Analyze how Golang creates a daemon process and restarts smoothly

As a PHP development veteran. Used the command line to start/restart/stop operations such as nginx and PHP-FPM. Very impressed. If I were asked to develop such a system using C/C, I would definitely not have the energy to do it. However, since Golang entered my field of vision. I found it all very easy.

1) Generate daemon process

Go directly to the code:

package main

import (
    "os"
    "os/exec"
    "path/filepath"
)

func main() {
    //判 断当其是否是子进程，当父进程return之后，子进程会被 系统1 号进程接管
    if os.Getppid() != 1 {
        // 将命令行参数中执行文件路径转换成可用路径
        filePath, _ := filepath.Abs(os.Args[0])
        cmd := exec.Command(filePath, os.Args[1:]...)
        // 将其他命令传入生成出的进程
        cmd.Stdin = os.Stdin // 给新进程设置文件描述符，可以重定向到文件中
        cmd.Stdout = os.Stdout
        cmd.Stderr = os.Stderr
        cmd.Start() // 开始执行新进程，不等待新进程退出
        return
    }
}

Those who are familiar with the Linux system should know: the daemon process created by the user will be used by process No. 1 of the Linux system take over. In other words, the above code can only run on Linux systems. I have never played with Unix systems. Therefore, I cannot give specific suggestions.

I saw on the Internet that there are other ways to create a daemon process. However, I think only the source code method above seems good to me. and successfully used in projects.

For example:

os.StartProcess() 创建守护进程。
syscall.RawSyscall() 创建守护进程。

Only exec.Command is the most advanced way to create a daemon process. Best encapsulated. It is recommended to use this test.

2) Daemon process start/restart/stop

In point 1, we have successfully started a daemon process. However, we cannot use the kill command to end it. Then, start it again. Therefore, we have to use the industry’s professional approach: signals.

Any process running can receive the signal we send to it. There are many signals about Linux. You can search on Google for the keyword: Linux signal.

Go directly to the source code:

package main

import "fmt"
import "os"
import "os/signal"
import "syscall"

func main() {

    // Go signal notification works by sending `os.Signal`
    // values on a channel. We'll create a channel to
    // receive these notifications (we'll also make one to
    // notify us when the program can exit).
    sigs := make(chan os.Signal, 1)
    done := make(chan bool, 1)

    // `signal.Notify` registers the given channel to
    // receive notifications of the specified signals.
    signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)

    // This goroutine executes a blocking receive for
    // signals. When it gets one it'll print it out
    // and then notify the program that it can finish.
    go func() {
        sig := <p>There are three key points: <br>1) Register signal <br>2) Receive signal <br>3) Process signal. </p><p>As long as the creation of the daemon process and semaphore processing are integrated, commands can be implemented to manage the daemon process. </p><p>For more golang related technical articles, please visit the <a href="https://www.php.cn/be/go/" target="_blank"><strong>golang</strong></a> tutorial column! </p>

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