springboot new Thread 不销毁 springboot 停止

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架构师之光 2024-07-23 21:29:14

文章标签 springboot 优雅停机 ide JVM spring 文章分类 架构后端开发

优雅停机

目前Spring Boot已经发展到了2.3.4.RELEASE，伴随着2.3版本的到来，优雅停机机制也更加完善了。

目前版本的Spring Boot 优雅停机支持Jetty, Reactor Netty, Tomcat和 Undertow 以及反应式和基于 Servlet 的 web 应用程序都支持优雅停机功能。

优雅停机的目的：

如果没有优雅停机，服务器此时直接直接关闭(kill -9)，那么就会导致当前正在容器内运行的业务直接失败，在某些特殊的场景下产生脏数据。

增加了优雅停机配置后：

在服务器执行关闭(kill -2)时，会预留一点时间使容器内部业务线程执行完毕，此时容器也不允许新的请求进入。新请求的处理方式跟web服务器有关，Reactor Netty、 Tomcat将停止接入请求，Undertow的处理方式是返回503.

新版配置

YAML配置

新版本配置非常简单，server.shutdown=graceful 就搞定了(注意，优雅停机配置需要配合Tomcat 9.0.33(含)以上版本)

server:
  port: 6080
  shutdown: graceful #开启优雅停机
spring:
  lifecycle:
    timeout-per-shutdown-phase: 20s #设置缓冲时间 默认30s

server:
  port: 6080
  shutdown: graceful #开启优雅停机
spring:
  lifecycle:
    timeout-per-shutdown-phase: 20s #设置缓冲时间 默认30s

在设置了缓冲参数timeout-per-shutdown-phase 后，在规定时间内如果线程无法执行完毕则会被强制停机。

下面我们来看下停机时，加了优雅停日志和不加的区别：

//未加优雅停机配置
Disconnected from the target VM, address: '127.0.0.1:49754', transport: 'socket'
Process finished with exit code 130 (interrupted by signal 2: SIGINT)

//未加优雅停机配置
Disconnected from the target VM, address: '127.0.0.1:49754', transport: 'socket'
Process finished with exit code 130 (interrupted by signal 2: SIGINT)

加了优雅停机配置后，可明显发现的日志 Waiting for active requests to cpmplete,此时容器将在ShutdownHook执行完毕后停止。

关闭方式

1、一定不要使用kill -9 操作，使用kill -2 来关闭容器。这样才会触发java内部ShutdownHook操作，kill -9不会触发ShutdownHook。

2、可以使用端点监控 POST 请求 /actuator/shutdown 来执行优雅关机。

添加ShutdownHook

通过上面的日志我们发现Druid执行了自己的ShutdownHook，那么我们也来添加下ShutdownHook，有几种简单的方式：

1、实现DisposableBean接口，实现destroy方法

@Slf4j
@Service
public class DefaultDataStore implements DisposableBean {


    private final ExecutorService executorService = new ThreadPoolExecutor(OSUtil.getAvailableProcessors(), OSUtil.getAvailableProcessors() + 1, 1, TimeUnit.MINUTES, new ArrayBlockingQueue<>(200), new DefaultThreadFactory("UploadVideo"));


    @Override
    public void destroy() throws Exception {
        log.info("准备优雅停止应用使用 DisposableBean");
        executorService.shutdown();
    }
}

@Slf4j
@Service
public class DefaultDataStore implements DisposableBean {


    private final ExecutorService executorService = new ThreadPoolExecutor(OSUtil.getAvailableProcessors(), OSUtil.getAvailableProcessors() + 1, 1, TimeUnit.MINUTES, new ArrayBlockingQueue<>(200), new DefaultThreadFactory("UploadVideo"));


    @Override
    public void destroy() throws Exception {
        log.info("准备优雅停止应用使用 DisposableBean");
        executorService.shutdown();
    }
}

