Fix API event subscription

The API never got the first few events ("Starting" etc) as it subscribed
too late. Instead, set up a subscription for it early on. If the API is
configured not to run this is unnecessary but doesn't hurt very much.

cmd/syncthing/gui.go

@@ -49,7 +49,6 @@ var (
 	guiErrors    = []guiError{}
 	guiErrorsMut = sync.NewMutex()
 	startTime    = time.Now()
-	eventSub     *events.BufferedSubscription
 )
 
 type apiSvc struct {
@@ -60,14 +59,16 @@ type apiSvc struct {
 	fss             *folderSummarySvc
 	stop            chan struct{}
 	systemConfigMut sync.Mutex
+	eventSub        *events.BufferedSubscription
 }
 
-func newAPISvc(cfg config.GUIConfiguration, assetDir string, m *model.Model) (*apiSvc, error) {
+func newAPISvc(cfg config.GUIConfiguration, assetDir string, m *model.Model, eventSub *events.BufferedSubscription) (*apiSvc, error) {
 	svc := &apiSvc{
 		cfg:             cfg,
 		assetDir:        assetDir,
 		model:           m,
 		systemConfigMut: sync.NewMutex(),
+		eventSub:        eventSub,
 	}
 
 	var err error
@@ -125,9 +126,6 @@ func (s *apiSvc) Serve() {
 	s.stop = make(chan struct{})
 
 	l.AddHandler(logger.LevelWarn, s.showGuiError)
-	sub := events.Default.Subscribe(events.AllEvents)
-	eventSub = events.NewBufferedSubscription(sub, 1000)
-	defer events.Default.Unsubscribe(sub)
 
 	// The GET handlers
 	getRestMux := http.NewServeMux()
@@ -743,7 +741,7 @@ func (s *apiSvc) getEvents(w http.ResponseWriter, r *http.Request) {
 	f := w.(http.Flusher)
 	f.Flush()
 
-	evs := eventSub.Since(since, nil)
+	evs := s.eventSub.Since(since, nil)
 	if 0 < limit && limit < len(evs) {
 		evs = evs[len(evs)-limit:]
 	}

cmd/syncthing/main.go

@@ -447,6 +447,9 @@ func syncthingMain() {
 		mainSvc.Add(newVerboseSvc())
 	}
 
+	// Event subscription for the API; must start early to catch the early events.
+	apiSub := events.NewBufferedSubscription(events.Default.Subscribe(events.AllEvents), 1000)
+
 	if len(os.Getenv("GOMAXPROCS")) == 0 {
 		runtime.GOMAXPROCS(runtime.NumCPU())
 	}
@@ -628,7 +631,7 @@ func syncthingMain() {
 
 	// GUI
 
-	setupGUI(mainSvc, cfg, m)
+	setupGUI(mainSvc, cfg, m, apiSub)
 
 	// The default port we announce, possibly modified by setupUPnP next.
 
@@ -768,7 +771,7 @@ func startAuditing(mainSvc *suture.Supervisor) {
 	l.Infoln("Audit log in", auditFile)
 }
 
-func setupGUI(mainSvc *suture.Supervisor, cfg *config.Wrapper, m *model.Model) {
+func setupGUI(mainSvc *suture.Supervisor, cfg *config.Wrapper, m *model.Model, apiSub *events.BufferedSubscription) {
 	opts := cfg.Options()
 	guiCfg := overrideGUIConfig(cfg.GUI(), guiAddress, guiAuthentication, guiAPIKey)
 
@@ -797,7 +800,7 @@ func setupGUI(mainSvc *suture.Supervisor, cfg *config.Wrapper, m *model.Model) {
 
 			urlShow := fmt.Sprintf("%s://%s/", proto, net.JoinHostPort(hostShow, strconv.Itoa(addr.Port)))
 			l.Infoln("Starting web GUI on", urlShow)
-			api, err := newAPISvc(guiCfg, guiAssets, m)
+			api, err := newAPISvc(guiCfg, guiAssets, m, apiSub)
 			if err != nil {
 				l.Fatalln("Cannot start GUI:", err)
 			}