[#749] morph: Fix panic when closing morph client

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

cmd/frostfs-node/morph.go

@@ -207,6 +207,10 @@ func listenMorphNotifications(ctx context.Context, c *cfg) {
 	})
 	fatalOnErr(err)
 
+	c.onShutdown(func() {
+		lis.Stop()
+	})
+
 	c.workers = append(c.workers, newWorkerFromFunc(func(wCtx context.Context) {
 		runAndLog(wCtx, c, "morph notification", false, func(lCtx context.Context, c *cfg) {
 			lis.ListenWithError(lCtx, c.internalErr)

pkg/morph/client/client.go

@@ -73,6 +73,8 @@ type Client struct {
 
 	// channel for internal stop
 	closeChan chan struct{}
+	closed    atomic.Bool
+	wg        sync.WaitGroup
 
 	// indicates that Client is not able to
 	// establish connection to any of the

pkg/morph/client/multi.go

@@ -75,6 +75,8 @@ func (c *Client) SwitchRPC(ctx context.Context) bool {
 }
 
 func (c *Client) closeWaiter(ctx context.Context) {
+	c.wg.Add(1)
+	defer c.wg.Done()
 	select {
 	case <-ctx.Done():
 	case <-c.closeChan:

pkg/morph/client/notifications.go

@@ -16,8 +16,11 @@ func (c *Client) Close() {
 	// closing should be done via the channel
 	// to prevent switching to another RPC node
 	// in the notification loop
+	if c.closed.CompareAndSwap(false, true) {
 		close(c.closeChan)
 	}
+	c.wg.Wait()
+}
 
 // ReceiveExecutionNotifications performs subscription for notifications
 // generated during contract execution. Events are sent to the specified channel.

pkg/morph/event/listener.go

@@ -96,6 +96,8 @@ type ListenerParams struct {
 type listener struct {
 	mtx sync.RWMutex
 
+	wg sync.WaitGroup
+
 	startOnce, stopOnce sync.Once
 
 	started bool
@@ -124,6 +126,12 @@ var (
 	errNilLogger = errors.New("nil logger")
 
 	errNilSubscriber = errors.New("nil event subscriber")
+
+	errNotificationSubscrConnectionTerminated = errors.New("event subscriber connection has been terminated")
+
+	errNotarySubscrConnectionTerminated = errors.New("notary event subscriber connection has been terminated")
+
+	errBlockNotificationChannelClosed = errors.New("new block notification channel is closed")
 )
 
 // Listen starts the listening for events with registered handlers.
@@ -133,6 +141,8 @@ var (
 // Returns an error if listener was already started.
 func (l *listener) Listen(ctx context.Context) {
 	l.startOnce.Do(func() {
+		l.wg.Add(1)
+		defer l.wg.Done()
 		if err := l.listen(ctx, nil); err != nil {
 			l.log.Error(logs.EventCouldNotStartListenToEvents,
 				zap.String("error", err.Error()),
@@ -149,11 +159,13 @@ func (l *listener) Listen(ctx context.Context) {
 // Returns an error if listener was already started.
 func (l *listener) ListenWithError(ctx context.Context, intError chan<- error) {
 	l.startOnce.Do(func() {
+		l.wg.Add(1)
+		defer l.wg.Done()
 		if err := l.listen(ctx, intError); err != nil {
 			l.log.Error(logs.EventCouldNotStartListenToEvents,
 				zap.String("error", err.Error()),
 			)
-			intError <- err
+			l.sendError(ctx, intError, err)
 		}
 	})
 }
@@ -172,6 +184,8 @@ func (l *listener) listen(ctx context.Context, intError chan<- error) error {
 }
 
 func (l *listener) subscribe(errCh chan error) {
+	l.wg.Add(1)
+	defer l.wg.Done()
 	// create the list of listening contract hashes
 	hashes := make([]util.Uint160, 0)
 
@@ -212,6 +226,23 @@ func (l *listener) subscribe(errCh chan error) {
 	}
 }
 
+func (l *listener) sendError(ctx context.Context, intErr chan<- error, err error) bool {
+	if intErr == nil {
+		return false
+	}
+	// This select required because were are reading from error channel and closing listener
+	// in the same routine when shutting down node.
+	select {
+	case <-ctx.Done():
+		l.log.Info(logs.EventStopEventListenerByContext,
+			zap.String("reason", ctx.Err().Error()),
+		)
+		return false
+	case intErr <- err:
+		return true
+	}
+}
+
 func (l *listener) listenLoop(ctx context.Context, intErr chan<- error, subErrCh chan error) {
 	chs := l.subscriber.NotificationChannels()
 
@@ -219,12 +250,9 @@ loop:
 	for {
 		select {
 		case err := <-subErrCh:
-			if intErr != nil {
-				intErr <- err
-			} else {
+			if !l.sendError(ctx, intErr, err) {
 				l.log.Error(logs.EventStopEventListenerByError, zap.Error(err))
 			}
-
 			break loop
 		case <-ctx.Done():
 			l.log.Info(logs.EventStopEventListenerByContext,
@@ -234,10 +262,7 @@ loop:
 		case notifyEvent, ok := <-chs.NotificationsCh:
 			if !ok {
 				l.log.Warn(logs.EventStopEventListenerByNotificationChannel)
-				if intErr != nil {
-					intErr <- errors.New("event subscriber connection has been terminated")
-				}
-
+				l.sendError(ctx, intErr, errNotificationSubscrConnectionTerminated)
 				break loop
 			} else if notifyEvent == nil {
 				l.log.Warn(logs.EventNilNotificationEventWasCaught)
@@ -248,10 +273,7 @@ loop:
 		case notaryEvent, ok := <-chs.NotaryRequestsCh:
 			if !ok {
 				l.log.Warn(logs.EventStopEventListenerByNotaryChannel)
-				if intErr != nil {
-					intErr <- errors.New("notary event subscriber connection has been terminated")
-				}
-
+				l.sendError(ctx, intErr, errNotarySubscrConnectionTerminated)
 				break loop
 			} else if notaryEvent == nil {
 				l.log.Warn(logs.EventNilNotaryEventWasCaught)
@@ -262,10 +284,7 @@ loop:
 		case b, ok := <-chs.BlockCh:
 			if !ok {
 				l.log.Warn(logs.EventStopEventListenerByBlockChannel)
-				if intErr != nil {
-					intErr <- errors.New("new block notification channel is closed")
-				}
-
+				l.sendError(ctx, intErr, errBlockNotificationChannelClosed)
 				break loop
 			} else if b == nil {
 				l.log.Warn(logs.EventNilBlockWasCaught)
@@ -603,6 +622,7 @@ func (l *listener) Stop() {
 	l.stopOnce.Do(func() {
 		l.subscriber.Close()
 	})
+	l.wg.Wait()
 }
 
 func (l *listener) RegisterBlockHandler(handler BlockHandler) {