com.amazonaws.services.simpleworkflow.flow.worker.BackoffThrottler Maven / Gradle / Ivy

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The Amazon Web Services SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2012-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 com.amazonaws.services.simpleworkflow.flow.worker;

import java.util.concurrent.atomic.AtomicLong;

/**
 * Used to throttle code execution in presence of failures using exponential
 * backoff logic. The formula used to calculate the next sleep interval is:
 * 
 *  * min(pow(backoffCoefficient, failureCount - 1) * initialSleep, maxSleep);
 * 
 * 
 * Example usage:
 * 
 * 
 * BackoffThrottler throttler = new BackoffThrottler(1000, 60000, 2);
 * while(!stopped) {
 *     try {
 *         throttler.throttle();
 *         // some code that can fail and should be throttled
 *         ...
 *         throttler.success();
 *     }
 *     catch (Exception e) {
 *         throttler.failure();
 *     }
 * }
 * 
 * 
 * @author fateev
 */
public class BackoffThrottler {

    private final long initialSleep;

    private final long maxSleep;

    private final double backoffCoefficient;

    private final AtomicLong failureCount = new AtomicLong();

    /**
     * Construct an instance of the throttler.
     * 
     * @param initialSleep
     *            time to sleep on the first failure
     * @param maxSleep
     *            maximum time to sleep independently of number of failures
     * @param backoffCoefficient
     *            coefficient used to calculate the next time to sleep.
     */
    public BackoffThrottler(long initialSleep, long maxSleep, double backoffCoefficient) {
        this.initialSleep = initialSleep;
        this.maxSleep = maxSleep;
        this.backoffCoefficient = backoffCoefficient;
    }

    private long calculateSleepTime() {
        double sleepMillis = (Math.pow(backoffCoefficient, failureCount.get() - 1)) * initialSleep;
        return Math.min((long) sleepMillis, maxSleep);
    }

    /**
     * Sleep if there were failures since the last success call.
     * 
     * @throws InterruptedException
     */
    public void throttle() throws InterruptedException {
        if (failureCount.get() > 0) {
            Thread.sleep(calculateSleepTime());
        }
    }

    /**
     * Resent failure count to 0.
     */
    public void success() {
        failureCount.set(0);
    }

    /**
     * Increment failure count.
     */
    public void failure() {
        failureCount.incrementAndGet();
    }

}