routing+routerrpc: test stream cancellation

Test stream cancellation of the TrackPayments rpc call. In order to achieve
this, ControlTowerSubscriber is converted to an interface, to avoid trying to
close a null channel when closing the subscription. By returning a mock
implementation of the ControlTowerSubscriber in the test that problem is
avoided.

lnrpc/routerrpc/router_server.go

@@ -791,7 +791,7 @@ func (s *Server) TrackPayments(request *TrackPaymentsRequest,
 
 // trackPaymentStream streams payment updates to the client.
 func (s *Server) trackPaymentStream(context context.Context,
-	subscription *routing.ControlTowerSubscriber, noInflightUpdates bool,
+	subscription routing.ControlTowerSubscriber, noInflightUpdates bool,
 	send func(*lnrpc.Payment) error) error {
 
 	defer subscription.Close()
@@ -799,7 +799,7 @@ func (s *Server) trackPaymentStream(context context.Context,
 	// Stream updates back to the client.
 	for {
 		select {
-		case item, ok := <-subscription.Updates:
+		case item, ok := <-subscription.Updates():
 			if !ok {
 				// No more payment updates.
 				return nil

lnrpc/routerrpc/router_server_test.go

@@ -13,21 +13,46 @@ import (
 	"google.golang.org/grpc"
 )
 
-func makeStreamMock() *StreamMock {
-	return &StreamMock{
-		ctx:            context.Background(),
-		sentFromServer: make(chan *lnrpc.Payment, 10),
-	}
-}
-
-type StreamMock struct {
+type streamMock struct {
 	grpc.ServerStream
 	ctx            context.Context
 	sentFromServer chan *lnrpc.Payment
 }
 
-func makeControlTowerMock() *ControlTowerMock {
-	towerMock := &ControlTowerMock{
+func makeStreamMock(ctx context.Context) *streamMock {
+	return &streamMock{
+		ctx:            ctx,
+		sentFromServer: make(chan *lnrpc.Payment, 10),
+	}
+}
+
+func (m *streamMock) Context() context.Context {
+	return m.ctx
+}
+
+func (m *streamMock) Send(p *lnrpc.Payment) error {
+	m.sentFromServer <- p
+	return nil
+}
+
+type controlTowerSubscriberMock struct {
+	updates <-chan interface{}
+}
+
+func (s controlTowerSubscriberMock) Updates() <-chan interface{} {
+	return s.updates
+}
+
+func (s controlTowerSubscriberMock) Close() {
+}
+
+type controlTowerMock struct {
+	queue *queue.ConcurrentQueue
+	routing.ControlTower
+}
+
+func makeControlTowerMock() *controlTowerMock {
+	towerMock := &controlTowerMock{
 		queue: queue.NewConcurrentQueue(20),
 	}
 	towerMock.queue.Start()
@@ -35,26 +60,40 @@ func makeControlTowerMock() *ControlTowerMock {
 	return towerMock
 }
 
-type ControlTowerMock struct {
-	queue *queue.ConcurrentQueue
-	routing.ControlTower
-}
+func (t *controlTowerMock) SubscribeAllPayments() (
+	routing.ControlTowerSubscriber, error) {
 
-func (t *ControlTowerMock) SubscribeAllPayments() (
-	*routing.ControlTowerSubscriber, error) {
-
-	return &routing.ControlTowerSubscriber{
-		Updates: t.queue.ChanOut(),
+	return &controlTowerSubscriberMock{
+		updates: t.queue.ChanOut(),
 	}, nil
 }
 
-func (m *StreamMock) Context() context.Context {
-	return m.ctx
-}
+// TestTrackPaymentsReturnsOnCancelContext tests whether TrackPayments returns
+// when the stream context is cancelled.
+func TestTrackPaymentsReturnsOnCancelContext(t *testing.T) {
+	// Setup mocks and request.
+	request := &TrackPaymentsRequest{
+		NoInflightUpdates: false,
+	}
+	towerMock := makeControlTowerMock()
 
-func (m *StreamMock) Send(p *lnrpc.Payment) error {
-	m.sentFromServer <- p
-	return nil
+	streamCtx, cancelStream := context.WithCancel(context.Background())
+	stream := makeStreamMock(streamCtx)
+
+	server := &Server{
+		cfg: &Config{
+			RouterBackend: &RouterBackend{
+				Tower: towerMock,
+			},
+		},
+	}
+
+	// Cancel stream immediately
+	cancelStream()
+
+	// Make sure the call returns.
+	err := server.TrackPayments(request, stream)
+	require.Equal(t, context.Canceled, err)
 }
 
