golang 热重启
package main
import (
"context"
"fmt"
"log"
"net"
"net/http"
"os"
"os/exec"
"os/signal"
"syscall"
"time"
"flag"
)
var (
listener net.Listener
err error
server http.Server
graceful = flag.Bool("g", false, "listen on fd open 3 (internal use only)")
)
func init(){
log.SetFlags(log.Ldate | log.Lshortfile)
}
// MyHandler 控制台
type MyHandler struct {
}
func (*MyHandler)ServeHTTP(w http.ResponseWriter, r *http.Request){
log.Println("request start at ", time.Now(), r.URL.Path+"?"+r.URL.RawQuery, "request done at ", time.Now(), " pid:", os.Getpid())
time.Sleep(10 * time.Second)
fmt.Fprintln(w,"cout")
log.Println("request done at ", time.Now(), " pid:", os.Getpid() )
log.Println(r.RemoteAddr)
}
func main() {
flag.Parse()
fmt.Println("start-up at " , time.Now(), *graceful)
if *graceful {
// 这暗藏杀机，先复制fd到新的fd, 然后设置子进程exec时自动关闭父进程的fd,即“F_DUPFD_CLOEXEC”
// 要是接收到信号后，不执行这里，就会发生端口被占用的错误
f := os.NewFile(3, "")
listener, err = net.FileListener(f)
fmt.Printf( "graceful-reborn %v %v %#v \n", f.Fd(), f.Name(), listener)
}else{
listener, err = net.Listen("tcp", ":8080")
}
server := http.Server{
Handler: &MyHandler{},
ReadTimeout: 6 * time.Second,
}
log.Printf("Actual pid is %d\n", syscall.Getpid())
if err != nil {
log.Println(err)
return
}
log.Printf(" listener: %v\n", listener)
go func(){//不要阻塞主进程
err := server.Serve(listener)
if err != nil {
log.Println(err)
}
}()
//signals
func(){
ch := make(chan os.Signal, 1)
signal.Notify(ch, syscall.SIGINT)
for{
//阻塞主进程， 不停的监听系统信号
sig := <- ch
log.Printf("signal: %v", sig)
ctx, _ := context.WithTimeout(context.Background(), 20*time.Second) // 这里就是上下文
switch sig {
// 我用终止信号，做例子，大家可以使用别的信号
case syscall.SIGINT:
println("signal cause reloading")
signal.Stop(ch)
{
// fork子进程
tl, ok := listener.(*net.TCPListener)
if !ok {
log.Println("listener is not tcp listener")
return
}
// 接收父进程的socket文件描述符
currentFD, err := tl.File()
if err != nil {
log.Println("acquiring listener file failed")
return
}
// 好坑啊，这里，“-g"是必须的，因为再次运行之后，g=true
cmd := exec.Command(os.Args[0],"-g")
log.Println(cmd.Args)
// currentFD 这里是子进程了，fork的时候，将socket文件描述传给子进程
// 父进程将socket文件描述符传递给子进程可以通过命令行
// f := os.NewFile(3, "") []*os.File{currentFD} 想到对应
cmd.ExtraFiles, cmd.Stdout,cmd.Stderr = []*os.File{currentFD} ,os.Stdout, os.Stderr
err = cmd.Start()
// 重启运行
if err != nil {
log.Println("cmd.Start fail: ", err)
return
}
log.Println("forked new pid : ",cmd.Process.Pid)
}
// 阻塞到父进程将所有的请求处理完毕
server.Shutdown(ctx) // 优雅的等待关闭
log.Println("graceful shutdown at ", time.Now())
}
}
}()
}