服务优雅重启 facebook/grace 简介

func main() {
    // 用于协程间通信，由信号监控协程，发消息给服务关闭协程
	stopC := make(chan struct{})
    // 监听服务退出信号
	go watchSignal(stopC)
    // 执行关闭服务前的操作，或手动关闭服务
	go shutdownServer(stopC)
    // 启动服务
    s.Serve()
    log.Info("服务已退出...")
}

// watchSignal 监听信号
func watchSignal(stop chan<- struct{}) {
	defer func() {
		if e := recover(); e != nil {
			errMsg := fmt.Sprintf("##catchSignal panic#main# error:%s", e)
			log.Fatal(errMsg)
		}
	}()
	// 保存PID
	if pid := syscall.Getpid(); pid != 1 {
		ioutil.WriteFile("server.pid", []byte(strconv.Itoa(pid)), 0777)
		defer os.Remove("server.pid")
	}
	// 创建 os.Signal 类型变量，用于接收系统信号
	signC := make(chan os.Signal, 1)
	// 使用 signal.Notify 函数将 os.Signal 变量和系统信号绑定
	signal.Notify(signC, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
	for {
		// 监听信号
		s := <-signC
		log.Info("收到信号 -- " + s.String())
		switch s {
		case syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT:
            // 释放资源
			releaseResource()
            // 开始关闭服务
			close(stop)
		default:
		}
	}
}

// 执行关闭服务前的操作，或手动关闭服务
func shutdownServer(stop <-chan struct{}) {
	<-stop
	log.Info("服务正在关闭...")
	// 执行服务退出逻辑
}

服务优雅重启，除了要优化退出旧服务之外，还需要考虑旧进程的请求处理，新请求的平滑切换。

package main

import (
	"flag"
	"fmt"
	"net/http"
	"os"
	"time"

	"github.com/facebookgo/grace/gracehttp"
)

var (
	address0 = flag.String("a0", ":48567", "Zero address to bind to.")
	address1 = flag.String("a1", ":48568", "First address to bind to.")
	address2 = flag.String("a2", ":48569", "Second address to bind to.")
	now      = time.Now()
)

func main() {
	flag.Parse()
	gracehttp.Serve(
		&http.Server{Addr: *address0, Handler: newHandler("Zero  ")},
		&http.Server{Addr: *address1, Handler: newHandler("First ")},
		&http.Server{Addr: *address2, Handler: newHandler("Second")},
	)
}

func newHandler(name string) http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/sleep/", func(w http.ResponseWriter, r *http.Request) {
		duration, err := time.ParseDuration(r.FormValue("duration"))
		if err != nil {
			http.Error(w, err.Error(), 400)
			return
		}
		time.Sleep(duration)
		fmt.Fprintf(w, "%s started at %s slept for %d nanoseconds from pid %d.\n",
			name, now, duration.Nanoseconds(), os.Getpid())
	})
	return mux
}