 // TestTrackPaymentsInflightUpdate tests whether all updates from the control
@@ -65,7 +104,11 @@ func TestTrackPaymentsInflightUpdates(t *testing.T) {
 		NoInflightUpdates: false,
 	}
 	towerMock := makeControlTowerMock()
-	stream := makeStreamMock()
+
+	streamCtx, cancelStream := context.WithCancel(context.Background())
+	stream := makeStreamMock(streamCtx)
+	defer cancelStream()
+
 	server := &Server{
 		cfg: &Config{
 			RouterBackend: &RouterBackend{
@@ -77,7 +120,7 @@ func TestTrackPaymentsInflightUpdates(t *testing.T) {
 	// Listen to payment updates in a goroutine.
 	go func() {
 		err := server.TrackPayments(request, stream)
-		require.NoError(t, err)
+		require.Equal(t, context.Canceled, err)
 	}()
 
 	// Enqueue some payment updates on the mock.
@@ -119,11 +162,15 @@ func TestTrackPaymentsNoInflightUpdates(t *testing.T) {
 	request := &TrackPaymentsRequest{
 		NoInflightUpdates: true,
 	}
-	towerMock := &ControlTowerMock{
+	towerMock := &controlTowerMock{
 		queue: queue.NewConcurrentQueue(20),
 	}
 	towerMock.queue.Start()
-	stream := makeStreamMock()
+
+	streamCtx, cancelStream := context.WithCancel(context.Background())
+	stream := makeStreamMock(streamCtx)
+	defer cancelStream()
+
 	server := &Server{
 		cfg: &Config{
 			RouterBackend: &RouterBackend{
@@ -135,7 +182,7 @@ func TestTrackPaymentsNoInflightUpdates(t *testing.T) {
 	// Listen to payment updates in a goroutine.
 	go func() {
 		err := server.TrackPayments(request, stream)
-		require.NoError(t, err)
+		require.Equal(t, context.Canceled, err)
 	}()
 
 	// Enqueue some payment updates on the mock.

routing/control_tower.go

@@ -60,40 +60,48 @@ type ControlTower interface {
 	// SubscribePayment subscribes to updates for the payment with the given
 	// hash. A first update with the current state of the payment is always
 	// sent out immediately.
-	SubscribePayment(paymentHash lntypes.Hash) (*ControlTowerSubscriber,
+	SubscribePayment(paymentHash lntypes.Hash) (ControlTowerSubscriber,
 		error)
 
 	// SubscribeAllPayments subscribes to updates for all payments. A first
 	// update with the current state of every inflight payment is always
 	// sent out immediately.
-	SubscribeAllPayments() (*ControlTowerSubscriber, error)
+	SubscribeAllPayments() (ControlTowerSubscriber, error)
 }
 
 // ControlTowerSubscriber contains the state for a payment update subscriber.
-type ControlTowerSubscriber struct {
+type ControlTowerSubscriber interface {
 	// Updates is the channel over which *channeldb.MPPayment updates can be
 	// received.
-	Updates <-chan interface{}
+	Updates() <-chan interface{}
 
-	queue *queue.ConcurrentQueue
-	quit  chan struct{}
+	// Close signals that the subscriber is no longer interested in updates.
+	Close()
+}
+
+// ControlTowerSubscriberImpl contains the state for a payment update
+// subscriber.
+type controlTowerSubscriberImpl struct {
+	updates <-chan interface{}
+	queue   *queue.ConcurrentQueue
+	quit    chan struct{}
 }
 
 // newControlTowerSubscriber instantiates a new subscriber state object.
-func newControlTowerSubscriber() *ControlTowerSubscriber {
+func newControlTowerSubscriber() *controlTowerSubscriberImpl {
 	// Create a queue for payment updates.
 	queue := queue.NewConcurrentQueue(20)
 	queue.Start()
 
-	return &ControlTowerSubscriber{
-		Updates: queue.ChanOut(),
+	return &controlTowerSubscriberImpl{
+		updates: queue.ChanOut(),
 		queue:   queue,
 		quit:    make(chan struct{}),
 	}
 }
 
 // Close signals that the subscriber is no longer interested in updates.
-func (s *ControlTowerSubscriber) Close() {
+func (s *controlTowerSubscriberImpl) Close() {
 	// Close quit channel so that any pending writes to the queue are
 	// cancelled.
 	close(s.quit)
@@ -102,6 +110,12 @@ func (s *ControlTowerSubscriber) Close() {
 	s.queue.Stop()
 }
 
