org.apache.kafka.common.utils.ExponentialBackoff Maven / Gradle / Ivy
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* 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,
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* See the License for the specific language governing permissions and
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*/
package org.apache.kafka.common.utils;
import java.util.concurrent.ThreadLocalRandom;
/**
* A utility class for keeping the parameters and providing the value of exponential
* retry backoff, exponential reconnect backoff, exponential timeout, etc.
*
* The formula is:
*
Backoff(attempts) = random(1 - jitter, 1 + jitter) * initialInterval * multiplier ^ attempts
* If {@code initialInterval} is greater than or equal to {@code maxInterval}, a constant backoff of
* {@code initialInterval} will be provided.
*
* This class is thread-safe.
*/
public class ExponentialBackoff {
private final int multiplier;
private final double expMax;
private final long initialInterval;
private final double jitter;
public ExponentialBackoff(long initialInterval, int multiplier, long maxInterval, double jitter) {
this.initialInterval = initialInterval;
this.multiplier = multiplier;
this.jitter = jitter;
this.expMax = maxInterval > initialInterval ?
Math.log(maxInterval / (double) Math.max(initialInterval, 1)) / Math.log(multiplier) : 0;
}
public long backoff(long attempts) {
if (expMax == 0) {
return initialInterval;
}
double exp = Math.min(attempts, this.expMax);
double term = initialInterval * Math.pow(multiplier, exp);
double randomFactor = jitter < Double.MIN_NORMAL ? 1.0 :
ThreadLocalRandom.current().nextDouble(1 - jitter, 1 + jitter);
return (long) (randomFactor * term);
}
}