如何优雅停止 Springboot 运行

netkiller 2021-07-29

1439

准备工作

@PreDestroy 会在系统关闭前执行

package cn.netkiller;


import javax.annotation.PreDestroy;


import org.springframework.context.annotation.Configuration;


@Configuration
public class ShutdownConfiguration {


  public ShutdownConfiguration() {
    // TODO Auto-generated constructor stub
  }


  @PreDestroy
  public void preDestroy() {
    System.out.println("==============================");
    System.out.println("Destroying Spring");
    System.out.println("==============================");
  }


}

kill 命令演示

kill 命令本质是给进程发送终止信号，进程接收到终止信号后退出运行。

可以看到 Springboot 启动后，进程 PID 44559，现在使用 kill 命令杀死这个进程

当执行 kill 44559 你会看到下面的输出

neo@MacBook-Pro-Neo ~/workspace/microservice/test % java -jar target/test-0.0.1-SNAPSHOT.jar
Starting...


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.5.3)


2021-07-29 11:05:09.862  INFO 44559 --- [           main] cn.netkiller.Application                 : Starting Application v0.0.1-SNAPSHOT using Java 16.0.1 on MacBook-Pro-Neo.local with PID 44559 (/Users/neo/workspace/microservice/test/target/test-0.0.1-SNAPSHOT.jar started by neo in /Users/neo/workspace/microservice/test)
2021-07-29 11:05:09.865  INFO 44559 --- [           main] cn.netkiller.Application                 : No active profile set, falling back to default profiles: default
2021-07-29 11:05:11.363  WARN 44559 --- [           main] io.undertow.websockets.jsr               : UT026010: Buffer pool was not set on WebSocketDeploymentInfo, the default pool will be used
2021-07-29 11:05:11.399  INFO 44559 --- [           main] io.undertow.servlet                      : Initializing Spring embedded WebApplicationContext
2021-07-29 11:05:11.400  INFO 44559 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1451 ms
2021-07-29 11:05:12.041  INFO 44559 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 1 endpoint(s) beneath base path '/actuator'
2021-07-29 11:05:12.073  INFO 44559 --- [           main] io.undertow                              : starting server: Undertow - 2.2.9.Final
2021-07-29 11:05:12.085  INFO 44559 --- [           main] org.xnio                                 : XNIO version 3.8.4.Final
2021-07-29 11:05:12.099  INFO 44559 --- [           main] org.xnio.nio                             : XNIO NIO Implementation Version 3.8.4.Final
2021-07-29 11:05:12.197  INFO 44559 --- [           main] org.jboss.threads                        : JBoss Threads version 3.1.0.Final
2021-07-29 11:05:12.263  INFO 44559 --- [           main] o.s.b.w.e.undertow.UndertowWebServer     : Undertow started on port(s) 8080 (http)
2021-07-29 11:05:12.278  INFO 44559 --- [           main] cn.netkiller.Application                 : Started Application in 2.989 seconds (JVM running for 3.582)
2021-07-29 11:05:20.577  INFO 44559 --- [ionShutdownHook] io.undertow                              : stopping server: Undertow - 2.2.9.Final
==============================
Destroying Spring
==============================

而是用 kill -9 PID 就不会出现下面提示。

neo@MacBook-Pro-Neo ~/workspace/microservice/test % java -jar target/test-0.0.1-SNAPSHOT.jar
Starting...


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.5.3)


2021-07-29 11:08:10.857  INFO 44613 --- [           main] cn.netkiller.Application                 : Starting Application v0.0.1-SNAPSHOT using Java 16.0.1 on MacBook-Pro-Neo.local with PID 44613 (/Users/neo/workspace/microservice/test/target/test-0.0.1-SNAPSHOT.jar started by neo in /Users/neo/workspace/microservice/test)
2021-07-29 11:08:10.860  INFO 44613 --- [           main] cn.netkiller.Application                 : No active profile set, falling back to default profiles: default
2021-07-29 11:08:12.377  WARN 44613 --- [           main] io.undertow.websockets.jsr               : UT026010: Buffer pool was not set on WebSocketDeploymentInfo, the default pool will be used
2021-07-29 11:08:12.411  INFO 44613 --- [           main] io.undertow.servlet                      : Initializing Spring embedded WebApplicationContext
2021-07-29 11:08:12.411  INFO 44613 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1466 ms
2021-07-29 11:08:13.046  INFO 44613 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 1 endpoint(s) beneath base path '/actuator'
2021-07-29 11:08:13.081  INFO 44613 --- [           main] io.undertow                              : starting server: Undertow - 2.2.9.Final
2021-07-29 11:08:13.100  INFO 44613 --- [           main] org.xnio                                 : XNIO version 3.8.4.Final
2021-07-29 11:08:13.114  INFO 44613 --- [           main] org.xnio.nio                             : XNIO NIO Implementation Version 3.8.4.Final
2021-07-29 11:08:13.206  INFO 44613 --- [           main] org.jboss.threads                        : JBoss Threads version 3.1.0.Final
2021-07-29 11:08:13.275  INFO 44613 --- [           main] o.s.b.w.e.undertow.UndertowWebServer     : Undertow started on port(s) 8080 (http)
2021-07-29 11:08:13.290  INFO 44613 --- [           main] cn.netkiller.Application                 : Started Application in 3.195 seconds (JVM running for 3.808)
[1]    44613 killed     java -jar target/test-0.0.1-SNAPSHOT.jar

这是因为 kill 命令会给进程发送终止信号，进程会正常退出.