+// Updates is the channel over which *channeldb.MPPayment updates can be
+// received.
+func (s *controlTowerSubscriberImpl) Updates() <-chan interface{} {
+	return s.updates
+}
+
 // controlTower is persistent implementation of ControlTower to restrict
 // double payment sending.
 type controlTower struct {
@@ -111,8 +125,8 @@ type controlTower struct {
 	// to all payments. This is used to easily remove the subscriber when
 	// necessary.
 	subscriberIndex        uint64
-	subscribersAllPayments map[uint64]*ControlTowerSubscriber
-	subscribers            map[lntypes.Hash][]*ControlTowerSubscriber
+	subscribersAllPayments map[uint64]*controlTowerSubscriberImpl
+	subscribers            map[lntypes.Hash][]*controlTowerSubscriberImpl
 	subscribersMtx         sync.Mutex
 
 	// paymentsMtx provides synchronization on the payment level to ensure
@@ -126,9 +140,9 @@ func NewControlTower(db *channeldb.PaymentControl) ControlTower {
 	return &controlTower{
 		db: db,
 		subscribersAllPayments: make(
-			map[uint64]*ControlTowerSubscriber,
+			map[uint64]*controlTowerSubscriberImpl,
 		),
-		subscribers: make(map[lntypes.Hash][]*ControlTowerSubscriber),
+		subscribers: make(map[lntypes.Hash][]*controlTowerSubscriberImpl),
 		paymentsMtx: multimutex.NewHashMutex(),
 	}
 }
@@ -245,7 +259,7 @@ func (p *controlTower) FetchInFlightPayments() ([]*channeldb.MPPayment, error) {
 // first update with the current state of the payment is always sent out
 // immediately.
 func (p *controlTower) SubscribePayment(paymentHash lntypes.Hash) (
-	*ControlTowerSubscriber, error) {
+	ControlTowerSubscriber, error) {
 
 	// Take lock before querying the db to prevent missing or duplicating an
 	// update.
@@ -286,7 +300,7 @@ func (p *controlTower) SubscribePayment(paymentHash lntypes.Hash) (
 // of the payment stream could produce out-of-order and/or duplicate events. In
 // order to get updates for every in-flight payment attempt make sure to
 // subscribe to this method before initiating any payments.
-func (p *controlTower) SubscribeAllPayments() (*ControlTowerSubscriber, error) {
+func (p *controlTower) SubscribeAllPayments() (ControlTowerSubscriber, error) {
 	subscriber := newControlTowerSubscriber()
 
 	// Add the subscriber to the list before fetching in-flight payments, so
@@ -337,7 +351,7 @@ func (p *controlTower) notifySubscribers(paymentHash lntypes.Hash,
 
 	// Copy subscribers to all payments locally while holding the lock in
 	// order to avoid concurrency issues while reading/writing the map.
-	subscribersAllPayments := make(map[uint64]*ControlTowerSubscriber)
+	subscribersAllPayments := make(map[uint64]*controlTowerSubscriberImpl)
 	for k, v := range p.subscribersAllPayments {
 		subscribersAllPayments[k] = v
 	}

routing/control_tower_test.go

@@ -115,7 +115,7 @@ func TestControlTowerSubscribeSuccess(t *testing.T) {
 
 	// We expect all subscribers to now report the final outcome followed by
 	// no other events.
-	subscribers := []*ControlTowerSubscriber{
+	subscribers := []ControlTowerSubscriber{
 		subscriber1, subscriber2, subscriber3,
 	}
 
@@ -123,7 +123,7 @@ func TestControlTowerSubscribeSuccess(t *testing.T) {
 		var result *channeldb.MPPayment
 		for result == nil || result.Status == channeldb.StatusInFlight {
 			select {
-			case item := <-s.Updates:
+			case item := <-s.Updates():
 				result = item.(*channeldb.MPPayment)
 			case <-time.After(testTimeout):
 				t.Fatal("timeout waiting for payment result")
@@ -149,7 +149,7 @@ func TestControlTowerSubscribeSuccess(t *testing.T) {
 
 		// After the final event, we expect the channel to be closed.
 		select {
-		case _, ok := <-s.Updates:
+		case _, ok := <-s.Updates():
 			if ok {
 				t.Fatal("expected channel to be closed")
 			}
@@ -248,7 +248,7 @@ func TestPaymentControlSubscribeAllSuccess(t *testing.T) {
 	// After exactly 5 updates both payments will/should have completed.
 	for i := 0; i < 5; i++ {
 		select {
-		case item := <-subscription.Updates:
+		case item := <-subscription.Updates():
 			id := item.(*channeldb.MPPayment).Info.PaymentIdentifier
 			results[id] = item.(*channeldb.MPPayment)
 		case <-time.After(testTimeout):
@@ -320,13 +320,13 @@ func TestPaymentControlSubscribeAllImmediate(t *testing.T) {
 