2、使用@PreDestroy注解

@Slf4j
@Service
public class DefaultDataStore {


    private final ExecutorService executorService = new ThreadPoolExecutor(OSUtil.getAvailableProcessors(), OSUtil.getAvailableProcessors() + 1, 1, TimeUnit.MINUTES, new ArrayBlockingQueue<>(200), new DefaultThreadFactory("UploadVideo"));


    @PreDestroy
    public void shutdown() {
        log.info("准备优雅停止应用 @PreDestroy");
        executorService.shutdown();
    }

}

@Slf4j
@Service
public class DefaultDataStore {


    private final ExecutorService executorService = new ThreadPoolExecutor(OSUtil.getAvailableProcessors(), OSUtil.getAvailableProcessors() + 1, 1, TimeUnit.MINUTES, new ArrayBlockingQueue<>(200), new DefaultThreadFactory("UploadVideo"));


    @PreDestroy
    public void shutdown() {
        log.info("准备优雅停止应用 @PreDestroy");
        executorService.shutdown();
    }

}

这里注意，@PreDestroy 比 DisposableBean 先执行

关闭原理

1、使用kill pid关闭，源码很简单，大家可以看下GracefulShutdown

private void doShutdown(GracefulShutdownCallback callback) {
  List connectors = getConnectors();
  connectors.forEach(this::close);try {for (Container host : this.tomcat.getEngine().findChildren()) {for (Container context : host.findChildren()) {while (isActive(context)) {if (this.aborted) {
       logger.info("Graceful shutdown aborted with one or more requests still active");
       callback.shutdownComplete(GracefulShutdownResult.REQUESTS_ACTIVE);return;
      }
      Thread.sleep(50);
     }
    }
   }
  }catch (InterruptedException ex) {
   Thread.currentThread().interrupt();
  }
  logger.info("Graceful shutdown complete");
  callback.shutdownComplete(GracefulShutdownResult.IDLE);
 }
 private void doShutdown(GracefulShutdownCallback callback) {
  List connectors = getConnectors();
  connectors.forEach(this::close);try {for (Container host : this.tomcat.getEngine().findChildren()) {for (Container context : host.findChildren()) {while (isActive(context)) {if (this.aborted) {
       logger.info("Graceful shutdown aborted with one or more requests still active");
       callback.shutdownComplete(GracefulShutdownResult.REQUESTS_ACTIVE);return;
      }
      Thread.sleep(50);
     }
    }
   }
  }catch (InterruptedException ex) {
   Thread.currentThread().interrupt();
  }
  logger.info("Graceful shutdown complete");
  callback.shutdownComplete(GracefulShutdownResult.IDLE);
 }

2、使用端点监控 POST 请求 /actuator/shutdown关闭

因为actuator 都使用了SPI的扩展方式，所以我们看下AutoConfiguration，可以看到关键点就是ShutdownEndpoint

@Configuration(
    proxyBeanMethods = false
)
@ConditionalOnAvailableEndpoint(
    endpoint = ShutdownEndpoint.class
)
public class ShutdownEndpointAutoConfiguration {
    public ShutdownEndpointAutoConfiguration() {
    }

    @Bean(
        destroyMethod = ""
    )
    @ConditionalOnMissingBean
    public ShutdownEndpoint shutdownEndpoint() {
        return new ShutdownEndpoint();
    }
}


@Configuration(
    proxyBeanMethods = false
)
@ConditionalOnAvailableEndpoint(
    endpoint = ShutdownEndpoint.class
)
public class ShutdownEndpointAutoConfiguration {
    public ShutdownEndpointAutoConfiguration() {
    }

    @Bean(
        destroyMethod = ""
    )
    @ConditionalOnMissingBean
    public ShutdownEndpoint shutdownEndpoint() {
        return new ShutdownEndpoint();
    }
}

ShutdownEndpoint,为了节省篇幅只留了一点重要的

@Endpoint(
    id = "shutdown",
    enableByDefault = false
)
public class ShutdownEndpoint implements ApplicationContextAware {
     
