content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.retry;
  
  import com.google.common.base.Preconditions;
  
  import java.util.concurrent.ThreadLocalRandom;
  import javax.annotation.concurrent.NotThreadSafe;
  
  /**
   * Each retry will cause a sleep to happen. This sleep will grow over time exponentially so each
   * sleep gets much larger than the last. To make sure that this growth does not grow out of control,
   * a max sleep is used as a bounding.
   */
  @NotThreadSafe
  public class ExponentialBackoffRetry extends SleepingRetry {
    private final int mBaseSleepTimeMs;
    private final int mMaxSleepMs;
  
    /**
     * Constructs a new retry facility which sleeps for an exponentially increasing amount of time
     * between retries.
     *
     * @param baseSleepTimeMs the sleep in milliseconds to begin with
     * @param maxSleepMs the max sleep in milliseconds as a bounding
     * @param maxRetries the max count of retries
     */
    public ExponentialBackoffRetry(int baseSleepTimeMs, int maxSleepMs, int maxRetries) {
      super(maxRetries);
      Preconditions.checkArgument(baseSleepTimeMs >= 0, "Base must be a positive number, or 0");
      Preconditions.checkArgument(maxSleepMs >= 0, "Max must be a positive number, or 0");
  
      mBaseSleepTimeMs = baseSleepTimeMs;
      mMaxSleepMs = maxSleepMs;
    }
  
    @Override
    protected long getSleepTime() {
      int count = getAttemptCount();
      if (count >= 30) {
        // current logic overflows at 30, so set value to max
        return mMaxSleepMs;
      } else {
        // use randomness to avoid contention between many operations using the same retry policy
        int sleepMs =
            mBaseSleepTimeMs * (ThreadLocalRandom.current().nextInt(1 << count, 1 << (count + 1)));
        return Math.min(Math.abs(sleepMs), mMaxSleepMs);
      }
    }
  
    @Override
    public ExponentialBackoffRetry copy() {
      return new ExponentialBackoffRetry(mBaseSleepTimeMs, mMaxSleepMs, mMaxRetries);
    }
  }
  