自定义注解@FeignRetry
为了解决上面提到的问题,让Feign调用的每个接口单独配置不同的重试机制。我们使用了面向切面编程并编写了一个自定义注解:@FeignRetry。此注释的工作方式类似于@Retryable的包装器,并与其共享相同的规范以避免混淆。
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface FeignRetry {Backoff backoff() default @Backoff();int maxAttempt() default 3;Class<? extends Throwable>[] include() default {};
}@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Backoff {long delay() default 1000L;;long maxDelay() default 0L;double multiplier() default 0.0D;;
}
FeignRetryAspect切面处理@FeignRetry注解。
Slf4j
@Aspect
@Component
public class FeignRetryAspect {@Around("@annotation(FeignRetry)")public Object retry(ProceedingJoinPoint joinPoint) throws Throwable {Method method = getCurrentMethod(joinPoint);FeignRetry feignRetry = method.getAnnotation(FeignRetry.class);RetryTemplate retryTemplate = new RetryTemplate();retryTemplate.setBackOffPolicy(prepareBackOffPolicy(feignRetry));retryTemplate.setRetryPolicy(prepareSimpleRetryPolicy(feignRetry));// 重试,注意这里execute还有第二个参数,可以设置重试全部失败以后的回调函数,再重试任然失败以后,可以编写回调函数来兜底return retryTemplate.execute(arg0 -> {int retryCount = arg0.getRetryCount();log.info("Sending request method: {}, max attempt: {}, delay: {}, retryCount: {}",method.getName(),feignRetry.maxAttempt(),feignRetry.backoff().delay(),retryCount);return joinPoint.proceed(joinPoint.getArgs());});}private BackOffPolicy prepareBackOffPolicy(FeignRetry feignRetry) {if (feignRetry.backoff().multiplier() != 0) {ExponentialBackOffPolicy backOffPolicy = new ExponentialBackOffPolicy();backOffPolicy.setInitialInterval(feignRetry.backoff().delay());backOffPolicy.setMaxInterval(feignRetry.backoff().maxDelay());backOffPolicy.setMultiplier(feignRetry.backoff().multiplier());return backOffPolicy;} else {FixedBackOffPolicy fixedBackOffPolicy = new FixedBackOffPolicy();fixedBackOffPolicy.setBackOffPeriod(feignRetry.backoff().delay());return fixedBackOffPolicy;}}private SimpleRetryPolicy prepareSimpleRetryPolicy(FeignRetry feignRetry) {Map<Class<? extends Throwable>, Boolean> policyMap = new HashMap<>();policyMap.put(RetryableException.class, true); // Connection refused or time outpolicyMap.put(ClientException.class, true); // Load balance does not available (cause of RunTimeException)if (feignRetry.include().length != 0) {for (Class<? extends Throwable> t : feignRetry.include()) {policyMap.put(t, true);}}return new SimpleRetryPolicy(feignRetry.maxAttempt(), policyMap, true);}private Method getCurrentMethod(JoinPoint joinPoint) {MethodSignature signature = (MethodSignature) joinPoint.getSignature();return signature.getMethod();}
}
捕获FeignRetry注解的方法,将配置传递给Spring RetryTemplate,根据配置调用服务。
@FeignRetry 的使用
用法很简单,只需将注释放在我们希望重试机制处于活动状态的 Feign Client方法上即可。自定义切面的用法类似于Spring自带的@Retryable注解。
@GetMapping
@FeignRetry(maxAttempt = 3, backoff = @Backoff(delay = 500L))
ResponseEntity<String> retrieve1();@GetMapping
@FeignRetry(maxAttempt = 6, backoff = @Backoff(delay = 500L, maxDelay = 20000L, multiplier = 4))
ResponseEntity<String> retrieve2();
另外还需要在应用程序类中使用 @EnableRetry 注释来启动重试,直接写在SpringBoot的启动类上。
这里再讲解一下,各个参数的含义
include:就是value,默认为空,当exclude也为空时,默认所有异常都可以触发重试
exclude:指定那些异常不触发重试(可以配置多个异常类型),默认为空
maxAttempts:最大重试次数,默认3次(包括第一次调用)
backoff:重试等待策略 默认使用@Backoff注解
@BackOff各个参数的讲解
value: 重试的间隔时间默认为1000L,我们设置为2000L
delay:重试的间隔时间,就是value
maxDelay:重试次数之间的最大时间间隔,默认为0,如果小于delay的设置,则默认为30000L
multiplier:delay时间的间隔倍数,默认为0,表示固定暂停1秒后进行重试,如果把multiplier设置为1.5,则第一次重试为2秒,第二次为3秒,第三次为4.5秒。