How to end a process in nodejs

Node.js is a JavaScript running environment based on the V8 engine and is currently one of the most commonly used technologies for front-end development. In Node.js, process is a very important concept. Every Node.js application starts a process to run. In some cases, we need to manually end the running process. This article will introduce you how to end the Node.js process.

Program abort signal

In Node.js, a process can receive multiple signals, and these signals can be used to control the behavior of the process, including aborting the process. Some common signals include:

• SIGINT: Triggered by user input Ctrl C, usually used to terminate the process.
• SIGTERM: Usually sent by the operating system to indicate that the process needs to terminate normally.
• SIGHUP: Usually indicates that the terminal connection is interrupted.
• SIGBREAK: Triggered under Windows system, user inputs Ctrl Break.

When the process receives any of these signals, Node.js will trigger the exit() event of the process object. This event allows us to Perform some cleanup operations before the process ends.

Ending through code

We can directly call the process.exit() method to end the process in the code. process.exit() The method supports passing in an integer parameter, which is called the exit code. The exit code is 0 when the process terminates normally, otherwise it is a non-zero value. Like this:

const code = 1;
process.exit(code);

In this case, the process will end with exit code 1, which can be done in the terminal via echo $?(Mac/Linux) or echo %errorlevel% (Windows) to view the exit code.

In addition, before ending the process, you can listen to the exit() event to perform some cleanup operations:

process.on('exit', code => {
  // 执行一些清理操作
  console.log(`进程退出，退出码：${code}`);
});

Use the kill command

In addition to code, we can also use the operating system's kill command to end the process. kill The command is usually used to send signals to the process to control the process behavior, for example:

# 给进程 ID 为 1234 的进程，发送 SIGTERM 信号结束进程
kill -SIGTERM 1234

If no parameters are passed, the kill command sends the SIGTERM signal by default, which will cause the process to terminate gracefully. For example:

# 结束进程 ID 为 1234 的进程
kill 1234

Use pm2 to manage processes

pm2 is a very powerful process management tool that can be widely used in production environments. pm2 You can start, restart, and stop applications through the command line, and monitor the application running status. It is very simple to use pm2 to manage the process. You only need to run the following command in the application directory:

# 启动应用程序
pm2 start app.js

# 重启应用程序
pm2 restart app.js

# 停止应用程序
pm2 stop app.js

In addition, pm2 is also responsible for monitoring the running status and logs of the application. Output, very suitable for use in production environments.

In short, there are many ways to end the Node.js process. The most common way is to call the process.exit() method through code or use pm2Manage process. Either way, we should ensure that the process exits normally to avoid unnecessary system burden caused by the process running in the background.

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