 	// Assert the new subscription receives the old update.
 	select {
-	case update := <-subscription.Updates:
+	case update := <-subscription.Updates():
 		require.NotNil(t, update)
 		require.Equal(
 			t, info.PaymentIdentifier,
 			update.(*channeldb.MPPayment).Info.PaymentIdentifier,
 		)
-		require.Len(t, subscription.Updates, 0)
+		require.Len(t, subscription.Updates(), 0)
 	case <-time.After(testTimeout):
 		require.Fail(t, "timeout waiting for payment result")
 	}
@@ -361,14 +361,14 @@ func TestPaymentControlUnsubscribeSuccess(t *testing.T) {
 
 	// Assert all subscriptions receive the update.
 	select {
-	case update1 := <-subscription1.Updates:
+	case update1 := <-subscription1.Updates():
 		require.NotNil(t, update1)
 	case <-time.After(testTimeout):
 		require.Fail(t, "timeout waiting for payment result")
 	}
 
 	select {
-	case update2 := <-subscription2.Updates:
+	case update2 := <-subscription2.Updates():
 		require.NotNil(t, update2)
 	case <-time.After(testTimeout):
 		require.Fail(t, "timeout waiting for payment result")
@@ -388,13 +388,13 @@ func TestPaymentControlUnsubscribeSuccess(t *testing.T) {
 
 	// Assert only subscription 2 receives the update.
 	select {
-	case update2 := <-subscription2.Updates:
+	case update2 := <-subscription2.Updates():
 		require.NotNil(t, update2)
 	case <-time.After(testTimeout):
 		require.Fail(t, "timeout waiting for payment result")
 	}
 
-	require.Len(t, subscription1.Updates, 0)
+	require.Len(t, subscription1.Updates(), 0)
 
 	// Close the second subscription.
 	subscription2.Close()
@@ -404,8 +404,8 @@ func TestPaymentControlUnsubscribeSuccess(t *testing.T) {
 	require.NoError(t, err)
 
 	// Assert no subscriptions receive the update.
-	require.Len(t, subscription1.Updates, 0)
-	require.Len(t, subscription2.Updates, 0)
+	require.Len(t, subscription1.Updates(), 0)
+	require.Len(t, subscription2.Updates(), 0)
 }
 
 func testPaymentControlSubscribeFail(t *testing.T, registerAttempt,
@@ -467,7 +467,7 @@ func testPaymentControlSubscribeFail(t *testing.T, registerAttempt,
 
 	// We expect both subscribers to now report the final outcome followed
 	// by no other events.
-	subscribers := []*ControlTowerSubscriber{
+	subscribers := []ControlTowerSubscriber{
 		subscriber1, subscriber2,
 	}
 
@@ -475,7 +475,7 @@ func testPaymentControlSubscribeFail(t *testing.T, registerAttempt,
 		var result *channeldb.MPPayment
 		for result == nil || result.Status == channeldb.StatusInFlight {
 			select {
-			case item := <-s.Updates:
+			case item := <-s.Updates():
 				result = item.(*channeldb.MPPayment)
 			case <-time.After(testTimeout):
 				t.Fatal("timeout waiting for payment result")
@@ -513,7 +513,7 @@ func testPaymentControlSubscribeFail(t *testing.T, registerAttempt,
 
 		// After the final event, we expect the channel to be closed.
 		select {
-		case _, ok := <-s.Updates:
+		case _, ok := <-s.Updates():
 			if ok {
 				t.Fatal("expected channel to be closed")
 			}

routing/mock_test.go

@@ -552,13 +552,13 @@ func (m *mockControlTowerOld) FetchInFlightPayments() (
 }
 
 func (m *mockControlTowerOld) SubscribePayment(paymentHash lntypes.Hash) (
-	*ControlTowerSubscriber, error) {
+	ControlTowerSubscriber, error) {
 
 	return nil, errors.New("not implemented")
 }
 
 func (m *mockControlTowerOld) SubscribeAllPayments() (
-	*ControlTowerSubscriber, error) {
+	ControlTowerSubscriber, error) {
 
 	return nil, errors.New("not implemented")
 }
@@ -774,17 +774,17 @@ func (m *mockControlTower) FetchInFlightPayments() (
 }
 
 func (m *mockControlTower) SubscribePayment(paymentHash lntypes.Hash) (
-	*ControlTowerSubscriber, error) {
+	ControlTowerSubscriber, error) {
 
 	args := m.Called(paymentHash)
-	return args.Get(0).(*ControlTowerSubscriber), args.Error(1)
+	return args.Get(0).(ControlTowerSubscriber), args.Error(1)
 }
 
 func (m *mockControlTower) SubscribeAllPayments() (
-	*ControlTowerSubscriber, error) {
+	ControlTowerSubscriber, error) {
 
 	args := m.Called()
-	return args.Get(0).(*ControlTowerSubscriber), args.Error(1)
+	return args.Get(0).(ControlTowerSubscriber), args.Error(1)
 }
 
 type mockLink struct {