graph/db: move Topology client management to ChannelGraph

We plan to later on add an option for a remote graph source which will
be managed from the ChannelGraph. In such a set-up, a node would rely on
the remote graph source for graph updates instead of from gossip sync.
In this scenario, however, our topology subscription logic should still
notify clients of all updates and so it makes more sense to have the
logic as part of the ChannelGraph so that we can send updates we receive
from the remote graph.

graph/builder.go

@@ -109,8 +109,7 @@ type Builder struct {
 	started atomic.Bool
 	stopped atomic.Bool
 
-	ntfnClientCounter atomic.Uint64
-	bestHeight        atomic.Uint32
+	bestHeight atomic.Uint32
 
 	cfg *Config
 
@@ -123,22 +122,6 @@ type Builder struct {
 	// of our currently known best chain are sent over.
 	staleBlocks <-chan *chainview.FilteredBlock
 
-	// topologyUpdates is a channel that carries new topology updates
-	// messages from outside the Builder to be processed by the
-	// networkHandler.
-	topologyUpdates chan any
-
-	// topologyClients maps a client's unique notification ID to a
-	// topologyClient client that contains its notification dispatch
-	// channel.
-	topologyClients *lnutils.SyncMap[uint64, *topologyClient]
-
-	// ntfnClientUpdates is a channel that's used to send new updates to
-	// topology notification clients to the Builder. Updates either
-	// add a new notification client, or cancel notifications for an
-	// existing client.
-	ntfnClientUpdates chan *topologyClientUpdate
-
 	// channelEdgeMtx is a mutex we use to make sure we process only one
 	// ChannelEdgePolicy at a time for a given channelID, to ensure
 	// consistency between the various database accesses.
@@ -163,14 +146,11 @@ var _ ChannelGraphSource = (*Builder)(nil)
 // NewBuilder constructs a new Builder.
 func NewBuilder(cfg *Config) (*Builder, error) {
 	return &Builder{
-		cfg:               cfg,
-		topologyUpdates:   make(chan any),
-		topologyClients:   &lnutils.SyncMap[uint64, *topologyClient]{},
-		ntfnClientUpdates: make(chan *topologyClientUpdate),
-		channelEdgeMtx:    multimutex.NewMutex[uint64](),
-		statTicker:        ticker.New(defaultStatInterval),
-		stats:             new(builderStats),
-		quit:              make(chan struct{}),
+		cfg:            cfg,
+		channelEdgeMtx: multimutex.NewMutex[uint64](),
+		statTicker:     ticker.New(defaultStatInterval),
+		stats:          new(builderStats),
+		quit:           make(chan struct{}),
 	}, nil
 }
 
@@ -656,28 +636,6 @@ func (b *Builder) pruneZombieChans() error {
 	return nil
 }
 
-// handleTopologyUpdate is responsible for sending any topology changes
-// notifications to registered clients.
-//
-// NOTE: must be run inside goroutine.
-func (b *Builder) handleTopologyUpdate(update any) {
-	defer b.wg.Done()
-
-	topChange := &TopologyChange{}
-	err := addToTopologyChange(b.cfg.Graph, topChange, update)
-	if err != nil {
-		log.Errorf("unable to update topology change notification: %v",
-			err)
-		return
-	}
-
-	if topChange.isEmpty() {
-		return
-	}
-
-	b.notifyTopologyChange(topChange)
-}
-
 // networkHandler is the primary goroutine for the Builder. The roles of
 // this goroutine include answering queries related to the state of the
 // network, pruning the graph on new block notification, applying network
@@ -701,16 +659,6 @@ func (b *Builder) networkHandler() {
 		}
 
 		select {
-		// A new fully validated topology update has just arrived.
-		// We'll notify any registered clients.
-		case update := <-b.topologyUpdates:
-			b.wg.Add(1)
-			go b.handleTopologyUpdate(update)
-
-			// TODO(roasbeef): remove all unconnected vertexes
-			// after N blocks pass with no corresponding
-			// announcements.
-
 		case chainUpdate, ok := <-b.staleBlocks:
 			// If the channel has been closed, then this indicates
 			// the daemon is shutting down, so we exit ourselves.
@@ -783,31 +731,6 @@ func (b *Builder) networkHandler() {
 					" processed.", chainUpdate.Height)
 			}
 
-		// A new notification client update has arrived. We're either
-		// gaining a new client, or cancelling notifications for an
-		// existing client.
-		case ntfnUpdate := <-b.ntfnClientUpdates:
-			clientID := ntfnUpdate.clientID
-
-			if ntfnUpdate.cancel {
-				client, ok := b.topologyClients.LoadAndDelete(
-					clientID,
-				)
-				if ok {
-					close(client.exit)
-					client.wg.Wait()
-
-					close(client.ntfnChan)
-				}
-
-				continue
-			}
-
-			b.topologyClients.Store(clientID, &topologyClient{
-				ntfnChan: ntfnUpdate.ntfnChan,
-				exit:     make(chan struct{}),
-			})
-
 		// The graph prune ticker has ticked, so we'll examine the
 		// state of the known graph to filter out any zombie channels
 		// for pruning.
@@ -934,16 +857,6 @@ func (b *Builder) updateGraphWithClosedChannels(
 	log.Infof("Block %v (height=%v) closed %v channels", chainUpdate.Hash,
 		blockHeight, len(chansClosed))
 
-	if len(chansClosed) == 0 {
-		return err
-	}
-
-	// Notify all currently registered clients of the newly closed channels.
-	closeSummaries := createCloseSummaries(blockHeight, chansClosed...)
-	b.notifyTopologyChange(&TopologyChange{
-		ClosedChannels: closeSummaries,
-	})
-
 	return nil
 }
 
@@ -1067,12 +980,6 @@ func (b *Builder) AddNode(node *models.LightningNode,
 		return err
 	}
 
-	select {
-	case b.topologyUpdates <- node:
-	case <-b.quit:
-		return ErrGraphBuilderShuttingDown
-	}
-
 	return nil
 }
 
@@ -1117,12 +1024,6 @@ func (b *Builder) AddEdge(edge *models.ChannelEdgeInfo,
 		return err
 	}
 
-	select {
-	case b.topologyUpdates <- edge:
-	case <-b.quit:
-		return ErrGraphBuilderShuttingDown
-	}
-
 	return nil
 }
 
@@ -1224,12 +1125,6 @@ func (b *Builder) UpdateEdge(update *models.ChannelEdgePolicy,
 		return err
 	}
 
-	select {
-	case b.topologyUpdates <- update:
-	case <-b.quit:
-		return ErrGraphBuilderShuttingDown
-	}
-
 	return nil
 }