Kill -9 pid??
Kill sends the specified information to the program. The default message is SIGTERM(15), which terminates the specified program. If you still cannot terminate the program, you can use the SIGKILL(9) message to try to forcibly remove the program. The number of a program or job can be viewed using the PS or JOBS command.
This is a complex, simple way to kill processes in Linux. What? You ask me what is a process? Please search by yourself.
I believe that many people have used the command kill -9 pid, kill the process completely, normally we use it without the above problems, but in our project there may be fatal problems.
Kill -9 Problems caused by PID
Because kill -9 is a violent delete, so it will bring serious consequences to the program, then what will bring consequences?
Take, for example, the power failure of the transfer function while adding and deducting money to two accounts? What happens at this point? For InnoDB storage engine, there is no loss because it supports transactions, but for MyISAM engine it is a disaster, why? If you have deducted money from account A and need to add money to account B, then the power failure will cause that A’s money is deducted, but B does not get the money, which is absolutely not allowed in the production environment. Kill -9 is equivalent to the effect of A sudden power failure.
Of course, if you use kill -9 to stop the service, then it is not your transaction that can guarantee the accuracy of data. At this time, you may think of distributed transaction. There is no absolute security system or architecture in the world, and distributed transactions are the same. They may also have problems. The probability is very small, and if they happen, the loss may be irreparable.
In the MyISAM engine performance of the more obvious, such as user information from two tables maintenance, administrators to modify the user information needs to be modified when two tables, but because of you kill 9 violent end project, lead to a list only change a success, it can also lead to data inconsistencies, this is the little things, because big changes again, But money, contract these important information if because of your violent deletion lead to disorder, I think it may be worse than delete library run away, at least delete library can recover, you do not know where is wrong.
So how do we end the project?
In fact, Java provides us with the ability to end a project. For example, Tomcat can use shutdown.bat/shutdown.sh to gracefully end a project.
What does it mean to end gracefully?
“
Step 1: Stop receiving requests and internal threads. Step 2: Determine if any threads are executing. Step 3: Wait for the executing thread to complete. Step 4: Stop the container.
“
The above four steps are the normal end process, so how does SpringBoot end the service normally? Please take notes in your notebook as I introduce several ways to end a service normally.
Graceful end of service
kill -15 pid
This is also a more elegant way to end a process (project), use it carefully, why? Let’s look at an example
I wrote a normal Controller method for testing
@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";
}
1234567891011
Copy the codeThe code is very simple, print: test — start to put the program to sleep for 100 seconds, then print: test — end, in the thread sleep we use kill -15 PID to end the process, do you guess test — end will print?
application.yml
server:
port: 9988
12
Copy the codeStart the project
sudo mvn spring-boot:run
1
Copy the codeThis is how Maven launches the SpringBoot project
Find the process ID for the project
sudo ps -ef |grep shutdown
1
Copy the code
sudo curl 127.0. 01.:9988/test
1
Copy the codeBack to project log
sudo kill - 15 14086
1
Copy the codeReturn to the log
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 interrupted
at 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(ServletInvocableHand lerMethod.java:105) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHan dlerAdapter.java:879) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerA dapter.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 --- end
2020- 04- 24 10:54:04.610 ERROR 14086 --- [nio- 9988.-exec- 1] o.s.web.servlet.HandlerExecutionChain : HandlerInterceptor.afterCompletion threw exception java.lang.NullPointerException: null at org.springframework.boot.actuate.metrics.web.servlet.LongTaskTimingHandlerInterceptor.stopLongTaskTimers(LongTaskTimingH andlerInterceptor.java:123) ~[spring-boot-actuator2.26..RELEASE.jar:2.26..RELEASE] at org.springframework.boot.actuate.metrics.web.servlet.LongTaskTimingHandlerInterceptor.afterCompletion(LongTaskTimingHand lerInterceptor.java:79) ~[spring-boot-actuator2.26..RELEASE.jar:2.26..RELEASE]
at org.springframework.web.servlet.HandlerExecutionChain.triggerAfterCompletion(HandlerExecutionChain.java:179) ~[spring-webmvc5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.triggerAfterCompletion(DispatcherServlet.java:1427) [spring-webmvc5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060) [spring-webmvc5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) [spring-webmvc5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) [spring-webmvc5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) [tomcat-embed-core9.033..jar:9.033.]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket9.033..jar:9.033.]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core9.033..jar:9.033.]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core9.033..jar:9.033.]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core9.033..jar:9.033.]
at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:109) [spring-boot-actuator2.26..RELEASE.jar:2.26..RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core9.033..jar:9.033.]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web5.2. 5.RELEASE.jar:5.2. 5.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1594) [tomcat-embed-core9.033..jar:9.033.]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core9.033..jar:9.033.]
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-core9.033..jar:9.033.]
at java.lang.Thread.run(Thread.java:748) [na:1.8. 0_242]
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646 566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112
Copy the code
A call to the threadinterrupt method causes sleep to throw an exceptionThe kill -15 command causes the interrupt method to be invoked immediately in order to stop the thread. It is up to the thread to decide when to stop, which is why we still see test-end. More Spring Boot video tutorials can be obtained by following wechat subscription number.
ConfigurableApplicationContext colse
So let’s see how do we do that
package com.ymy.controller;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;
@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";
}
/** * stop */
@PostMapping(value = "shutdown")
public void shutdown(){
ConfigurableApplicationContext cyx = (ConfigurableApplicationContext) context;
cyx.close();
}
}
1234567891011121314151617181920212223242526272829303132333435363738394041424344
Copy the codeCyx.close (); Why could he shut down springboot? Please look at the source code
public void close() {
synchronized(this.startupShutdownMonitor) {
this.doClose();
if(this.shutdownHook ! = null) { try { Runtime.getRuntime().removeShutdownHook(this.shutdownHook); } catch (IllegalStateException var4) { } } } }123456789101112
Copy the codeThe application registers a close hook with the JVM at startup. When we execute the colse method, we remove the close hook and the JVM knows that we need to stop the service.
Let’s look at the test results
actuator
In this way, services are stopped by introducing dependencies. The actuator provides many interfaces, such as health checks, basic information and so on, and we can also use them to gracefully shut down.
Introduction of depend on
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
12345
Copy the codeapplication.yml
server:
port: 9988
management:
endpoints:
web:
exposure:
include: shutdown
endpoint:
shutdown:
enabled: true
server:
port: 8888
12345678910111213
Copy the codeHere, I assign a new interface for the interface of the actuator, which can improve the security. Let’s test it
@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";
}
1234567891011
Copy the codeStopped service on request for test
1. The new stop springboot service class: ElegantShutdownConfig. Java
package com.ymy.config;
import org.apache.catalina.connector.Connector;
import org.springframework.boot.web.embedded.tomcat.TomcatConnectorCustomizer;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextClosedEvent;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
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("Please try a violent shutdown.");
}
} catch (InterruptedException ex) {
System.out.println("Abnormal"); Thread.currentThread().interrupt(); }}}}1234567891011121314151617181920212223242526272829303132333435363738394041
Copy the code2. Add beans to the startup class
package com.ymy;
import com.ymy.config.ElegantShutdownConfig;
import lombok.extern.slf4j.Slf4j;
import org.apache.catalina.connector.Connector;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.embedded.tomcat.TomcatConnectorCustomizer;
import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
import org.springframework.boot.web.servlet.server.ServletWebServerFactory;
import org.springframework.context.ApplicationListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.event.ContextClosedEvent;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
@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());
returntomcat; }}1234567891011121314151617181920212223242526272829303132333435363738394041
Copy the codeNow that we are configured, let’s test again. The test interface still sleeps for 10 seconds
Then you might wonder, what happens when the JVM doesn’t stop immediately when there are requests? If a new request is received while closing, the service will not receive the request.
Data Backup Operation
What should I do if I want to do a backup operation when the service stops? It’s as simple as adding an annotation to the method you want to execute: @predestroy
“
Destroy: pre – prefix abbreviation
“
So that all adds up to executing the container once before it stops, you can do backups in it, you can do downtime, etc.
Added service stop backup utility class: databackupconfig.java
package com.ymy.config;
import org.springframework.context.annotation.Configuration;
import javax.annotation.PreDestroy;
@Configuration
public class DataBackupConfig {
@PreDestroy
public void backData(){
System.out.println("Backing up data..."); }}123456789101112131415
Copy the codeLet’s test again and print the console log:
From: blog.csdn.net/qq_33220089/article/details/105708331