什么是正常退出呢？例如:

完成为运行的逻辑
将为写入磁盘的文件后写入后退出
执行完SQL并关闭数据库
写入缓存，并关闭 redis
完成用户请求，并关闭链接

这就是为什么当我们正常关闭程序需要等待很长时间，如果我们此时没有运行状态显示，也没有通过日志反应执行状态，就会认为程序死了。其实此时程序可能尽职尽责的在工作，将未完成的工作完成，然后一步步正常退出。

尤其是多线程的程序，退出时需要等待每个线程完成请求，需要很长时间，我们常常因为升级时间紧迫而使用 kill -9 强行杀死进程，这会带来很多问题。

kill -9 的弊端：

程序执行一半被强行退出，用户端会出现 Timeout 超时
文件写入一半被终止，如果是文本文件只有一半内容；如果是二进制文件会造成损坏
数据库操作一组SQL，只执行了一半，会产生脏数据；如果使用事务处理会引起回滚；

Ctrl + C 与 kill 没有区别，也是给进程发送终止信号，现在我们来演示一下。

neo@MacBook-Pro-Neo ~/workspace/microservice/test % java -jar target/test-0.0.1-SNAPSHOT.jar
Starting...
  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.5.3)


2021-07-29 11:04:42.657  INFO 44546 --- [           main] cn.netkiller.Application                 : Starting Application v0.0.1-SNAPSHOT using Java 16.0.1 on MacBook-Pro-Neo.local with PID 44546 (/Users/neo/workspace/microservice/test/target/test-0.0.1-SNAPSHOT.jar started by neo in /Users/neo/workspace/microservice/test)
2021-07-29 11:04:42.660  INFO 44546 --- [           main] cn.netkiller.Application                 : No active profile set, falling back to default profiles: default
2021-07-29 11:04:44.212  WARN 44546 --- [           main] io.undertow.websockets.jsr               : UT026010: Buffer pool was not set on WebSocketDeploymentInfo, the default pool will be used
2021-07-29 11:04:44.246  INFO 44546 --- [           main] io.undertow.servlet                      : Initializing Spring embedded WebApplicationContext
2021-07-29 11:04:44.246  INFO 44546 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1502 ms
2021-07-29 11:04:44.857  INFO 44546 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 1 endpoint(s) beneath base path '/actuator'
2021-07-29 11:04:44.889  INFO 44546 --- [           main] io.undertow                              : starting server: Undertow - 2.2.9.Final
2021-07-29 11:04:44.902  INFO 44546 --- [           main] org.xnio                                 : XNIO version 3.8.4.Final
2021-07-29 11:04:44.916  INFO 44546 --- [           main] org.xnio.nio                             : XNIO NIO Implementation Version 3.8.4.Final
2021-07-29 11:04:45.002  INFO 44546 --- [           main] org.jboss.threads                        : JBoss Threads version 3.1.0.Final
2021-07-29 11:04:45.068  INFO 44546 --- [           main] o.s.b.w.e.undertow.UndertowWebServer     : Undertow started on port(s) 8080 (http)
2021-07-29 11:04:45.084  INFO 44546 --- [           main] cn.netkiller.Application                 : Started Application in 3.149 seconds (JVM running for 3.748)
^C2021-07-29 11:04:47.082  INFO 44546 --- [ionShutdownHook] io.undertow                              : stopping server: Undertow - 2.2.9.Final
==============================
Destroying Spring
==============================

容器中如何优雅关闭 Springboot

容器与进程模式并没有什么区别，我们给容器发送终止信号，容器会转发给 Springboot。

理论归理论，我们还是需要亲自实践，这样才能理解更深刻。

准备实验环境和素材，下面是 docker-compose.yaml 编排文件

version: '3.9'
  
services:
  spring:
    image: openjdk:latest
    container_name: spring
    restart: always
    hostname: www.netkiller.cn
    environment:
      TZ: Asia/Shanghai
      JAVA_OPTS: -Xms256m -Xmx512m -XX:MetaspaceSize=128m -XX:MaxMetaspaceSize=512m
    ports:
      - 8099:8080
    volumes:
      - ./test-0.0.1-SNAPSHOT.jar:/app/test-0.0.1-SNAPSHOT.jar
    entrypoint: java -jar /app/test-0.0.1-SNAPSHOT.jar
    command:
      --spring.profiles.active=dev
      --server.port=8080

