From bd48ea556ba378514894b97de1fc262a67cf3f30 Mon Sep 17 00:00:00 2001
From: smallnest <smallnest@gmail.com>
Date: Mon, 13 Jul 2020 18:00:08 +0800
Subject: [PATCH] implement graceful restart

---
 server/gateway.go |  2 +-
 server/server.go  | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/server/gateway.go b/server/gateway.go
index 10266b1..45be3a0 100644
--- a/server/gateway.go
+++ b/server/gateway.go
@@ -20,7 +20,7 @@ import (
 
 func (s *Server) startGateway(network string, ln net.Listener) net.Listener {
 	if network != "tcp" && network != "tcp4" && network != "tcp6" {
-		log.Infof("network is not tcp/tcp4/tcp6 so can not start gateway")
+		// log.Infof("network is not tcp/tcp4/tcp6 so can not start gateway")
 		return ln
 	}
 
diff --git a/server/server.go b/server/server.go
index 410005b..570533f 100644
--- a/server/server.go
+++ b/server/server.go
@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"os"
+	"os/exec"
 	"os/signal"
 	"syscall"
 
@@ -751,6 +752,46 @@ func (s *Server) Shutdown(ctx context.Context) error {
 	return err
 }
 
+// Restart restarts this server gracefully.
+// It starts a new rpcx server with the same port with SO_REUSEPORT socket option,
+// and shutdown this rpcx server gracefully.
+func (s *Server) Restart(ctx context.Context) error {
+	pid, err := s.startProcess()
+	if err != nil {
+		return err
+	}
+	log.Infof("restart a new rpcx server: %d", pid)
+
+	// TODO: is it necessary?
+	time.Sleep(3 * time.Second)
+	return s.Shutdown(ctx)
+}
+
+func (s *Server) startProcess() (int, error) {
+	argv0, err := exec.LookPath(os.Args[0])
+	if err != nil {
+		return 0, err
+	}
+
+	// Pass on the environment and replace the old count key with the new one.
+	var env []string
+	for _, v := range os.Environ() {
+		env = append(env, v)
+	}
+
+	var originalWD, _ = os.Getwd()
+	allFiles := append([]*os.File{os.Stdin, os.Stdout, os.Stderr})
+	process, err := os.StartProcess(argv0, os.Args, &os.ProcAttr{
+		Dir:   originalWD,
+		Env:   env,
+		Files: allFiles,
+	})
+	if err != nil {
+		return 0, err
+	}
+	return process.Pid, nil
+}
+
 func (s *Server) checkProcessMsg() bool {
 	size := atomic.LoadInt32(&s.handlerMsgNum)
 	log.Info("need handle in-processing msg size:", size)