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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 2012-2015 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.stats;
/**
* @author Dave Syer
*
*/
@SuppressWarnings("serial")
public class ExponentialAverageRetryStatistics extends DefaultRetryStatistics {
private long window = 15000;
private ExponentialAverage started;
private ExponentialAverage error;
private ExponentialAverage complete;
private ExponentialAverage recovery;
private ExponentialAverage abort;
public ExponentialAverageRetryStatistics(String name) {
super(name);
init();
}
private void init() {
started = new ExponentialAverage(window);
error = new ExponentialAverage(window);
complete = new ExponentialAverage(window);
abort = new ExponentialAverage(window);
recovery = new ExponentialAverage(window);
}
/**
* Window in milliseconds for exponential decay factor in rolling average.
*
* @param window the window to set
*/
public void setWindow(long window) {
this.window = window;
init();
}
public int getRollingStartedCount() {
return (int) Math.round(started.getValue());
}
public int getRollingErrorCount() {
return (int) Math.round(error.getValue());
}
public int getRollingAbortCount() {
return (int) Math.round(abort.getValue());
}
public int getRollingRecoveryCount() {
return (int) Math.round(recovery.getValue());
}
public int getRollingCompleteCount() {
return (int) Math.round(complete.getValue());
}
public double getRollingErrorRate() {
if (Math.round(started.getValue())==0) {
return 0.;
}
return (abort.getValue() + recovery.getValue()) / started.getValue();
}
@Override
public void incrementStartedCount() {
super.incrementStartedCount();
started.increment();
}
@Override
public void incrementCompleteCount() {
super.incrementCompleteCount();
complete.increment();
}
@Override
public void incrementRecoveryCount() {
super.incrementRecoveryCount();
recovery.increment();
}
@Override
public void incrementErrorCount() {
super.incrementErrorCount();
error.increment();
}
@Override
public void incrementAbortCount() {
super.incrementAbortCount();
abort.increment();
}
private class ExponentialAverage {
private final double alpha;
private volatile long lastTime = System.currentTimeMillis();
private volatile double value = 0;
public ExponentialAverage(long window) {
alpha = 1. / window;
}
public synchronized void increment() {
long time = System.currentTimeMillis();
value = value * Math.exp(-alpha*(time - lastTime)) + 1;
lastTime = time;
}
public double getValue() {
long time = System.currentTimeMillis();
return value * Math.exp(-alpha*(time - lastTime));
}
}
}