storm-client/src/jvm/org/apache/storm/utils/StormBoundedExponentialBackoffRetry.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.storm.utils;

import java.util.Random;
import org.apache.storm.shade.org.apache.curator.retry.BoundedExponentialBackoffRetry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class StormBoundedExponentialBackoffRetry extends BoundedExponentialBackoffRetry {
    private static final Logger LOG = LoggerFactory.getLogger(StormBoundedExponentialBackoffRetry.class);
    private final Random random = new Random();
    private final int linearBaseSleepMs;
    private final int stepSize;
    private int expRetriesThreshold;

    /**
     * The class provides generic exponential-linear backoff retry strategy for storm. It calculates threshold for exponentially increasing
     * sleeptime for retries. Beyond this threshold, the sleeptime increase is linear.
     *
     * <p>Also adds jitter for exponential/linear retry. It guarantees `currSleepTimeMs >= prevSleepTimeMs` and `baseSleepTimeMs <=
     * currSleepTimeMs <= maxSleepTimeMs`
     */
    public StormBoundedExponentialBackoffRetry(int baseSleepTimeMs, int maxSleepTimeMs, int maxRetries) {
        super(baseSleepTimeMs, maxSleepTimeMs, maxRetries);
        expRetriesThreshold = 1;
        while ((1 << (expRetriesThreshold + 1)) < ((maxSleepTimeMs - baseSleepTimeMs) / 2)) {
            expRetriesThreshold++;
        }
        LOG.debug("The baseSleepTimeMs [{}] the maxSleepTimeMs [{}] the maxRetries [{}]",
            baseSleepTimeMs, maxSleepTimeMs, maxRetries);
        if (baseSleepTimeMs > maxSleepTimeMs) {
            LOG.warn("Misconfiguration: the baseSleepTimeMs [" + baseSleepTimeMs + "] can't be greater than "
                + "the maxSleepTimeMs [" + maxSleepTimeMs + "].");
        }
        if (maxRetries > 0 && maxRetries > expRetriesThreshold) {
            this.stepSize = Math.max(1, (maxSleepTimeMs - (1 << expRetriesThreshold)) / (maxRetries - expRetriesThreshold));
        } else {
            this.stepSize = 1;
        }
        this.linearBaseSleepMs = super.getBaseSleepTimeMs() + (1 << expRetriesThreshold);
    }

    @Override
    public long getSleepTimeMs(int retryCount, long elapsedTimeMs) {
        if (retryCount < expRetriesThreshold) {
            int exp = 1 << retryCount;
            int jitter = random.nextInt(exp);
            long sleepTimeMs = super.getBaseSleepTimeMs() + exp + jitter;
            LOG.debug("WILL SLEEP FOR {}ms (NOT MAX)", sleepTimeMs);
            return sleepTimeMs;
        } else {
            int stepJitter = random.nextInt(stepSize);
            long sleepTimeMs = Math.min(super.getMaxSleepTimeMs(), (linearBaseSleepMs
                + (stepSize * (retryCount - expRetriesThreshold)) + stepJitter));
            LOG.debug("WILL SLEEP FOR {}ms (MAX)", sleepTimeMs);
            return sleepTimeMs;
        }
    }
}