    @WriteOperation
    public Map shutdown() {
        if (this.context == null) {
            return NO_CONTEXT_MESSAGE;
        } else {
            boolean var6 = false;

            Map var1;
            try {
                var6 = true;
                var1 = SHUTDOWN_MESSAGE;
                var6 = false;
            } finally {
                if (var6) {
                    Thread thread = new Thread(this::performShutdown);
                    thread.setContextClassLoader(this.getClass().getClassLoader());
                    thread.start();
                }
            }

            Thread thread = new Thread(this::performShutdown);
            thread.setContextClassLoader(this.getClass().getClassLoader());
            thread.start();
            return var1;
        }
    }
  
      private void performShutdown() {
        try {
            Thread.sleep(500L);
        } catch (InterruptedException var2) {
            Thread.currentThread().interrupt();
        }

        this.context.close();  //这里才是核心
    }
}

@Endpoint(
    id = "shutdown",
    enableByDefault = false
)
public class ShutdownEndpoint implements ApplicationContextAware {
     
    @WriteOperation
    public Map shutdown() {
        if (this.context == null) {
            return NO_CONTEXT_MESSAGE;
        } else {
            boolean var6 = false;

            Map var1;
            try {
                var6 = true;
                var1 = SHUTDOWN_MESSAGE;
                var6 = false;
            } finally {
                if (var6) {
                    Thread thread = new Thread(this::performShutdown);
                    thread.setContextClassLoader(this.getClass().getClassLoader());
                    thread.start();
                }
            }

            Thread thread = new Thread(this::performShutdown);
            thread.setContextClassLoader(this.getClass().getClassLoader());
            thread.start();
            return var1;
        }
    }
  
      private void performShutdown() {
        try {
            Thread.sleep(500L);
        } catch (InterruptedException var2) {
            Thread.currentThread().interrupt();
        }

        this.context.close();  //这里才是核心
    }
}

在调用了 this.context.close() ，其实就是AbstractApplicationContext 的close() 方法 (重点是其中的doClose())

/**
  * Close this application context, destroying all beans in its bean factory.
  * 
/**
  * Close this application context, destroying all beans in its bean factory.
  *

Delegates to {@code doClose()} for the actual closing procedure.
  * Also removes a JVM shutdown hook, if registered, as it's not needed anymore.
  * @see #doClose()
  * @see #registerShutdownHook()
  */

@Override
 public void close() {
  synchronized (this.startupShutdownMonitor) {
   doClose(); //重点：销毁bean 并执行jvm shutdown hook
   // If we registered a JVM shutdown hook, we don't need it anymore now:
   // We've already explicitly closed the context.
   if (this.shutdownHook != null) {
    try {
     Runtime.getRuntime().removeShutdownHook(this.shutdownHook);
    }
    catch (IllegalStateException ex) {
     // ignore - VM is already shutting down
    }
   }
  }
 }

后记

到这里，关于单机版本的Spring Boot优雅停机就说完了。为什么说单机？因为大家也能发现，在关闭时，其实只是保证了服务端内部线程执行完毕，调用方的状态是没关注的。

不论是Dubbo还是Cloud 的分布式服务框架，需要关注的是怎么能在服务停止前，先将提供者在注册中心进行反注册，然后在停止服务提供者，这样才能保证业务系统不会产生各种503、timeout等现象。

好在当前Spring Boot 结合Kubernetes已经帮我们搞定了这一点，也就是Spring Boot 2.3版本新功能Liveness(存活状态) 和Readiness(就绪状态)

简单的提下这两个状态：

Liveness(存活状态)：Liveness 状态来查看内部情况可以理解为health check，如果Liveness失败就就意味着应用处于故障状态并且目前无法恢复，这种情况就重启吧。此时Kubernetes如果存活探测失败将杀死Container。
Readiness(就绪状态)：用来告诉应用是否已经准备好接受客户端请求，如果Readiness未就绪那么k8s就不能路由流量过来。

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