使用MongoDB进行乐观锁定重试

在我以前的文章中，我谈到了对MongoDB批处理程序采用乐观锁定的好处。如我之前所写，乐观锁异常是可恢复的异常，只要我们获取最新的Entity，我们就会对其进行更新并保存。

因为我们使用的是MongoDB，所以我们不必担心本地或XA事务。在以后的文章中，我将演示如何使用JPA构建相同的机制。

Spring框架提供了很好的AOP支持，因此可以轻松实现自动重试机制，这就是我的方法。

我们首先定义一个Retry注释：

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Retry {Class<? extends Exception>[] on();int times() default 1;
}

我们注释了我们的业务逻辑方法，例如

@Retry(times = 10, on = org.springframework.dao.OptimisticLockingFailureException.class)
public Product updateName(Long id, String name) {Product product = productRepository.findOne(id);product.setName(name);LOGGER.info("Updating product {} name to {}", product, name);return productRepository.save(product);
}

然后，我们只需要AOP方面来拦截业务逻辑调用，并在乐观锁定检测的情况下重试。

@Aspect
public class OptimisticConcurrencyControlAspect {private static final Logger LOGGER = LoggerFactory.getLogger(OptimisticConcurrencyControlAspect.class);@Around("@annotation(vladmihalcea.concurrent.Retry)")public Object retry(ProceedingJoinPoint pjp) throws Throwable {Retry retryAnnotation = getRetryAnnotation(pjp);return (retryAnnotation != null) ? proceed(pjp, retryAnnotation) : proceed(pjp);}private Object proceed(ProceedingJoinPoint pjp) throws Throwable {return pjp.proceed();}private Object proceed(ProceedingJoinPoint pjp, Retry retryAnnotation) throws Throwable {int times = retryAnnotation.times();Class<? extends Throwable>[] retryOn = retryAnnotation.on();Assert.isTrue(times > 0, "@Retry{times} should be greater than 0!");Assert.isTrue(retryOn.length > 0, "@Retry{on} should have at least one Throwable!");LOGGER.info("Proceed with {} retries on {}", times, Arrays.toString(retryOn));return tryProceeding(pjp, times, retryOn);}private Object tryProceeding(ProceedingJoinPoint pjp, int times, Class<? extends Throwable>[] retryOn) throws Throwable {try {return proceed(pjp);} catch (Throwable throwable) {if(isRetryThrowable(throwable, retryOn) && times-- > 0) {LOGGER.info("Optimistic locking detected, {} remaining retries on {}", times, Arrays.toString(retryOn));return tryProceeding(pjp, times, retryOn);}throw throwable;}}private boolean isRetryThrowable(Throwable throwable, Class<? extends Throwable>[] retryOn) {Throwable[] causes = ExceptionUtils.getThrowables(throwable);for(Throwable cause : causes) {for(Class<? extends Throwable> retryThrowable : retryOn) {if(retryThrowable.isAssignableFrom(cause.getClass())) {return true;}}}return false;}private Retry getRetryAnnotation(ProceedingJoinPoint pjp) throws NoSuchMethodException {MethodSignature signature = (MethodSignature) pjp.getSignature();Method method = signature.getMethod();Retry retryAnnotation = AnnotationUtils.findAnnotation(method, Retry.class);if(retryAnnotation != null) {return retryAnnotation;}Class[] argClasses = new Class[pjp.getArgs().length];for (int i = 0; i < pjp.getArgs().length; i++) {argClasses[i] = pjp.getArgs()[i].getClass();}method = pjp.getTarget().getClass().getMethod(pjp.getSignature().getName(), argClasses);return AnnotationUtils.findAnnotation(method, Retry.class);}
}

测试开始了10个竞标以竞争产品的保存，这就是测试日志。

Line 492: INFO  [Thread-9]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 9 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 495: INFO  [Thread-3]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 9 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 504: INFO  [Thread-8]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 9 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 505: INFO  [Thread-11]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 9 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 507: INFO  [Thread-10]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 9 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 513: INFO  [Thread-5]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 9 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 523: INFO  [Thread-4]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 9 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 529: INFO  [Thread-3]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 8 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 586: INFO  [Thread-10]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 8 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 682: INFO  [Thread-5]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 8 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 683: INFO  [Thread-3]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 7 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 686: INFO  [Thread-8]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 8 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 702: INFO  [Thread-3]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 6 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 752: INFO  [Thread-5]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 7 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 756: INFO  [Thread-8]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 7 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]Line 859: INFO  [Thread-5]: v.c.a.OptimisticConcurrencyControlAspect - Optimistic locking detected, 6 remaining retries on [class org.springframework.dao.OptimisticLockingFailureException]