实验步骤

运行容器：docker-compose up
观察容器：docker-compose logs -f
停止容器：

运行容器

[root@localhost netkiller.cn]# docker-compose up -d
Starting spring ... done

观察容器日志

[root@localhost netkiller.cn]# docker-compose logs -f
spring    | Starting...
spring    | 
spring    |   .   ____          _            __ _ _
spring    |  /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
spring    | ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
spring    |  \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
spring    |   '  |____| .__|_| |_|_| |_\__, | / / / /
spring    |  =========|_|==============|___/=/_/_/_/
spring    |  :: Spring Boot ::                (v2.5.3)
spring    | 
spring    | 2021-07-29 11:29:34.556  INFO 1 --- [           main] cn.netkiller.Application                 : Starting Application v0.0.1-SNAPSHOT using Java 16.0.2 on www.netkiller.cn with PID 1 (/app/test-0.0.1-SNAPSHOT.jar started by root in /)
spring    | 2021-07-29 11:29:34.559  INFO 1 --- [           main] cn.netkiller.Application                 : The following profiles are active: dev
spring    | 2021-07-29 11:29:35.903  WARN 1 --- [           main] io.undertow.websockets.jsr               : UT026010: Buffer pool was not set on WebSocketDeploymentInfo, the default pool will be used
spring    | 2021-07-29 11:29:35.921  INFO 1 --- [           main] io.undertow.servlet                      : Initializing Spring embedded WebApplicationContext
spring    | 2021-07-29 11:29:35.921  INFO 1 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1274 ms
spring    | 2021-07-29 11:29:36.411  INFO 1 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 1 endpoint(s) beneath base path '/actuator'
spring    | 2021-07-29 11:29:36.437  INFO 1 --- [           main] io.undertow                              : starting server: Undertow - 2.2.9.Final
spring    | 2021-07-29 11:29:36.444  INFO 1 --- [           main] org.xnio                                 : XNIO version 3.8.4.Final
spring    | 2021-07-29 11:29:36.451  INFO 1 --- [           main] org.xnio.nio                             : XNIO NIO Implementation Version 3.8.4.Final
spring    | 2021-07-29 11:29:36.511  INFO 1 --- [           main] org.jboss.threads                        : JBoss Threads version 3.1.0.Final
spring    | 2021-07-29 11:29:36.547  INFO 1 --- [           main] o.s.b.w.e.undertow.UndertowWebServer     : Undertow started on port(s) 8080 (http)
spring    | 2021-07-29 11:29:36.560  INFO 1 --- [           main] cn.netkiller.Application                 : Started Application in 2.48 seconds (JVM running for 2.923)

停止容器

[root@localhost netkiller.cn]# docker ps | grep spring
8901384d1973   openjdk:latest                "java -jar /app/test…"   3 minutes ago   Up About a minute   0.0.0.0:8099->8080/tcp, :::8099->8080/tcp                                              spring
[root@localhost netkiller.cn]# docker stop spring
spring
[root@localhost netkiller.cn]# docker ps | grep spring

在观察日志

spring    | 2021-07-29 11:31:31.807  INFO 1 --- [ionShutdownHook] io.undertow                              : stopping server: Undertow - 2.2.9.Final
spring    | ==============================
spring    | Destroying Spring
spring    | ==============================
spring exited with code 143

现在可以看到 Springboot 是正常退出的

下面我们再做一个实验 docker kill

[root@localhost netkiller.cn]# docker-compose start
Starting spring ... done


[root@localhost netkiller.cn]# docker-compose logs -f
    
[root@localhost netkiller.cn]# docker kill spring
spring

此时再观察日志，只输出了一行。

spring exited with code 137

结论，docker kill = kill -9

现在你应该明白什么时候该使用什么命令终止程序了吧，同时我们在写程序的时候，也应该将程序的运行状态反应出来，在我们停止程序运行的时候，可以去观察进程的状态，而不是半天没有反应，只能怀疑进程死了，必须执行B计划（kill -9）这会造成很多数据丢失的问题。

写入PID文件

我们明白了 kill 的原理后，常常需要与 pid 打交道，使用 ps 命令是可以查看 pid 的，但是当我们运行多个实例的时候会常常搞混，所以最好的方式是让 springboot 把PID写入到文件中。

package cn.netkiller;


import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.ApplicationPidFileWriter;


@SpringBootApplication


public class Application {


  public static void main(String[] args) {


    System.out.println("Starting...");
    // SpringApplication.run(Application.class, args);


    SpringApplication springApplication = new SpringApplication(Application.class);
    springApplication.addListeners(new ApplicationPidFileWriter());
    springApplication.run(args);
  }
}

程序运行后会在当前目录下产生一个 PID 文件

neo@MacBook-Pro-Neo ~/workspace/microservice/test % cat application.pid 
44027

修改 pid 文件位置可以配置 application.properties

server.port=8080
spring.pid.file=/tmp/spring.pid

最后说说容器，容器的进程ID永远是 1 所以配置与否自己斟酌。

[root@localhost netkiller.cn]# docker exec -it spring cat /tmp/spring.pid
1

数据库

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如何优雅停止 Springboot 运行

准备工作

kill 命令演示

容器中如何优雅关闭 Springboot

写入PID文件

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