itest: remove extra graph topology subscription

lntest/node.go

@@ -1055,50 +1055,12 @@ func (hn *HarnessNode) initLightningClient(conn *grpc.ClientConn) error {
 		return err
 	}
 
-	// Due to a race condition between the ChannelRouter starting and us
-	// making the subscription request, it's possible for our graph
-	// subscription to fail. To ensure we don't start listening for updates
-	// until then, we'll create a dummy subscription to ensure we can do so
-	// successfully before proceeding. We use a dummy subscription in order
-	// to not consume an update from the real one.
-	err := wait.NoError(func() error {
-		req := &lnrpc.GraphTopologySubscription{}
-		ctx, cancelFunc := context.WithCancel(context.Background())
-		topologyClient, err := hn.SubscribeChannelGraph(ctx, req)
-		if err != nil {
-			return err
-		}
-
-		// We'll wait to receive an error back within a one second
-		// timeout. This is needed since creating the client's stream is
-		// independent of the graph subscription being created. The
-		// stream is closed from the server's side upon an error.
-		errChan := make(chan error, 1)
-		go func() {
-			if _, err := topologyClient.Recv(); err != nil {
-				errChan <- err
-			}
-		}()
-
-		select {
-		case err = <-errChan:
-		case <-time.After(time.Second):
-		}
-
-		cancelFunc()
-		return err
-	}, DefaultTimeout)
-	if err != nil {
-		return err
-	}
-
 	// Launch the watcher that will hook into graph related topology change
 	// from the PoV of this node.
 	hn.wg.Add(1)
-	subscribed := make(chan error)
-	go hn.lightningNetworkWatcher(subscribed)
+	go hn.lightningNetworkWatcher()
 
-	return <-subscribed
+	return nil
 }
 
 // FetchNodeInfo queries an unlocked node to retrieve its public key.
@@ -1394,40 +1356,19 @@ func checkChanPointInGraph(ctx context.Context,
 // closed or opened within the network. In order to dispatch these
 // notifications, the GraphTopologySubscription client exposed as part of the
 // gRPC interface is used.
-func (hn *HarnessNode) lightningNetworkWatcher(subscribed chan error) {
+func (hn *HarnessNode) lightningNetworkWatcher() {
 	defer hn.wg.Done()
 
 	graphUpdates := make(chan *lnrpc.GraphTopologyUpdate)
+
+	// Start a goroutine to receive graph updates.
 	hn.wg.Add(1)
 	go func() {
 		defer hn.wg.Done()
-
-		req := &lnrpc.GraphTopologySubscription{}
-		ctx, cancelFunc := context.WithCancel(context.Background())
-		defer cancelFunc()
-		topologyClient, err := hn.SubscribeChannelGraph(ctx, req)
+		err := hn.receiveTopologyClientStream(graphUpdates)
 		if err != nil {
-			msg := fmt.Sprintf("%s(%d): unable to create topology "+
-				"client: %v (%s)", hn.Name(), hn.NodeID, err,
-				time.Now().String())
-			subscribed <- fmt.Errorf(msg)
-			return
-		}
-		close(subscribed)
-
-		for {
-			update, err := topologyClient.Recv()
-			if err == io.EOF {
-				return
-			} else if err != nil {
-				return
-			}
-
-			select {
-			case graphUpdates <- update:
-			case <-hn.quit:
-				return
-			}
+			hn.PrintErr("receive topology client stream "+
+				"got err:%v", err)
 		}
 	}()
 
@@ -1713,3 +1654,90 @@ func (hn *HarnessNode) handleCloseChannelWatchRequest(req *chanWatchRequest) {
 		req.eventChan,
 	)
 }
+
+type topologyClient lnrpc.Lightning_SubscribeChannelGraphClient
+
+// newTopologyClient creates a topology client.
+func (hn *HarnessNode) newTopologyClient(
+	ctx context.Context) (topologyClient, error) {
+
+	req := &lnrpc.GraphTopologySubscription{}
+	client, err := hn.SubscribeChannelGraph(ctx, req)
+	if err != nil {
+		return nil, fmt.Errorf("%s(%d): unable to create topology "+
+			"client: %v (%s)", hn.Name(), hn.NodeID, err,
+			time.Now().String())
+	}
+
+	return client, nil
+}
+
+// receiveTopologyClientStream initializes a topologyClient to subscribe
+// topology update events. Due to a race condition between the ChannelRouter
+// starting and us making the subscription request, it's possible for our graph
+// subscription to fail. In that case, we will retry the subscription until it
+// succeeds or fail after 10 seconds.
+//
+// NOTE: must be run as a goroutine.
+func (hn *HarnessNode) receiveTopologyClientStream(
+	receiver chan *lnrpc.GraphTopologyUpdate) error {
+
+	ctxb := context.Background()
+
+	// Create a topology client to receive graph updates.
+	client, err := hn.newTopologyClient(ctxb)
+	if err != nil {
+		return fmt.Errorf("create topologyClient failed: %v", err)
+	}
+
+	// We use the context to time out when retrying graph subscription.
+	ctxt, cancel := context.WithTimeout(ctxb, DefaultTimeout)
+	defer cancel()
+
+	for {
+		update, err := client.Recv()
+
+		switch {
+		case err == nil:
+			// Good case. We will send the update to the receiver.
+
+		case strings.Contains(err.Error(), "router not started"):
+			// If the router hasn't been started, we will retry
+			// every 200 ms until it has been started or fail
+			// after the ctxt is timed out.
+			select {
+			case <-ctxt.Done():
+				return fmt.Errorf("graph subscription: " +
+					"router not started before timeout")
+			case <-time.After(wait.PollInterval):
+			case <-hn.quit:
+				return nil
+			}
+
+			// Re-create the topology client.
+			client, err = hn.newTopologyClient(ctxb)
+			if err != nil {
+				return fmt.Errorf("create topologyClient "+
+					"failed: %v", err)
+			}
+
+			continue
+
+		case strings.Contains(err.Error(), "EOF"):
+			// End of subscription stream. Do nothing and quit.
+			return nil
+
+		default:
+			// An expected error is returned, return and leave it
+			// to be handled by the caller.
+			return fmt.Errorf("graph subscription err: %v", err)
+		}
+
+		// Send the update or quit.
+		select {
+		case receiver <- update:
+		case <-hn.quit:
+			return nil
+		}
+	}
+}

lntest/wait/wait.go

@@ -5,17 +5,18 @@ import (
 	"time"
 )
 
+// PollInterval is a constant specifying a 200 ms interval.
+const PollInterval = 200 * time.Millisecond
+
 // Predicate is a helper test function that will wait for a timeout period of
 // time until the passed predicate returns true. This function is helpful as
 // timing doesn't always line up well when running integration tests with
 // several running lnd nodes. This function gives callers a way to assert that
 // some property is upheld within a particular time frame.
 func Predicate(pred func() bool, timeout time.Duration) error {
-	const pollInterval = 200 * time.Millisecond
-
 	exitTimer := time.After(timeout)
 	for {
-		<-time.After(pollInterval)
+		<-time.After(PollInterval)
 
 		select {
 		case <-exitTimer: