routing: remove the mutex and use SyncMap instead

This commit removes the lock used to protect the map `topologyClients`
and replace the map with a `SyncMap`.

routing/notifications.go

@@ -10,7 +10,6 @@ import (
 	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/btcsuite/btcd/wire"
-	"github.com/davecgh/go-spew/spew"
 	"github.com/go-errors/errors"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -117,23 +116,19 @@ type topologyClient struct {
 // notifyTopologyChange notifies all registered clients of a new change in
 // graph topology in a non-blocking.
 func (r *ChannelRouter) notifyTopologyChange(topologyDiff *TopologyChange) {
-	r.RLock()
-	defer r.RUnlock()
 
-	numClients := len(r.topologyClients)
-	if numClients == 0 {
-		return
-	}
-
-	log.Tracef("Sending topology notification to %v clients %v",
-		numClients, newLogClosure(func() string {
-			return spew.Sdump(topologyDiff)
-		}),
-	)
-
-	for _, client := range r.topologyClients {
+	// notifyClient is a helper closure that will send topology updates to
+	// the given client.
+	notifyClient := func(clientID uint64, client *topologyClient) bool {
 		client.wg.Add(1)
 
+		log.Tracef("Sending topology notification to client=%v, "+
+			"NodeUpdates=%v, ChannelEdgeUpdates=%v, "+
+			"ClosedChannels=%v", clientID,
+			len(topologyDiff.NodeUpdates),
+			len(topologyDiff.ChannelEdgeUpdates),
+			len(topologyDiff.ClosedChannels))
+
 		go func(c *topologyClient) {
 			defer c.wg.Done()
 
@@ -153,7 +148,15 @@ func (r *ChannelRouter) notifyTopologyChange(topologyDiff *TopologyChange) {
 
 			}
 		}(client)
+
+		// Always return true here so the following Range will iterate
+		// all clients.
+		return true
 	}
+
+	// Range over the set of active clients, and attempt to send the
+	// topology updates.
+	r.topologyClients.Range(notifyClient)
 }
 
 // TopologyChange represents a new set of modifications to the channel graph.

routing/router.go

@@ -25,6 +25,7 @@ import (
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lntypes"
+	"github.com/lightningnetwork/lnd/lnutils"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/btcwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chanvalidate"
@@ -425,7 +426,7 @@ type ChannelRouter struct {
 	// topologyClients maps a client's unique notification ID to a
 	// topologyClient client that contains its notification dispatch
 	// channel.
-	topologyClients map[uint64]*topologyClient
+	topologyClients *lnutils.SyncMap[uint64, *topologyClient]
 
 	// ntfnClientUpdates is a channel that's used to send new updates to
 	// topology notification clients to the ChannelRouter. Updates either
@@ -446,8 +447,6 @@ type ChannelRouter struct {
 	// announcements over a window of defaultStatInterval.
 	stats *routerStats
 
-	sync.RWMutex
-
 	quit chan struct{}
 	wg   sync.WaitGroup
 }
@@ -474,7 +473,7 @@ func New(cfg Config) (*ChannelRouter, error) {
 			source: selfNode.PubKeyBytes,
 		},
 		networkUpdates:    make(chan *routingMsg),
-		topologyClients:   make(map[uint64]*topologyClient),
+		topologyClients:   &lnutils.SyncMap[uint64, *topologyClient]{},
 		ntfnClientUpdates: make(chan *topologyClientUpdate),
 		channelEdgeMtx:    multimutex.NewMutex(),
 		selfNode:          selfNode,
@@ -1203,14 +1202,10 @@ func (r *ChannelRouter) networkHandler() {
 			clientID := ntfnUpdate.clientID
 
 			if ntfnUpdate.cancel {
-				r.RLock()
-				client, ok := r.topologyClients[ntfnUpdate.clientID]
-				r.RUnlock()
+				client, ok := r.topologyClients.LoadAndDelete(
+					clientID,
+				)
 				if ok {
-					r.Lock()
-					delete(r.topologyClients, clientID)
-					r.Unlock()
-
 					close(client.exit)
 					client.wg.Wait()
 
@@ -1220,12 +1215,10 @@ func (r *ChannelRouter) networkHandler() {
 				continue
 			}
 
-			r.Lock()
-			r.topologyClients[ntfnUpdate.clientID] = &topologyClient{
+			r.topologyClients.Store(clientID, &topologyClient{
 				ntfnChan: ntfnUpdate.ntfnChan,
 				exit:     make(chan struct{}),
-			}
-			r.Unlock()
+			})
 
 		// The graph prune ticker has ticked, so we'll examine the
 		// state of the known graph to filter out any zombie channels