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Spring Retry provides an abstraction around retrying failed operations, with an emphasis on declarative control of the process and policy-based bahaviour that is easy to extend and customize. For instance, you can configure a plain POJO operation to retry if it fails, based on the type of exception, and with a fixed or exponential backoff.
/*
* Copyright 2006-2007 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 org.springframework.retry.support;
import java.util.ArrayList;
import java.util.List;
import org.springframework.retry.RetryCallback;
import org.springframework.retry.RetryContext;
import org.springframework.retry.RetryPolicy;
import org.springframework.retry.backoff.Sleeper;
import org.springframework.retry.backoff.SleepingBackOffPolicy;
/**
* A {@link RetrySimulator} is a tool for exercising retry + backoff operations.
*
* When calibrating a set of retry + backoff pairs, it is useful to know the behaviour
* of the retry for various scenarios.
*
* Things you may want to know:
* - Does a 'maxInterval' of 5000 ms in my backoff even matter?
* (This is often the case when retry counts are low -- so why set the max interval
* at something that cannot be achieved?)
* - What are the typical sleep durations for threads in a retry
* - What was the longest sleep duration for any retry sequence
*
* The simulator provides this information by executing a retry + backoff pair until failure
* (that is all retries are exhausted). The information about each retry is provided
* as part of the {@link RetrySimulation}.
*
* Note that the impetus for this class was to expose the timings which are possible with
* {@link org.springframework.retry.backoff.ExponentialRandomBackOffPolicy}, which provides
* random values and must be looked at over a series of trials.
*
* @author Jon Travis
*/
public class RetrySimulator {
private final SleepingBackOffPolicy backOffPolicy;
private final RetryPolicy retryPolicy;
public RetrySimulator(SleepingBackOffPolicy backOffPolicy, RetryPolicy retryPolicy) {
this.backOffPolicy = backOffPolicy;
this.retryPolicy = retryPolicy;
}
/**
* Execute the simulator for a give # of iterations.
*
* @param numSimulations Number of simulations to run
* @return the outcome of all simulations
*/
public RetrySimulation executeSimulation(int numSimulations) {
RetrySimulation simulation = new RetrySimulation();
for (int i=0; i executeSingleSimulation() {
StealingSleeper stealingSleeper = new StealingSleeper();
SleepingBackOffPolicy stealingBackoff = backOffPolicy.withSleeper(stealingSleeper);
RetryTemplate template = new RetryTemplate();
template.setBackOffPolicy(stealingBackoff);
template.setRetryPolicy(retryPolicy);
try {
template.execute(new FailingRetryCallback());
} catch(FailingRetryException e) {
} catch(Throwable e) {
throw new RuntimeException("Unexpected exception", e);
}
return stealingSleeper.getSleeps();
}
static class FailingRetryCallback implements RetryCallback