When writing Golang programs, we often need to handle program shutdown events. Especially in long-running programs, shutting down the program promptly and gracefully can avoid resource leaks and data corruption. This article will introduce how to handle program shutdown events gracefully in Golang.

1. Triggering of program shutdown event

When a Golang application receives an interrupt signal from the system, the program shutdown event will be triggered. Under Linux systems, interrupt signals can be manually triggered by the user or automatically generated by the system, such as Ctrl C, Ctrl Break, Kill and other signals.

2. The necessity of graceful shutdown of the program

During the running of the program, we often need to maintain and occupy some resources, such as database connections, file handles, timers, etc. When we do not release these resources in time, problems such as memory leaks or data corruption can result. The program shutdown event plays a role in handling these problems.

There are many ways to handle program shutdown events, but the most commonly used one is to gracefully shut down the program.

3. How to shut down the program gracefully

Closing the program gracefully is divided into the following three steps:

1. Register the shutdown event listening function

The registration closing event listening function is implemented through Golang's signal package. After registration, when the program receives a shutdown event, it will call the listening function for processing.

The following is a simple program that shows how to register a listening function for the shutdown event.

package main

import (
    "fmt"
    "os"
    "os/signal"
    "syscall"
    "time"
)

func main() {
    // 注冊程序關(guān)閉監(jiān)聽函數(shù)
    signals := make(chan os.Signal, 1)
    signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)

    // 等待程序關(guān)閉事件
    <-signals
    fmt.Println("收到程序關(guān)閉事件，開始優(yōu)雅關(guān)閉程序")

    // 在此處添加程序關(guān)閉前的清理操作
    time.Sleep(time.Second)
    fmt.Println("程序已關(guān)閉")
}

In the above code, we registered the listening functions of the SIGINT and SIGTERM signals through the signal.Notify() function. When the program When these two signals are received, the listening function will be started.

2. Trigger the shutdown event

In the program, we can trigger the shutdown event in any way. In the simplest case, we can emit the Ctrl C signal. But in actual scenarios, we may need to trigger the shutdown event in other ways. For example, we might start a coroutine to regularly check whether the shutdown event has been triggered so that the program can be shut down gracefully in a timely manner.

The following is a program that shows how to implement regular checking of closing events through coroutines:

package main

import (
    "fmt"
    "os"
    "os/signal"
    "syscall"
    "time"
)

func main() {
    signals := make(chan os.Signal, 1)
    signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)

    go func() {
        for {
            select {
            case <-signals:
                fmt.Println("收到程序關(guān)閉事件，開始優(yōu)雅關(guān)閉程序")
                time.Sleep(time.Second)
                fmt.Println("程序已關(guān)閉")
                os.Exit(0)
            }
        }
    }()

    fmt.Println("程序已啟動")
    for {
        time.Sleep(time.Second)
        fmt.Println("程序運行中......")
    }
}

In the above code, we implement regular checking of program closing events by starting a coroutine. When the coroutine receives a shutdown event, the program will be gracefully closed.

3. Cleaning work before the program shuts down gracefully

Before the program shuts down gracefully, we may need to complete the following cleaning work:

• Close the database Connect;
• Clear the cache;
• Close file IO;
• Wait for the coroutine to exit;

These operations help ensure the stability of the program performance and data integrity. When performing these cleaning tasks, we may need to consider the following two issues:

• Sequence issues: Cleaning work needs to be performed in a certain order;
• Timeout issues: When we find What should we do when a certain cleanup task cannot be completed in time?

Timeout issues can generally be handled through Golang's time package, such as setting the timeout through the time.WithTimeout() function or starting a coroutine. Clean up.

The following is a program that shows how to implement the cleanup work before the program is gracefully closed:

package main

import (
    "context"
    "fmt"
    "os"
    "os/signal"
    "syscall"
    "time"
)

func main() {
    signals := make(chan os.Signal, 1)
    signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)

    go func() {
        for {
            select {
            case <-signals:
                fmt.Println("收到程序關(guān)閉事件，開始優(yōu)雅關(guān)閉程序")

                // 在此處添加程序關(guān)閉前的清理操作
                ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
                go cleanup(ctx)
                <-ctx.Done()

                time.Sleep(time.Second)
                fmt.Println("程序已關(guān)閉")
                os.Exit(0)
            }
        }
    }()

    fmt.Println("程序已啟動")
    for {
        time.Sleep(time.Second)
        fmt.Println("程序運行中......")
    }
}

func cleanup(ctx context.Context) {
    fmt.Println("開始清理數(shù)據(jù)庫連接")
    time.Sleep(time.Second * 3)
    fmt.Println("數(shù)據(jù)庫連接已關(guān)閉")

    fmt.Println("開始清理緩存")
    time.Sleep(time.Second * 3)
    fmt.Println("緩存已清理完成")

    fmt.Println("開始清理文件IO")
    time.Sleep(time.Second * 3)
    fmt.Println("文件IO已關(guān)閉")

    fmt.Println("開始等待協(xié)程退出")
    time.Sleep(time.Second * 3)
    fmt.Println("協(xié)程已退出")
}

In the above code, we start a coroutine to implement the cleanup work before the program is gracefully closed. .

4. Conclusion

When writing Golang programs, the processing of program shutdown events is very important. Closing a program gracefully can avoid problems such as data corruption and resource leaks. When implementing graceful shutdown, we need to register shutdown event listening functions, trigger shutdown events, and perform cleanup work. When dealing with cleanup work, we need to take into account timeout issues and sequencing issues.

I hope this article can help you better understand how to handle program shutdown events gracefully in Golang programs. If you have other thoughts or questions, please feel free to leave a message in the comment area.

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