spring项目优雅停机

        最近，公司项目优化重构，为了项目可以无缝上下线，如丝般顺滑，考虑到添加优雅停机功能。优雅停机包含线程池、消息、数据库、服务下线。

        jvm有钩子函数在收到kill命令后会执行回掉，可以使用这个实现优雅下线。简单介绍一下kill命令。-2类似于ctrl+c，kill -15服务正常下线会触发jvm钩子函数。kill -9系统内核直接杀死，不会触发钩子函数。

优雅下线涉及到bean的生命周期销毁。ContextClosedEvent和@PreDestroy和周期和DisposableBean参考链接

https://blog.csdn.net/qq_4384...

线程池、mq、db等都在spring的bean销毁之前下线,注意下线顺序。例子：

相同方式可以通过@Order控制顺序

 private ThreadPoolExecutor executor;

    @Bean
    @Primary
    public ThreadPoolExecutor asyncServiceExecutor() {
        executor = new ThreadPoolExecutor(5, 20, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue<>(1000), new ThreadPoolExecutor.CallerRunsPolicy());
        return executor;
    }

    @PreDestroy
    public void destroyThreadPool() {
        if (!executor.isTerminated()){
            executor.shutdown();
            try {
                executor.awaitTermination(10, TimeUnit.SECONDS);
            } catch (InterruptedException e) {
                e.printStackTrace();
                executor.shutdownNow();
            }
        }
        log.info("ThreadPoolExecutor destroyed !");
    }

dubbo下线

dubbo默认开启了优雅停机。下线分为从注册中心下线，关闭协议
2.7之后源码如下：ShutdownHookListener，继承 Spring ApplicationListener 接口，用以监听 Spring 相关事件。这里 ShutdownHookListener 仅仅监听 Spring 关闭事件，当 Spring 开始关闭，将会触发 ShutdownHookListener 内部逻辑

public class SpringExtensionFactory implements ExtensionFactory {
    private static final Logger logger = LoggerFactory.getLogger(SpringExtensionFactory.class);

    private static final Set<ApplicationContext> CONTEXTS = new ConcurrentHashSet<ApplicationContext>();
    private static final ApplicationListener SHUTDOWN_HOOK_LISTENER = new ShutdownHookListener();

    public static void addApplicationContext(ApplicationContext context) {
        CONTEXTS.add(context);
        if (context instanceof ConfigurableApplicationContext) {
            // 注册 ShutdownHook
            ((ConfigurableApplicationContext) context).registerShutdownHook();
            // 取消 AbstractConfig 注册的 ShutdownHook 事件
            DubboShutdownHook.getDubboShutdownHook().unregister();
        }
        BeanFactoryUtils.addApplicationListener(context, SHUTDOWN_HOOK_LISTENER);
    }
    // 继承 ApplicationListener，这个监听器将会监听容器关闭事件
    private static class ShutdownHookListener implements ApplicationListener {
        @Override
        public void onApplicationEvent(ApplicationEvent event) {
            if (event instanceof ContextClosedEvent) {
                DubboShutdownHook shutdownHook = DubboShutdownHook.getDubboShutdownHook();
                shutdownHook.doDestroy();
            }
        }
    }
}
通过配置dubbo.application.shutwait=30s可以设置dubbo等待时间

springboot下线

        熟悉介绍springboot优雅停机，在Springboot2.3之前需要自己实现优雅停机。2.3后自己实现了优雅停机。

springboot2.3之前的实现方式。

1、创建SafetyShutDownConfig类实现TomcatConnectorCustomizer,ApplicationListener<ContextClosedEvent>接口即可，kill -2和kill -15就可以进行测试

@Slf4j
@Configuration
public class SafetyShutDownConfig implements TomcatConnectorCustomizer, ApplicationListener<ContextClosedEvent> {

    private volatile Connector connector;
    private final int waitTime = 30;

    @Override
    public void customize(Connector connector) {
        this.connector = connector;
    }

    @Override
    public void onApplicationEvent(ContextClosedEvent contextClosedEvent) {
        this.connector.pause();
        Executor executor = this.connector.getProtocolHandler().getExecutor();
        if (executor instanceof ThreadPoolExecutor) {
            try {
                ThreadPoolExecutor threadPoolExecutor = (ThreadPoolExecutor) executor;
                threadPoolExecutor.shutdown();
                if (!threadPoolExecutor.awaitTermination(waitTime, TimeUnit.SECONDS)) {
                    log.warn("Tomcat thread pool did not shut down gracefully within " + waitTime + " seconds. Proceeding with forceful shutdown");
                }
            } catch (InterruptedException ex) {
                Thread.currentThread().interrupt();
            }
        }
    }
}

springboot2.3之后的实现

1、在配置文件中开启就可以
#开启优雅停机
server.shutdown=graceful
#优雅停机最大等待时间
spring.lifecycle.timeout-per-shutdown-phase=30s