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/*
* Copyright 2006-2014 the original author or authors.
*
* Licensed 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 io.bitsensor.plugins.shaded.org.springframework.retry.backoff;
import io.bitsensor.plugins.shaded.org.apache.commons.logging.Log;
import io.bitsensor.plugins.shaded.org.apache.commons.logging.LogFactory;
import io.bitsensor.plugins.shaded.org.springframework.retry.RetryContext;
import io.bitsensor.plugins.shaded.org.springframework.util.ClassUtils;
/**
* Implementation of {@link BackOffPolicy} that increases the back off period for each
* retry attempt in a given set using the {@link Math#exp(double) exponential} function.
*
* This implementation is thread-safe and suitable for concurrent access. Modifications to
* the configuration do not affect any retry sets that are already in progress.
*
* The {@link #setInitialInterval(long)} property controls the initial value passed to
* {@link Math#exp(double)} and the {@link #setMultiplier(double)} property controls by
* how much this value is increased for each subsequent attempt.
*
* @author Rob Harrop
* @author Dave Syer
* @author Gary Russell
* @author Artem Bilan
*/
@SuppressWarnings("serial")
public class ExponentialBackOffPolicy
implements SleepingBackOffPolicy {
protected final Log logger = LogFactory.getLog(this.getClass());
/**
* The default 'initialInterval' value - 100 millisecs. Coupled with the default
* 'multiplier' value this gives a useful initial spread of pauses for 1-5 retries.
*/
public static final long DEFAULT_INITIAL_INTERVAL = 100L;
/**
* The default maximum backoff time (30 seconds).
*/
public static final long DEFAULT_MAX_INTERVAL = 30000L;
/**
* The default 'multiplier' value - value 2 (100% increase per backoff).
*/
public static final double DEFAULT_MULTIPLIER = 2;
/**
* The initial sleep interval.
*/
private volatile long initialInterval = DEFAULT_INITIAL_INTERVAL;
/**
* The maximum value of the backoff period in milliseconds.
*/
private volatile long maxInterval = DEFAULT_MAX_INTERVAL;
/**
* The value to increment the exp seed with for each retry attempt.
*/
private volatile double multiplier = DEFAULT_MULTIPLIER;
private Sleeper sleeper = new ThreadWaitSleeper();
/**
* Public setter for the {@link Sleeper} strategy.
* @param sleeper the sleeper to set defaults to {@link ThreadWaitSleeper}.
*/
public void setSleeper(Sleeper sleeper) {
this.sleeper = sleeper;
}
public ExponentialBackOffPolicy withSleeper(Sleeper sleeper) {
ExponentialBackOffPolicy res = newInstance();
cloneValues(res);
res.setSleeper(sleeper);
return res;
}
protected ExponentialBackOffPolicy newInstance() {
return new ExponentialBackOffPolicy();
}
protected void cloneValues(ExponentialBackOffPolicy target) {
target.setInitialInterval(getInitialInterval());
target.setMaxInterval(getMaxInterval());
target.setMultiplier(getMultiplier());
target.setSleeper(sleeper);
}
/**
* Set the initial sleep interval value. Default is {@code 100} millisecond. Cannot be
* set to a value less than one.
*
* @param initialInterval the initial interval
*/
public void setInitialInterval(long initialInterval) {
this.initialInterval = (initialInterval > 1 ? initialInterval : 1);
}
/**
* Set the multiplier value. Default is '2.0'. Hint: do not use values
* much in excess of 1.0 (or the backoff will get very long very fast).
* @param multiplier the multiplier
*/
public void setMultiplier(double multiplier) {
this.multiplier = (multiplier > 1.0 ? multiplier : 1.0);
}
/**
* Setter for maximum back off period. Default is 30000 (30 seconds). the value will
* be reset to 1 if this method is called with a value less than 1. Set this to avoid
* infinite waits if backing off a large number of times (or if the multiplier is set
* too high).
*
* @param maxInterval in milliseconds.
*/
public void setMaxInterval(long maxInterval) {
this.maxInterval = maxInterval > 0 ? maxInterval : 1;
}
/**
* The initial period to sleep on the first backoff.
* @return the initial interval
*/
public long getInitialInterval() {
return initialInterval;
}
/**
* The maximum interval to sleep for. Defaults to 30 seconds.
*
* @return the maximum interval.
*/
public long getMaxInterval() {
return maxInterval;
}
/**
* The multiplier to use to generate the next backoff interval from the last.
*
* @return the multiplier in use
*/
public double getMultiplier() {
return multiplier;
}
/**
* Returns a new instance of {@link BackOffContext} configured with the 'expSeed' and
* 'increment' values.
*/
public BackOffContext start(RetryContext context) {
return new ExponentialBackOffContext(this.initialInterval, this.multiplier,
this.maxInterval);
}
/**
* Pause for a length of time equal to ' exp(backOffContext.expSeed)'.
*/
public void backOff(BackOffContext backOffContext)
throws BackOffInterruptedException {
ExponentialBackOffContext context = (ExponentialBackOffContext) backOffContext;
try {
long sleepTime = context.getSleepAndIncrement();
if (logger.isDebugEnabled()) {
logger.debug("Sleeping for " + sleepTime);
}
sleeper.sleep(sleepTime);
}
catch (InterruptedException e) {
throw new BackOffInterruptedException("Thread interrupted while sleeping", e);
}
}
static class ExponentialBackOffContext implements BackOffContext {
private final double multiplier;
private long interval;
private long maxInterval;
public ExponentialBackOffContext(long expSeed, double multiplier,
long maxInterval) {
this.interval = expSeed;
this.multiplier = multiplier;
this.maxInterval = maxInterval;
}
public synchronized long getSleepAndIncrement() {
long sleep = this.interval;
if (sleep > maxInterval) {
sleep = maxInterval;
}
else {
this.interval = getNextInterval();
}
return sleep;
}
protected long getNextInterval() {
return (long) (this.interval * this.multiplier);
}
public double getMultiplier() {
return multiplier;
}
public long getInterval() {
return interval;
}
public long getMaxInterval() {
return maxInterval;
}
}
public String toString() {
return ClassUtils.getShortName(getClass()) + "[initialInterval=" + initialInterval
+ ", multiplier=" + multiplier + ", maxInterval=" + maxInterval + "]";
}
}