前言

        在微服务场景中,可能因为系统中网络抖动,导致调用超时或者失败, 按照我们分布式事务角度来看的话, 如果我们在业务中只调用了一次远程的服务查询(只去查询用户服务的某个信息),如果查询失败, 从而导致整个业务回滚, 这种代价是我们不想看到,所以我们就可以基于fegin的远程调用, 提高成功的可能性, 尽可能的避免回滚

来 我们上代码

        首先基于AOP注解的方式, 定义切面

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface FeignRetry {Backoff backoff() default @Backoff(); //定义重试机制int maxAttempt() default 3; //最大重试次数Class<? extends Throwable>[] include() default {} ;}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Backoff {long delay() default 1000L; //第一次重试时间间隔long maxDelay() default 0L; //最大延迟时间double multiplier() default 0.0D;}

 

@Aspect
@Slf4j
@Component
public class FeignRetryAspect {@Around("@annotation(com.yomahub.tlog.example.feign.inteferce.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));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());},context -> {//重试失败后执行的代码log.info("我在重试了{}次后，我最终还是失败了======", context.getRetryCount());return "failed callback";});}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();}

@FeignClient("tlog-logback-feign-provider")
public interface TLogFeignClient {@RequestMapping(value = "hi",method = RequestMethod.GET)@FeignRetry(maxAttempt = 6, backoff = @Backoff(delay = 500L, maxDelay = 20000L, multiplier = 4))public String sayHello(@RequestParam(value = "name") String name);}