优雅地关闭程序
kill -9
kill -9 pid :彻底杀死进程的意思,一般情况使用它没有问题,但是在项目中使用它就有可能存在致命的问题。
kill 可将指定的信息送至程序。预设的信息为SIGTERM(15),可将指定程序终止。若仍无法终止该程序,可使用SIGKILL(9)信息尝试强制删除程序。程序或工作的编号可利用ps指令或jobs指令查看(这段话来自菜鸟教程)。
讲的这个复杂,简单点来说就是用来杀死linux中的进程。
kill -9 pid 带来的问题:
由于kill -9 属于暴力删除,所以会给程序带来比较严重的后果,那究竟会带来什么后果呢?
举个栗子:转账功能,再给两个账户进行加钱扣钱的时候突然断电了?这个时候会发生什么事情?对于InnoDB存储引擎来说,没有什么损失,因为它支持事务,但是对于MyISAM引擎来说那简直就是灾难,为什么?假如给A账户扣了钱,现在需要将B账户加钱,这个时候停电了,就会造成,A的钱被扣了,但是B没有拿到这笔钱,这在生产环境是绝对不允许的,kill -9 相当于突然断电的效果。
当然了,像转账这种,肯定不是使用MyISAM引擎,但是如今分布式火了起来,跨服务转账已经是很平常的事情,这种时候如果使用kill -9 去停止服务,那就不是你的事务能保证数据的准确性了,这个时候你可能会想到分布式事务,这个世界上没有绝对的安全系统或者架构,分布式事务也是一样,他也会存在问题,概率很小,如果一旦发生,损失有可能是无法弥补的,所以一定不能使用kill -9 去停止服务,因为你不知道他会造成什么后果。
在MyISAM引擎中表现的更明显,比如用户的信息由两张表维护,管理员修改用户信息的时候需要修改两张表,但由于你的kill -9 暴力结束项目,导致只修改成功了一张表,这也会导致数据的不一致性,这是小事,因为大不了再修改一次,但是金钱、合同这些重要的信息如果由于你的暴力删除导致错乱,我觉得可能比删库跑路还严重,至少删库还能恢复,你这个都不知道错在哪里。
优雅结束服务
那应该怎么结束项目呢?
其实java提供了结束项目的功能,比如:tomcat可以使用 shutdown.bat/shutdown.sh 进行优雅结束。
什么叫优雅结束?
第一步:停止接收请求和内部线程。
第二步:判断是否有线程正在执行。
第三步:等待正在执行的线程执行完毕。
第四步:停止容器。
以上四步才是正常的结束流程,那Spring Boot怎么正常结束服务呢?
kill -15 pid
这种方式也会比较优雅的结束进程(项目),使用他的时候需要慎重,为什么呢?
来看个例子
我写了一个普通的controller方法做测试
@GetMapping(value = "/test")
public String test(){
log.info("test --- start");
try {
Thread.sleep(100000);
} catch (InterruptedException e) {
e.printStackTrace();
}
log.info("test --- end");
return "test";
}
代码很简单,打印:test — start之后让让程序休眠100秒,然后再打印:test — end,在线程休眠中我们使用kill -15 pid来结束这个进程,你们猜 test — end会被打印吗?
application.yml配置
server:
port: 9988
启动项目
sudo mvn spring-boot:run
这是maven启动springboot项目的方式
看到这个就代表项目启动成了
找到项目的进程id
sudo ps -ef |grep shutdown
这个就是项目的进程号,接下来先测试test接口,让线程进入休眠状态,然后再使用kill -15 14086停止项目
sudo curl 127.0.0.1:9988/test
回到项目日志
发现请求已经到达服务,并且线程已经成功进入休眠,现在kill -15 14086结束进程
sudo kill -15 14086
回到日志
2020-04-24 10:53:14.939 INFO 14086 --- [nio-9988-exec-1] com.ymy.controller.TestController : test --- start
2020-04-24 10:54:02.450 INFO 14086 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor'java.lang.InterruptedException: sleep interruptedat java.lang.Thread.sleep(Native Method)at com.ymy.controller.TestController.test(TestController.java:26)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:109)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1594)at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:748)2020-04-24 10:54:04.574 INFO 14086 --- [nio-9988-exec-1] com.ymy.controller.TestController : test --- end2020-04-24 10:54:04.610 ERROR 14086 --- [nio-9988-exec-1] o.s.web.servlet.HandlerExecutionChain : HandlerInterceptor.afterCompletion threw exceptionjava.lang.NullPointerException: nullat org.springframework.boot.actuate.metrics.web.servlet.LongTaskTimingHandlerInterceptor.stopLongTaskTimers(LongTaskTimingHandlerInterceptor.java:123) ~[spring-boot-actuator-2.2.6.RELEASE.jar:2.2.6.RELEASE]at org.springframework.boot.actuate.metrics.web.servlet.LongTaskTimingHandlerInterceptor.afterCompletion(LongTaskTimingHandlerInterceptor.java:79) ~[spring-boot-actuator-2.2.6.RELEASE.jar:2.2.6.RELEASE]at org.springframework.web.servlet.HandlerExecutionChain.triggerAfterCompletion(HandlerExecutionChain.java:179) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.springframework.web.servlet.DispatcherServlet.triggerAfterCompletion(DispatcherServlet.java:1427) [spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060) [spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) [spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) [spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.33.jar:9.0.33]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:109) [spring-boot-actuator-2.2.6.RELEASE.jar:2.2.6.RELEASE]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1594) [tomcat-embed-core-9.0.33.jar:9.0.33]at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.33.jar:9.0.33]at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_242]at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_242]at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.33.jar:9.0.33]at java.lang.Thread.run(Thread.java:748) [na:1.8.0_242]
居然报错了,但是test — end是打印出来了,为什么会报错呢?这就和sleep这个方法有关了,在线程休眠期间,当调用线程的interrupt方法的时候会导致sleep抛出异常,这里很明显就是kill -15 这个命令会让程序马上调用线程的interrupt方法,目的是为了让线程停止,虽然让线程停止,但线程什么时候停止还是线程自己说的算,这就是为什么还能看到:test — end的原因。
ConfigurableApplicationContext colse
先看怎么实现
@RestController
@Slf4j
public class TestController implements ApplicationContextAware {
private ApplicationContext context;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.context = applicationContext;
}
@GetMapping(value = "/test")
public String test(){
log.info("test --- start");
try {
Thread.sleep(100000);
} catch (InterruptedException e) {
e.printStackTrace();
}
log.info("test --- end");
return "test";
}
/**
* 停机
*/
@PostMapping(value = "shutdown")
public void shutdown(){
ConfigurableApplicationContext cyx = (ConfigurableApplicationContext) context;
cyx.close();
}
}
重点在:cyx.close();,为什么能停止Spring Boot项目呢?
