How to restart smoothly in golang

In the fields of front-end development, back-end development and DevOps, smooth restart is a very important technology. When an application needs to be updated without interrupting existing requests, graceful restart makes the update process smoother. Graceful restart is a relatively new technology in Golang, but as Golang gets more attention, it has become a must-have feature. This article will introduce how to implement smooth restart in Golang.

What is a smooth restart?

Graceful restart is an application update technique in which the update process occurs without disturbing existing requests. A traditional restart means stopping the application and starting a fresh instance. Doing so will cause incoming requests to become unresponsive until the new instance finishes starting up and takes over the requests. Graceful restart solves this problem, allowing the application update process to occur inside the existing instance.

Why do we need a smooth restart?

Without a graceful restart, every time an application needs to be updated, it results in a period of unavailability. This causes inconvenience to clients/users. A graceful restart can avoid this problem and make the application more pleasant and resilient, which is especially useful during times of high traffic.

Golang’s built-in http optimization

In Golang, http.Server is our commonly used Web framework. It provides us with many options, including graceful restart. http.Server has a Shutdown method that stops the server without interrupting operations until all client connections have been closed.

When we handle existing connections by listening to system SIGINT (Ctrl C/kill), SIGTERM (kill) and other signals and calling http.Server.Shutdown(), we can stop the server. While stopping, we can wait for all handlers to complete or close the operation after a timeout.

The following is a short example.

package main

import (
    "context"
    "fmt"
    "log"
    "net/http"
    "os"
    "os/signal"
    "syscall"
    "time"
)

func main() {
    // 创建我们的HTTP Server，参数为 Mux/Router 实例
    srv := &http.Server{
        Addr: ":8080",
        // 服务器转发请求给自己，重写了请求的url(必填)
        Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            w.Write([]byte("Welcome to my website!"))
        }),
    }

    // 新开 goroutine 监听用户信号(操作系统可以选择向进程发送的信号)
    go func() {
        sigs := make(chan os.Signal, 1)
        // 常见用户信号 ctrl+c, kill ,sigterm 等
        signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)

        <-sigs

        // 创建新的 context 用于调用 shutdown 方法
        ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
        defer cancel()

        if err := srv.Shutdown(ctx); err != nil {
            log.Fatal("Server forced to shutdown:", err)
        }

        log.Println("Server gracefully stopped")
    }()

    log.Println("Server started at", srv.Addr)

    // 最终函数会阻塞在这里，等待用户信号
    if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
        log.Fatal("Server exited:", err)
    }
}

When using an actual server in this example, we need to ensure that the errors returned by http.Server.Serve() are not overwritten, such as http.ErrServerClosed. This can be used to correctly handle operations (such as immediate errors) to avoid unexpected server shutdown or server restart.

You need to ensure that the passed context is not closed before handling the wait (depending on your code implementation), So that the waiting operation has enough time to complete the task.

Summary

Smooth restart can help us avoid transient unavailability caused by application restart, and is essential for any application that requires high availability. As a high-performance, easy-to-develop and expand language, Golang should naturally support smooth restart. In Golang, you can simply use the http.Server.Shutdown() method to achieve smooth restart, and then implement your business logic on this basis.

The above is the detailed content of How to restart smoothly in golang. For more information, please follow other related articles on the PHP Chinese website!