golang daemon example

server_daemon.go

package main

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

func createLogFile(fileName string) (fd *os.File, err error) {
	dir := path.Dir(fileName)
	if _, err = os.Stat(dir); err != nil && os.IsNotExist(err) {
		if err = os.MkdirAll(dir, 0755); err != nil {
			return
		}
	}

	if fd, err = os.Create(fileName); err != nil {
		return
	}

	return
}

func main() {
	if os.Getppid() != 1 {
		logFile, _ := createLogFile("main.log")
		execPath, _ := filepath.Abs(os.Args[0])
		args := append([]string{execPath}, os.Args[1:]...)
		os.StartProcess(execPath, args, &os.ProcAttr{
			Files: []*os.File{os.Stdin, logFile, logFile},
		})
		return
	}

	log.Println("pid is", os.Getpid())
	mux := http.NewServeMux()
	mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
		log.Println("Call / at", req.RemoteAddr)
		fmt.Fprintln(w, "hello,world")
	})

	server := http.Server{
		Addr:    ":8080",
		Handler: mux,
	}

	go func() {
		log.Println("Start...")
		if err := server.ListenAndServe(); err != http.ErrServerClosed && err != nil {
			log.Fatal(err)
		}
	}()

	stopSignal := make(chan os.Signal, 1)
	signal.Notify(stopSignal, syscall.SIGINT, syscall.SIGTERM)
	<-stopSignal

	server.Shutdown(context.Background())
	log.Println("bye")
}