@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:
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:
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
[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。
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
扫码关注腾讯云开发者
领取腾讯云代金券
Copyright © 2013 - 2025 Tencent Cloud. All Rights Reserved. 腾讯云 版权所有
深圳市腾讯计算机系统有限公司 ICP备案/许可证号:粤B2-20090059 深公网安备号 44030502008569
腾讯云计算(北京)有限责任公司 京ICP证150476号 | 京ICP备11018762号 | 京公网安备号11010802020287
Copyright © 2013 - 2025 Tencent Cloud.
All Rights Reserved. 腾讯云 版权所有