[GitHub] rangtao opened a new issue #2525: Problems of graceful shutdown of dubbo in 2.6.3 and some recommendations

[GitBox <gi...@apache.org>]

rangtao opened a new issue #2525:  Problems of graceful shutdown of dubbo in 2.6.3 and some  recommendations
URL: https://github.com/apache/incubator-dubbo/issues/2525
 
 
   -关于2.6.3release版本优雅停机问题，之前我在社区也发提出的issue中于开发交流过，发现依然存在问题。
   1. 框架的停机hook和spring的停机hook同时触发，导致服务的实现类中无法获取业务bean，导致服务无法正确完成。（因为spring context先于框架close了）
   场景一：Springboot+innerTomcat
   @SpringBootApplication
   @ComponetScan
   @ImportResource({"classpath:/META-INF/spring/dubbo*.xml"})
   public class GatewayApplication {
   	public static void main(String[] args) {
   		SpringApplication.run(GatewayApplication.class, args);
   		System.in.read();
   		//模拟停机
   		System.exit(0);
   	}
   }
   场景二：
   public static void main(String[] args) {
   	ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext(classpath:/META-INF/spring/dubbo*.xml);
   	ctx.registerShutdownHook();
   	ctx.start();
   }
   
   2. 我们分析了下2.6.3停机代码，针对spring容器需要关闭dubbo默认hook，通过spring的停机hook触发close事件listener来停机。初始化DubboApplicationListener目前只针对Main方法和Spring+web.xml方式。个人觉得DubboApplicationListener思路是对的，但是需要针对不同spring使用场景，不能总体覆盖。个人觉得DubboApplicationContextInitializer设计就有点别扭。
   
   3. 建议：针对Spring容器优雅停机，我们建议将spring close事件监听逻辑移到ApplicationConfig中，并在ApplicationConfig中注销默认停机hook，注册spring 停机hook。这样做的好处就是，如果框架是基于spring容器，可以一刀切的方式实现hook的管理，完全依赖spirng管理停机，使用者仅需要关系spring生命周期。核心修改如下：
   ApplicationConfig implments ApplicationContextWare, ApplicationListener<ContextClosedEvent>{
       public void onApplicationEvent(ContextClosedEvent event){
           DubboShutdownHook.getDubboShutDownHook().destroyAll();
       }
   
       public void setApplicationContext(ApplicationContext ctx){
           //注销dubbohook，将removeShutdownHook从DubboBootstrap中迁移到DubboShutdownHook中
           DubboShutdownHook.removeShutdownHook();
          //注册spring hook
            ctx.registerShutdownHook();
       }
   }
   
   4.我们应用在实际使用过程中碰到很多停机问题，我们也针对性的对框架优雅停机尝试研究和优化，个人对dubbo代码理解有限，恳请指正。

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