core/vidplayer: add useful debug info to http response headers

When viewing HLS manifests/segments, it is often useful to view
information on how those segments were generated. This commit adds
fields such as git-sha and node identifiers to the HTTP response
headers.

core/lpms.go

@@ -56,6 +56,9 @@ type LPMSOpts struct {
 	// on the mux; LPMS won't initialize it.
 	// If set, HttpPort and HttpDisabled are ignored.
 	HttpMux *http.ServeMux
+
+	// Used to tag HTTP headers with useful debug info.
+	HttpDebug    vidplayer.VidPlayerDebug
 }
 
 func defaultLPMSOpts(opts *LPMSOpts) {
@@ -78,7 +81,7 @@ func New(opts *LPMSOpts) *LPMS {
 	if !opts.HttpDisabled && opts.HttpMux == nil {
 		httpAddr = opts.HttpAddr
 	}
-	player := vidplayer.NewVidPlayer(rtmpServer, opts.VodPath, opts.HttpMux)
+	player := vidplayer.NewVidPlayer(rtmpServer, opts.VodPath, opts.HttpMux, opts.HttpDebug)
 	listener := &vidlistener.VidListener{RtmpServer: rtmpServer}
 	return &LPMS{vidPlayer: player, vidListener: listener, workDir: opts.WorkDir, rtmpAddr: opts.RtmpAddr, httpAddr: httpAddr}
 }

segmenter/video_segmenter_test.go

@@ -120,7 +120,7 @@ func TestSegmenter(t *testing.T) {
 	opt := SegmenterOptions{SegLength: time.Second * 4}
 	vs := NewFFMpegVideoSegmenter(workDir, strm.GetStreamID(), strmUrl, opt)
 	server := &rtmp.Server{Addr: ":1939"}
-	player := vidplayer.NewVidPlayer(server, "", nil)
+	player := vidplayer.NewVidPlayer(server, "", nil, nil)
 
 	player.HandleRTMPPlay(
 		func(url *url.URL) (stream.RTMPVideoStream, error) {
@@ -264,7 +264,7 @@ func TestSetStartSeq(t *testing.T) {
 	opt := SegmenterOptions{SegLength: time.Second * 4, StartSeq: startSeq}
 	vs := NewFFMpegVideoSegmenter(workDir, strm.GetStreamID(), strmUrl, opt)
 	server := &rtmp.Server{Addr: ":1936"}
-	player := vidplayer.NewVidPlayer(server, "", nil)
+	player := vidplayer.NewVidPlayer(server, "", nil, nil)
 
 	player.HandleRTMPPlay(
 		func(url *url.URL) (stream.RTMPVideoStream, error) {

vidplayer/player.go

@@ -29,6 +29,16 @@ var ErrRTMP = errors.New("ErrRTMP")
 var ErrHLS = errors.New("ErrHLS")
 var PlaylistWaittime = 6 * time.Second
 
+// vars to tag http response headers w/ debugging info 
+var (
+	lpVersion string 
+)
+
+type VidPlayerDebug struct {
+	DebugEnabled	bool
+	LivepeerVersion string
+}
+
 //VidPlayer is the module that handles playing video. For now we only support RTMP and HLS play.
 type VidPlayer struct {
 	RtmpServer      *joy4rtmp.Server
@@ -40,14 +50,15 @@ type VidPlayer struct {
 func defaultRtmpPlayHandler(url *url.URL) (stream.RTMPVideoStream, error) { return nil, ErrRTMP }
 
 //NewVidPlayer creates a new video player
-func NewVidPlayer(rtmpS *joy4rtmp.Server, vodPath string, mux *http.ServeMux) *VidPlayer {
+func NewVidPlayer(rtmpS *joy4rtmp.Server, vodPath string, mux *http.ServeMux, httpDebugHeaders VidPlayerDebug) *VidPlayer {
 	if mux == nil {
 		mux = http.DefaultServeMux
 	}
 	player := &VidPlayer{RtmpServer: rtmpS, VodPath: vodPath, rtmpPlayHandler: defaultRtmpPlayHandler, mux: mux}
 	if rtmpS != nil {
 		rtmpS.HandlePlay = player.rtmpServerHandlePlay()
 	}
+	player.setDebugHeaders(httpDebugHeaders)
 	return player
 }
 
@@ -97,6 +108,15 @@ func (s *VidPlayer) HandleHLSPlay(
 	})
 }
 
+// Used to set header properties on HTTP responses generated by a B/O/T nodes.
+// This is useful for debugging.
+func (s *VidPlayer) setDebugHeaders(httpDebugHeaders VidPlayerDebug) {
+        if (!httpDebugHeaders.DebugEnabled) {
+		return
+	}
+	lpVersion = httpDebugHeaders.LivepeerVersion
+}
+
 func handleLive(w http.ResponseWriter, r *http.Request,
 	getMasterPlaylist func(url *url.URL) (*m3u8.MasterPlaylist, error),
 	getMediaPlaylist func(url *url.URL) (*m3u8.MediaPlaylist, error),
@@ -107,6 +127,7 @@ func handleLive(w http.ResponseWriter, r *http.Request,
 	w.Header().Set("Access-Control-Allow-Origin", "*")
 	w.Header().Set("Access-Control-Expose-Headers", "Content-Length")
 	w.Header().Set("Cache-Control", "max-age=5")
+	w.Header().Set("Livepeer-Version", lpVersion)
 
 	ext := path.Ext(r.URL.Path)
 	if ".m3u8" == ext {
@@ -220,6 +241,8 @@ func handleVOD(url *url.URL, vodPath string, w http.ResponseWriter) error {
 		w.Write(dat)
 	}
 
+	w.Header().Set("Livepeer-Version", lpVersion)
+
 	http.Error(w, "Cannot find HTTP video resource: "+url.String(), 404)
 	return nil
 }