twentwo / spring-retry-showcase

spring-retry showcase

Spring retry基本使用

背景介绍

在实际工作过程中，重试是一个经常使用的手段。比如MQ发送消息失败，会采取重试手段，比如工程中使用RPC请求外部服务,可能因为网络 波动出现超时而采取重试手段......可以看见重试操作是非常常见的一种处理问题,系统设计的手段

而在之前我们项目中处理重拾操作依赖MQ自身的重试机制,但是这种机制不是很灵活,如果某些功能没有使用MQ的话,那么就不是那么方便了,而本文介绍的 Spring-Retry却能够以一种很优雅的方式解决这种问题,当然目前版本的Spring-retry还不是完美的,还是有待改进的.不过已经很不错了.

基本使用

• 例子1

    @Configuration
    @EnableRetry
    public class Application {
    
        @Bean
        public Service service() {
            return new Service();
        }
    
    }
    
    @Service
    class Service {
        @Retryable(RemoteAccessException.class)
        public void service() {
            // ... do something
        }
        @Recover
        public void recover(RemoteAccessException e) {
           // ... panic
        }
    }
  

• 例子2

   @org.springframework.stereotype.Service
   public class Service1 {
   
       @Retryable(value = {RemoteAccessException.class, RuntimeException.class},
               maxAttempts = 2,
               backoff = @Backoff(value = 2000))
       public void service() {
           System.out.println("do some things");
           // this exception will just trigger recover1, do not trigger recover3
           throw new RemoteAccessException("remote access exception");
           // this exception will just trigger recover2
   //        throw new RuntimeException("runtime exception");
   
   //        System.out.println("do another things");
       }
   
       // 如果使用注解的话,这个recover貌似只能写在本类中,我测试了如果将recover方法写在
       // recoverService中,好像找不到
   
       @Recover
       public void recover1(RemoteAccessException e) {
           System.out.println(e.getMessage());
           System.out.println("do recover operation1");
       }
   
       @Recover
       public void recover2(RuntimeException e) {
           System.out.println(e.getMessage());
           System.out.println("do recover operation2");
       }
   
       @Recover
       public void recover3(RemoteAccessException e) {
           System.out.println(e.getMessage());
           System.out.println("do recover operation3");
       }
   
   }
  

• 例子3

   @Service
   public class Service2 {
   
       public void test(){
           final RetryTemplate retryTemplate = new RetryTemplate();
           final SimpleRetryPolicy policy = new SimpleRetryPolicy(3, Collections.<Class<? extends Throwable>, Boolean>
                   singletonMap(Exception.class, true));
           FixedBackOffPolicy fixedBackOffPolicy = new FixedBackOffPolicy();
           fixedBackOffPolicy.setBackOffPeriod(100);
           retryTemplate.setRetryPolicy(policy);
           retryTemplate.setBackOffPolicy(fixedBackOffPolicy);
           final RetryCallback<Object, Exception> retryCallback = new RetryCallback<Object, Exception>() {
               public Object doWithRetry(RetryContext context) throws Exception {
                   System.out.println("do some thing");
                   //设置context一些属性,给RecoveryCallback传递一些属性
                   context.setAttribute("key1", "value1");
                   System.out.println(context.getRetryCount());
                   throw new Exception("exception");
   //                return null;
               }
           };
   
           // 如果RetryCallback执行出现指定异常, 并且超过最大重试次数依旧出现指定异常的话,就执行RecoveryCallback动作
           final RecoveryCallback<Object> recoveryCallback = new RecoveryCallback<Object>() {
               public Object recover(RetryContext context) throws Exception {
                   System.out.println("do recory operation");
                   System.out.println(context.getAttribute("key1"));
                   return null;
               }
           };
   
           try {
               final Object execute = retryTemplate.execute(retryCallback, recoveryCallback);
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }
  

参考资料

• spring-retry
• Spring retry – ways to integrate with your project