From c923c728751cfd34a6018c6cd805f17750b90663 Mon Sep 17 00:00:00 2001
From: Christian Pointner <equinox@helsinki.at>
Date: Fri, 24 Mar 2017 18:50:02 +0100
Subject: added system socket activation


diff --git a/Makefile b/Makefile
index 2ccf0c9..337e9a7 100644
--- a/Makefile
+++ b/Makefile
@@ -28,7 +28,8 @@ GOCMD := GOPATH=$(curdir) go
 
 EXECUTEABLE := rhrdtime
 
-LIBS := "github.com/gorilla/websocket"
+LIBS := "github.com/gorilla/websocket" \
+        "github.com/coreos/go-systemd/activation"
 
 
 .PHONY: getlibs updatelibs vet format build clean distclean
diff --git a/debian/rhrdtime.service b/debian/rhrdtime.service
index 0d4658e..af54634 100644
--- a/debian/rhrdtime.service
+++ b/debian/rhrdtime.service
@@ -1,14 +1,12 @@
 [Unit]
 Description=Radio Helsinki Rivendell Time Websocket Server
+After=local-fs.target
 
 [Service]
 User=rhrdtime
 Group=rhrdtime
+Type=simple
 ExecStart=/usr/bin/rhrdtime
-Restart=always
-RestartSec=1s
-StartLimitInterval=5
-StartLimitBurst=6
 PrivateTmp=yes
 PrivateDevices=yes
 ProtectSystem=full
diff --git a/debian/rhrdtime.socket b/debian/rhrdtime.socket
new file mode 100644
index 0000000..6718aa7
--- /dev/null
+++ b/debian/rhrdtime.socket
@@ -0,0 +1,9 @@
+[Unit]
+Description=Radio Helsinki Rivendell Time Websocket Server
+
+[Socket]
+ListenStream=127.0.0.1:3000
+ListenStream=[::1]:3000
+
+[Install]
+WantedBy=sockets.target
diff --git a/src/rhrdtime/rhrdtime.go b/src/rhrdtime/rhrdtime.go
index 4bdf680..d4d24b3 100644
--- a/src/rhrdtime/rhrdtime.go
+++ b/src/rhrdtime/rhrdtime.go
@@ -28,10 +28,13 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
+	"net"
 	"net/http"
-	_ "net/http/pprof"
+	"os"
+	"sync"
 	"time"
 
+	"github.com/coreos/go-systemd/activation"
 	"github.com/gorilla/websocket"
 )
 
@@ -63,9 +66,11 @@ type ntpMessage struct {
 func handleNTPClient(w http.ResponseWriter, r *http.Request) {
 	ws, err := websocket.Upgrade(w, r, nil, 1024, 1024)
 	if _, ok := err.(websocket.HandshakeError); ok {
+		fmt.Println("Invalid request from", r.RemoteAddr)
 		http.Error(w, "Not a websocket handshake", 400)
 		return
 	} else if err != nil {
+		fmt.Println("Invalid request from", r.RemoteAddr)
 		fmt.Println(err)
 		return
 	}
@@ -82,7 +87,7 @@ func handleNTPClient(w http.ResponseWriter, r *http.Request) {
 
 			var n ntpMessage
 			if err := json.Unmarshal(msg, &n); err != nil {
-				fmt.Println("Ignoring malformed (", err, ") NTP message from:", ws.RemoteAddr())
+				fmt.Println("Ignoring malformed (", err, ") NTP message from", ws.RemoteAddr())
 				continue
 			}
 
@@ -106,7 +111,7 @@ func handleNTPClient(w http.ResponseWriter, r *http.Request) {
 }
 
 func main() {
-	addr_s := flag.String("addr", ":3000", "addr:port to listen on, default: ':3000'")
+	addr := flag.String("addr", "", "addr:port to listen on, default: use systemd socket activation or ':3000' when no sockets are passed")
 	help := flag.Bool("help", false, "show usage")
 
 	flag.Parse()
@@ -115,7 +120,43 @@ func main() {
 		return
 	}
 
-	http.HandleFunc("/ntp", handleNTPClient)
+	var listeners []net.Listener
+	if *addr == "" {
+		lns, err := activation.Listeners(true)
+		if err != nil {
+			fmt.Println("error while getting socket from systemd:", err)
+			os.Exit(1)
+		}
+		listeners = lns
+	}
 
-	http.ListenAndServe(*addr_s, nil)
+	if len(listeners) == 0 {
+		if *addr == "" {
+			*addr = ":3000"
+		}
+		ln, err := net.Listen("tcp", *addr)
+		if err != nil {
+			fmt.Println("error listening on socket:", err)
+			os.Exit(1)
+		}
+		listeners = append(listeners, ln)
+	}
+
+	for _, ln := range listeners {
+		fmt.Println("listening on:", ln.Addr().String())
+	}
+
+	var wg sync.WaitGroup
+	for _, l := range listeners {
+		ln := l
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			mux := http.NewServeMux()
+			mux.HandleFunc("/ntp", handleNTPClient)
+			server := &http.Server{Handler: mux, ReadTimeout: 12 * time.Hour, WriteTimeout: 12 * time.Hour}
+			server.Serve(ln)
+		}()
+	}
+	wg.Wait()
 }
-- 
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