {
      // Send request to operator to get back to normal
      logger.info("Sending normal request");
      List<OperatorRequest> operatorRequests = new ArrayList<OperatorRequest>();
      operatorRequests.add(new InputNormalRequest());
      response.operatorRequests = operatorRequests;
      //logger.info("Setting normal");
      throttleState.normal = true;
    }

    return response;
  }

  // This runs on the operator side
  public static class InputSlowdownRequest implements OperatorRequest, Serializable
  {
    private static final Logger logger = LoggerFactory.getLogger(InputSlowdownRequest.class);

    @Override
    public OperatorResponse execute(Operator operator, int operatorId, long windowId) throws IOException
    {
      logger.debug("Received slowdown operator {} operatorId {} windowId {}", operator, operatorId, windowId);
      if (operator instanceof RandomNumberGenerator) {
        RandomNumberGenerator generator = (RandomNumberGenerator)operator;
        generator.suspend();
      }
      return new InputOperatorResponse();
    }
  }

  public static class InputNormalRequest implements OperatorRequest, Serializable
  {
    private static final Logger logger = LoggerFactory.getLogger(InputNormalRequest.class);

    @Override
    public OperatorResponse execute(Operator operator, int operatorId, long windowId) throws IOException
    {
      logger.debug("Received normal operator {} operatorId {} windowId {}", operator, operatorId, windowId);
      if (operator instanceof RandomNumberGenerator) {
        RandomNumberGenerator generator = (RandomNumberGenerator)operator;
        generator.normal();
      }
      return new InputOperatorResponse();
    }
  }

  public static class InputOperatorResponse implements OperatorResponse, Serializable
  {
    @Override
    public Object getResponseId()
    {
      return 1;
    }

    @Override
    public Object getResponse()
    {
      return "";
    }
  }

  public long getMaxThreshold()
  {
    return maxThreshold;
  }

  public void setMaxThreshold(long maxThreshold)
  {
    this.maxThreshold = maxThreshold;
  }

  public long getMinThreshold()
  {
    return minThreshold;
  }

  public void setMinThreshold(long minThreshold)
  {
    this.minThreshold = minThreshold;
  }
}