fix: do not allow lnclient access while it is shutting down (#605)

* fix: do not allow lnclient access while it is shutting down

* fix: also lock the stop endpoint to avoid restart while lnclient is stopping

* chore: fix comment copy

api/api.go

@@ -427,6 +427,12 @@ func (api *api) ChangeUnlockPassword(changeUnlockPasswordRequest *ChangeUnlockPa
 }
 
 func (api *api) Stop() error {
+	if !startMutex.TryLock() {
+		// do not allow to stop twice in case this is somehow called twice
+		return errors.New("app is busy")
+	}
+	defer startMutex.Unlock()
+
 	logger.Logger.Info("Running Stop command")
 	if api.svc.GetLNClient() == nil {
 		return errors.New("LNClient not started")
@@ -719,7 +725,7 @@ func (api *api) Start(startRequest *StartRequest) {
 func (api *api) StartInternal(startRequest *StartRequest) (err error) {
 	if !startMutex.TryLock() {
 		// do not allow to start twice in case this is somehow called twice
-		return errors.New("app is already starting")
+		return errors.New("app is busy")
 	}
 	defer startMutex.Unlock()
 	return api.svc.StartApp(startRequest.UnlockPassword)
@@ -728,7 +734,7 @@ func (api *api) StartInternal(startRequest *StartRequest) (err error) {
 func (api *api) Setup(ctx context.Context, setupRequest *SetupRequest) error {
 	if !startMutex.TryLock() {
 		// do not allow to start twice in case this is somehow called twice
-		return errors.New("app is already starting")
+		return errors.New("app is busy")
 	}
 	defer startMutex.Unlock()
 	info, err := api.GetInfo(ctx)

service/stop.go

@@ -21,8 +21,11 @@ func (svc *service) stopLNClient() {
 	if svc.lnClient == nil {
 		return
 	}
+	lnClient := svc.lnClient
+	svc.lnClient = nil
+
 	logger.Logger.Info("Shutting down LN client")
-	err := svc.lnClient.Shutdown()
+	err := lnClient.Shutdown()
 	if err != nil {
 		logger.Logger.WithError(err).Error("Failed to stop LN client")
 		svc.eventPublisher.Publish(&events.Event{
@@ -34,7 +37,6 @@ func (svc *service) stopLNClient() {
 		return
 	}
 	logger.Logger.Info("Publishing node shutdown event")
-	svc.lnClient = nil
 	svc.eventPublisher.Publish(&events.Event{
 		Event: "nwc_node_stopped",
 	})