warrend init statup properly in /var/run and close and respect only one

instance

Makefile

@@ -18,7 +18,9 @@ clean:
 install:
 	cp cmd/warren/warren /usr/bin
 	cp cmd/warrend/warrend /usr/bin
+	mkdir /var/run/warrend
 
 uninstall:
 	rm /usr/bin/warren
 	rm /usr/bin/warrend
+	rmdir /var/run/warrend

cmd/warren/main.go

@@ -49,5 +49,4 @@ func main() {
 	}
 
 	icmd.(*warren.Command).Exec(args[1:])
-
 }

cmd/warrend/main.go

@@ -11,6 +11,8 @@ import (
 	"syscall"
 )
 
+var cmdSock net.Listener
+
 type SockCommand struct {
 	warren.Command
 	Run func(cmd *SockCommand, c net.Conn, args ...string)
@@ -52,19 +54,64 @@ func sockCmdHandle(c net.Conn) {
 		return
 	}
 	icmd.(*SockCommand).Exec(c, args[1:])
-	warren.WriteStringz(c, "echo: "+data)
+}
+
+// determine if warrend is already running
+func checkRunning() bool {
+	if pfile, err := os.Open(warren.WarrendPidFile()); err == nil {
+		// pid file exists
+		var pid int
+		n, err := fmt.Fscanf(pfile, "%d", &pid)
+		if n == 0 || err != nil {
+			// read error
+			return false
+		}
+		// is there a runnign process with the pid?
+		err = syscall.Kill(pid, 0)
+		return err == nil
+
+	} else {
+		// pid file does not exist
+		return false
+	}
+}
+
+func initRunning() {
+	// rm old sock
+	os.Remove(warren.CmdSockAddr())
+	// drop down pid
+	pidfile, err := os.Create(warren.WarrendPidFile())
+	if err != nil {
+		log.Fatal("Could not create pidfile: ", warren.WarrendPidFile(), " : ", err)
+	}
+	pid := os.Getpid()
+	fmt.Fprintf(pidfile, "%d", pid)
+	pidfile.Close()
+
+	cmdSock, err = net.Listen(warren.CmdSockType(), warren.CmdSockAddr())
+	if err != nil {
+		fmt.Println(cmdSock)
+		Shutdown()
+		log.Fatal("Listen on sock error:", err)
+	}
+
+}
+
+func Shutdown() {
+	os.Remove(warren.WarrendPidFile())
+	if cmdSock != nil {
+		cmdSock.Close()
+	}
 }
 
 func main() {
-	warren.RegisterCommand(statusCmd)
+	if checkRunning() {
+		log.Fatal("warrend instance already running")
+	}
 
-	cmdSock, err := net.Listen(warren.CmdSockType(), warren.CmdSockAddr())
-	if cmdSock != nil {
-		defer cmdSock.Close()
-	}
-	if err != nil {
-		log.Fatal("Listen on sock error:", err)
-	}
+	initRunning()
+
+	warren.RegisterCommand(statusCmd)
 
 	// Handle signals
 	c := make(chan os.Signal, 1)
@@ -76,16 +123,18 @@ func main() {
 	)
 	go func() {
 		_ = <-c
-		cmdSock.Close()
+		Shutdown()
 	}()
 
+	// Listen
 	for {
 		fd, err := cmdSock.Accept()
 		fmt.Println("accept")
 		if err != nil {
+			Shutdown()
 			log.Fatal("accpet error:", err)
 		}
 		go sockCmdHandle(fd)
 	}
-
+	Shutdown()
 }

lib/warren/warren.go

@@ -11,7 +11,8 @@ import (
 )
 
 var cmdSockType string = "unix"
-var cmdSockAddr string = "/tmp/warrend.sock"
+var cmdSockAddr string = "/var/run/warrend/warrend.sock"
+var warrendPidFile string = "/var/run/warrend/warrend.pid"
 
 func CmdSockType() string {
 	return cmdSockType
@@ -21,6 +22,10 @@ func CmdSockAddr() string {
 	return cmdSockAddr
 }
 
+func WarrendPidFile() string {
+	return warrendPidFile
+}
+
 func GitHash() string {
 	hash, err := exec.Command("git", "rev-parse", "HEAD").Output()
 	if err != nil {