如何实现指数延迟/睡眠以进行尝试和捕获

Question

我正在尝试编写另一个装饰器，如下面的RetriableProcessorDecorator （作为一个单独的类），以便它在重试时会出现指数延迟。 例如，如果消息无法处理，我们等待1秒钟（应可配置），然后等待2s，然后等待4s，然后等待8s，然后等待16s，依此类推。我想使用线程而不是忙等待，因为它比较便宜。 我写了一个新的RetriableProcessorExponentialDecorator类来做到这一点，但是我不确定这是否是正确的方法。

RetriableProcessorDecorator.java：

@Slf4j
@Setter
@RequiredArgsConstructor
@AllArgsConstructor(access = AccessLevel.PACKAGE)
public class RetriableProcessorDecorator implements.   
AbsMessageProcessorDecorator {
private final AbsMessageProcessor messageProcessor;
@Autowired
private AbsMessageActiveMQConfiguration configuration;

@Override
public void onMessage(AbsMessage message) throws Exception {
    int executionCounter = 0;
    final int maxRetries = this.configuration.getExceptionRetry() + 1;
    do {
        executionCounter++;
        try {
            this.messageProcessor.onMessage(message);
        } catch (RetriableException e) {
            log.info("Failed to process message. Retry #{}", executionCounter);
        } catch (Exception e) {
            // We don't retry on this, only RetriableException.
            throw e;
        }
    } while (executionCounter < maxRetries);
}
}

RetriableProcessorExponentialDecorator.java（我正在实现的新类）：

public class RetriableProcessorExponentialDecorator implements AbsMessageProcessorDecorator {
  private final AbsMessageProcessor messageProcessor;
  @Autowired
  private AbsMessageActiveMQConfiguration configuration;

  @Override
  public void onMessage(AbsMessage message) throws Exception {
    int executionCounter = 0;
    int delayCounter = 1000;
    final int maxRetries = this.configuration.getExceptionRetry() + 1;
    do {
      executionCounter++;
      try {
        this.messageProcessor.onMessage(message);
      } catch (RetriableException e) {
        log.info("Failed to process message. Retry #{}", executionCounter);
        Thread.sleep(delayCounter);
        delayCounter = delayCounter * 2;
      } catch (Exception e) {
        // We don't retry on this, only RetriableException.
        throw e;
      }
    } while (executionCounter < maxRetries && delayCounter < Long.MAX_VALUE);
  }
}

Answer 1

总的来说，我认为您的方法很好。

但是，如果您想使其可配置（即更有用），则可以执行以下操作：

double multiplier = 2.0; // make this configurable
...
delayCounter = (long) (delayCounter * (Math.pow(multiplier, executionCounter)));
Thread.sleep(delayCounter);

您还可以添加一种方法来配置最大延迟，这对于某些用例可能很方便，例如：

long maxDelay = 300000; // 5 minutes
...
if (delayCounter > maxDelay) {
   delayCounter = maxDelay;
}
Thread.sleep(delayCounter);