ExponentialBackoffMsgRetryManager.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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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.storm.kafka;

import java.util.Comparator;
import java.util.HashSet;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

public class ExponentialBackoffMsgRetryManager implements FailedMsgRetryManager {

  private static final long serialVersionUID = 2345275003041762252L;
  private long retryInitialDelayMs;
  private double retryDelayMultiplier;
  private long retryDelayMaxMs;
  private int retryLimit;

  private Queue<MessageRetryRecord> waiting;
  private Map<Long, MessageRetryRecord> records;

  public ExponentialBackoffMsgRetryManager() {

  }

  public void prepare(SpoutConfig spoutConfig, Map<String, Object> stormConf) {
    this.retryInitialDelayMs = spoutConfig.retryInitialDelayMs;
    this.retryDelayMultiplier = spoutConfig.retryDelayMultiplier;
    this.retryDelayMaxMs = spoutConfig.retryDelayMaxMs;
    this.retryLimit = spoutConfig.retryLimit;
    this.waiting = new PriorityQueue<MessageRetryRecord>(11, new RetryTimeComparator());
    this.records = new ConcurrentHashMap<Long, MessageRetryRecord>();
  }

  @Override
  public void failed(Long offset) {
    MessageRetryRecord oldRecord = this.records.get(offset);
    MessageRetryRecord newRecord =
        oldRecord == null ? new MessageRetryRecord(offset) : oldRecord.createNextRetryRecord();
    this.records.put(offset, newRecord);
    this.waiting.add(newRecord);
  }

  @Override
  public void acked(Long offset) {
    MessageRetryRecord record = this.records.remove(offset);
    if (record != null) {
      this.waiting.remove(record);
    }
  }

  @Override
  public void retryStarted(Long offset) {
    MessageRetryRecord record = this.records.get(offset);
    if (record == null || !this.waiting.contains(record)) {
      throw new IllegalStateException("cannot retry a message that has not failed");
    } else {
      this.waiting.remove(record);
    }
  }

  @Override
  public Long nextFailedMessageToRetry() {
    if (this.waiting.size() > 0) {
      MessageRetryRecord first = this.waiting.peek();
      if (System.currentTimeMillis() >= first.retryTimeUTC) {
        if (this.records.containsKey(first.offset)) {
          return first.offset;
        } else {
          // defensive programming - should be impossible
          this.waiting.remove(first);
          return nextFailedMessageToRetry();
        }
      }
    }
    return null;
  }

  @Override
  public boolean shouldReEmitMsg(Long offset) {
    MessageRetryRecord record = this.records.get(offset);
    return record != null
        && this.waiting.contains(record)
        && System.currentTimeMillis() >= record.retryTimeUTC;
  }

  @Override
  public boolean retryFurther(Long offset) {
    MessageRetryRecord record = this.records.get(offset);
    return !(record != null && this.retryLimit > 0 && this.retryLimit <= record.retryNum);
  }

  @Override
  public Set<Long> clearOffsetsBefore(Long kafkaOffset) {
    Set<Long> invalidOffsets = new HashSet<Long>();
    for (Long offset : records.keySet()) {
      if (offset < kafkaOffset) {
        MessageRetryRecord record = this.records.remove(offset);
        if (record != null) {
          this.waiting.remove(record);
          invalidOffsets.add(offset);
        }
      }
    }
    return invalidOffsets;
  }

  /**
   * A MessageRetryRecord holds the data of how many times a message has
   * failed and been retried, and when the last failure occurred.  It can
   * determine whether it is ready to be retried by employing an exponential
   * back-off calculation using config values stored in SpoutConfig:
   * <ul>
   *  <li>retryInitialDelayMs - time to delay before the first retry</li>
   *  <li>retryDelayMultiplier - multiplier by which to increase the delay for each subsequent
   *                             retry
   *  </li>
   *  <li>retryDelayMaxMs - maximum retry delay (once this delay time is reached, subsequent retries
   *                        will delay for this amount of time every time)
   *  </li>
   * </ul>
   */
  private class MessageRetryRecord {
    private final long offset;
    private final int retryNum;
    private final long retryTimeUTC;

    MessageRetryRecord(long offset) {
      this(offset, 1);
    }

    private MessageRetryRecord(long offset, int retryNum) {
      this.offset = offset;
      this.retryNum = retryNum;
      this.retryTimeUTC = System.currentTimeMillis() + calculateRetryDelay();
    }

    /**
     * Create a MessageRetryRecord for the next retry that should occur after this one.
     * @return MessageRetryRecord with the next retry time, or null to indicate that another
     *         retry should not be performed.  The latter case can happen if we are about to
     *         run into the org.apache.storm.Config.TOPOLOGY_MESSAGE_TIMEOUT_SECS in the Storm
     *         configuration.
     */
    public MessageRetryRecord createNextRetryRecord() {
      return new MessageRetryRecord(this.offset, this.retryNum + 1);
    }

    private long calculateRetryDelay() {
      double delayMultiplier = Math.pow(retryDelayMultiplier, this.retryNum - 1);
      double delay = retryInitialDelayMs * delayMultiplier;
      Long maxLong = Long.MAX_VALUE;
      long delayThisRetryMs = delay >= maxLong.doubleValue()
          ? maxLong
          : (long) delay;
      return Math.min(delayThisRetryMs, retryDelayMaxMs);
    }

    @Override
    public boolean equals(Object other) {
      return other instanceof MessageRetryRecord
          && this.offset == ((MessageRetryRecord) other).offset;
    }

    @Override
    public int hashCode() {
      return Long.valueOf(this.offset).hashCode();
    }
  }

  private static class RetryTimeComparator implements Comparator<MessageRetryRecord> {

    @Override
    public int compare(MessageRetryRecord record1, MessageRetryRecord record2) {
      return Long.valueOf(record1.retryTimeUTC).compareTo(Long.valueOf(record2.retryTimeUTC));
    }
  }
}