graph+routing: let FetchNodeFeatures take a RTx

Most call-sites of this method have a read transaction available to pass
in. Note that this also means that calls to FetchNodeFeatures made from
the router are made under the same read transaction as calls to
ForEachNodeDirectedChannel which makes things cleaner.

graph/db/graph.go

@@ -524,7 +524,7 @@ func (c *ChannelGraph) ForEachNodeDirectedChannel(tx RTx,
 	toNodeCallback := func() route.Vertex {
 		return node
 	}
-	toNodeFeatures, err := c.FetchNodeFeatures(node)
+	toNodeFeatures, err := c.FetchNodeFeatures(tx, node)
 	if err != nil {
 		return err
 	}
@@ -570,15 +570,15 @@ func (c *ChannelGraph) ForEachNodeDirectedChannel(tx RTx,
 
 // FetchNodeFeatures returns the features of a given node. If no features are
 // known for the node, an empty feature vector is returned.
-func (c *ChannelGraph) FetchNodeFeatures(
+func (c *ChannelGraph) FetchNodeFeatures(tx RTx,
 	node route.Vertex) (*lnwire.FeatureVector, error) {
 
 	if c.graphCache != nil {
 		return c.graphCache.GetFeatures(node), nil
 	}
 
 	// Fallback that uses the database.
-	targetNode, err := c.FetchLightningNode(nil, node)
+	targetNode, err := c.FetchLightningNode(tx, node)
 	switch err {
 	// If the node exists and has features, return them directly.
 	case nil:
@@ -625,7 +625,7 @@ func (c *ChannelGraph) ForEachNodeCached(cb func(node route.Vertex,
 					return node.PubKeyBytes
 				}
 				toNodeFeatures, err := c.FetchNodeFeatures(
-					node.PubKeyBytes,
+					tx, node.PubKeyBytes,
 				)
 				if err != nil {
 					return err

graph/graphsession/graph_session.go

@@ -95,7 +95,7 @@ func (g *session) ForEachNodeChannel(nodePub route.Vertex,
 func (g *session) FetchNodeFeatures(nodePub route.Vertex) (
 	*lnwire.FeatureVector, error) {
 
-	return g.graph.FetchNodeFeatures(nodePub)
+	return g.graph.FetchNodeFeatures(g.tx, nodePub)
 }
 
 // A compile-time check to ensure that *session implements the
@@ -132,7 +132,8 @@ type graph interface {
 
 	// FetchNodeFeatures returns the features of a given node. If no
 	// features are known for the node, an empty feature vector is returned.
-	FetchNodeFeatures(node route.Vertex) (*lnwire.FeatureVector, error)
+	FetchNodeFeatures(tx graphdb.RTx, node route.Vertex) (
+		*lnwire.FeatureVector, error)
 }
 
 // A compile-time check to ensure that *channeldb.ChannelGraph implements the

routing/integrated_routing_context_test.go

@@ -400,5 +400,5 @@ func (g *mockGraphSessionChanDB) ForEachNodeChannel(nodePub route.Vertex,
 func (g *mockGraphSessionChanDB) FetchNodeFeatures(nodePub route.Vertex) (
 	*lnwire.FeatureVector, error) {
 
-	return g.graph.FetchNodeFeatures(nodePub)
+	return g.graph.FetchNodeFeatures(g.tx, nodePub)
 }