请看源码
public void close() {
synchronized(this.startupShutdownMonitor) {
this.doClose();
if (this.shutdownHook != null) {
try {
Runtime.getRuntime().removeShutdownHook(this.shutdownHook);
} catch (IllegalStateException var4) {
}
}
}
}
程序在启动的时候向jvm注册了一个关闭钩子,在执行colse方法的时候会删除这个关闭钩子,jvm就会知道这是需要停止服务。
看测试结果
很明显,也出发了线程的interrupt方法导致线程报错,原理和kill -15差不多。
actuator
这种方式是通过引入依赖的方式停止服务,actuator提供了很多接口,比如健康检查,基本信息等等,也可以使用他来优雅的停机。
引入依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
application.yml
server:
port: 9988
management:
endpoints:
web:
exposure:
include: shutdown
endpoint:
shutdown:
enabled: true
server:
port: 8888
这里对actuator的接口重新给定了一个接口,这样可提高安全性,下面来测试一下
@RequestMapping(value = "/test",method = RequestMethod.GET)
public String test(){
System.out.println("test --- start");
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("test --- end");
return "hello";
}
在请求test途中停止服务
发现发送停止服务请求之后还返回了提示信息,很人性化,看看控制台
test — end被执行了,不过在停止线程池的时候还是调用了线程的interrupt方法,导致sleep报错,这三种方式都可以比较优雅的停止Spring Boot服务,如果项目中存在线程休眠,希望10秒以后再停止服务可以吗?肯定是可以的,只需要稍微做点修改就可以了。
配置10秒后再停止服务
- 新增停止Spring Boot服务类:ElegantShutdownConfig.java
public class ElegantShutdownConfig implements TomcatConnectorCustomizer, ApplicationListener<ContextClosedEvent> {
private volatile Connector connector;
private final int waitTime = 10;
@Override
public void customize(Connector connector) {
this.connector = connector;
}
@Override
public void onApplicationEvent(ContextClosedEvent event) {
connector.pause();
Executor executor = connector.getProtocolHandler().getExecutor();
if (executor instanceof ThreadPoolExecutor) {
try {
ThreadPoolExecutor threadPoolExecutor = (ThreadPoolExecutor) executor;
threadPoolExecutor.shutdown();
if (!threadPoolExecutor.awaitTermination(waitTime, TimeUnit.SECONDS)) {
System.out.println("请尝试暴力关闭");
}
} catch (InterruptedException ex) {
System.out.println("异常了");
Thread.currentThread().interrupt();
}
}
}
}
- 在启动类中加入bean
@SpringBootApplication
public class ShutdownServerApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(ShutdownServerApplication.class, args);
run.registerShutdownHook();
}
@Bean
public ElegantShutdownConfig elegantShutdownConfig() {
return new ElegantShutdownConfig();
}
@Bean
public ServletWebServerFactory servletContainer() {
TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory();
tomcat.addConnectorCustomizers(elegantShutdownConfig());
return tomcat;
}
}
这样就配置好了,再来测试一遍,test的接口还是休眠10秒
发现这次没有报错了,他是等待了一段时间之后再结束的线程池,这个时间就是在ElegantShutdownConfig类中配置的waitTime。
那可能会有疑问了,jvm没有立即停止,那这个时候在有请求会发生什么呢?如果关闭的时候有新的请求,服务将不在接收此请求。
数据备份操作
如果想在服务停止的时候做点备份操作啥的,应该怎么做呢?只要在要执行的方法上添加一个注解即可:
@PreDestroy:Destroy:消灭、毁灭,pre:前缀缩写
所以合在一起的意思就是在容器停止之前执行一次,可以在这里面做备份操作,也可以做记录停机时间等。
新增服务停止备份工具类:DataBackupConfig.java
@Configuration
public class DataBackupConfig {
@PreDestroy
public void backData(){
System.out.println("正在备份数据。。。。。。。。。。。");
}
}
再来测试然后打印控制台日志: