Spring Boot 在关闭时，如果有请求没有响应完，在不同的容器会出现不同的结果，例如，在 Tomcat 和 Undertow 中会出现中断异常，那么就有可能对业务造成影响。所以，优雅停机非常有必要性，目前官方是没有提供很好的策略来实现。
Each SpringApplication registers a shutdown hook with the JVM to ensure that the ApplicationContext closes gracefully on exit. All the standard Spring lifecycle callbacks (such as the DisposableBean interface or the @PreDestroy annotation) can be used.
Spring Boot Application 在接收到停机信号后，可以通过 DisposableBean 接口 、 @PreDestroy 注解 或者 ContextClosedEvent 事件来处理优雅停机的相关逻辑。
版本信息Spring Boot 版本： 2.0.0.RELEASE
Tomcat 优雅停机@SpringBootApplicationpublic class Application { public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@Bean
public GracefulShutdown gracefulShutdown() { return new GracefulShutdown();
} @Bean
public ServletWebServerFactory servletContainer() {
TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory();
tomcat.addConnectorCustomizers(gracefulShutdown()); return tomcat;
}
private class GracefulShutdown implements TomcatConnectorCustomizer, ApplicationListener { private final Logger log = LoggerFactory.getLogger(GracefulShutdown.class); 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();
}
}
}
}
} Undertow 优雅停机@SpringBootApplicationpublic class Application { public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@Component
public class GracefulShutdown implements ApplicationListener { @Autowired
private GracefulShutdownWrapper gracefulShutdownWrapper; @Autowired
private ServletWebServerApplicationContext context; @Override
public void onApplicationEvent(ContextClosedEvent contextClosedEvent){
gracefulShutdownWrapper.getGracefulShutdownHandler().shutdown(); try {
UndertowServletWebServer webServer = (UndertowServletWebServer)context.getWebServer();
Field field = webServer.getClass().getDeclaredField("undertow");
field.setAccessible(true);
Undertow undertow = (Undertow) field.get(webServer);
List listenerInfo = undertow.getListenerInfo();
Undertow.ListenerInfo listener = listenerInfo.get(0);
ConnectorStatistics connectorStatistics = listener.getConnectorStatistics(); while (connectorStatistics.getActiveConnections() > 0){}
}catch (Exception e){ // Application Shutdown
}
}
}
} @Componentpublic class GracefulShutdownWrapper implements HandlerWrapper{ private GracefulShutdownHandler gracefulShutdownHandler; @Override
public HttpHandler wrap(HttpHandler handler) { if(gracefulShutdownHandler == null) { this.gracefulShutdownHandler = new GracefulShutdownHandler(handler);
} return gracefulShutdownHandler;
} public GracefulShutdownHandler getGracefulShutdownHandler() { return gracefulShutdownHandler;
}
}@Component@AllArgsConstructorpublic class UndertowExtraConfiguration { private final GracefulShutdownWrapper gracefulShutdownWrapper; @Bean
public UndertowServletWebServerFactory servletWebServerFactory() {
UndertowServletWebServerFactory factory = new UndertowServletWebServerFactory();
factory.addDeploymentInfoCustomizers(deploymentInfo -> deploymentInfo.addOuterHandlerChainWrapper(gracefulShutdownWrapper));
factory.addBuilderCustomizers(builder -> builder.setServerOption(UndertowOptions.ENABLE_STATISTICS, true)); return factory;
}
}Jetty 优雅停机默认支持所有请求完毕后再关闭，缺点：客户端接收不到响应，有待改进！
作者：Anoyi
链接：https://www.jianshu.com/p/14c0b6c389f0
