graph+autopilot: let autopilot use new graph ForEachNode method

Which passes a NodeRTx to the call-back instead of a `kvdb.RTx`.

graph/db/graph.go

@@ -588,9 +588,9 @@ func (c *ChannelGraph) FetchNodeFeatures(
 	}
 }
 
-// ForEachNodeCached is similar to ForEachNode, but it utilizes the channel
+// ForEachNodeCached is similar to forEachNode, but it utilizes the channel
 // graph cache instead. Note that this doesn't return all the information the
-// regular ForEachNode method does.
+// regular forEachNode method does.
 //
 // NOTE: The callback contents MUST not be modified.
 func (c *ChannelGraph) ForEachNodeCached(cb func(node route.Vertex,
@@ -604,7 +604,7 @@ func (c *ChannelGraph) ForEachNodeCached(cb func(node route.Vertex,
 	// We'll iterate over each node, then the set of channels for each
 	// node, and construct a similar callback functiopn signature as the
 	// main funcotin expects.
-	return c.ForEachNode(func(tx kvdb.RTx,
+	return c.forEachNode(func(tx kvdb.RTx,
 		node *models.LightningNode) error {
 
 		channels := make(map[uint64]*DirectedChannel)
@@ -716,11 +716,25 @@ func (c *ChannelGraph) DisabledChannelIDs() ([]uint64, error) {
 // ForEachNode iterates through all the stored vertices/nodes in the graph,
 // executing the passed callback with each node encountered. If the callback
 // returns an error, then the transaction is aborted and the iteration stops
+// early. Any operations performed on the NodeTx passed to the call-back are
+// executed under the same read transaction and so, methods on the NodeTx object
+// _MUST_ only be called from within the call-back.
+func (c *ChannelGraph) ForEachNode(cb func(tx NodeRTx) error) error {
+	return c.forEachNode(func(tx kvdb.RTx,
+		node *models.LightningNode) error {
+
+		return cb(newChanGraphNodeTx(tx, c, node))
+	})
+}
+
+// forEachNode iterates through all the stored vertices/nodes in the graph,
+// executing the passed callback with each node encountered. If the callback
+// returns an error, then the transaction is aborted and the iteration stops
 // early.
 //
 // TODO(roasbeef): add iterator interface to allow for memory efficient graph
 // traversal when graph gets mega
-func (c *ChannelGraph) ForEachNode(
+func (c *ChannelGraph) forEachNode(
 	cb func(kvdb.RTx, *models.LightningNode) error) error {
 
 	traversal := func(tx kvdb.RTx) error {

graph/db/graph_cache_test.go

@@ -121,7 +121,7 @@ func TestGraphCacheAddNode(t *testing.T) {
 		assertCachedPolicyEqual(t, outPolicy1, toChannels[0].InPolicy)
 
 		// Now that we've inserted two nodes into the graph, check that
-		// we'll recover the same set of channels during ForEachNode.
+		// we'll recover the same set of channels during forEachNode.
 		nodes := make(map[route.Vertex]struct{})
 		chans := make(map[uint64]struct{})
 		_ = cache.ForEachNode(func(node route.Vertex,

graph/db/graph_test.go

@@ -1092,7 +1092,7 @@ func TestGraphTraversalCacheable(t *testing.T) {
 	// Create a map of all nodes with the iteration we know works (because
 	// it is tested in another test).
 	nodeMap := make(map[route.Vertex]struct{})
-	err = graph.ForEachNode(
+	err = graph.forEachNode(
 		func(tx kvdb.RTx, n *models.LightningNode) error {
 			nodeMap[n.PubKeyBytes] = struct{}{}
 
@@ -1217,7 +1217,7 @@ func fillTestGraph(t require.TestingT, graph *ChannelGraph, numNodes,
 
 	// Iterate over each node as returned by the graph, if all nodes are
 	// reached, then the map created above should be empty.
-	err := graph.ForEachNode(
+	err := graph.forEachNode(
 		func(_ kvdb.RTx, node *models.LightningNode) error {
 			delete(nodeIndex, node.Alias)
 			return nil
@@ -1329,7 +1329,7 @@ func assertNumChans(t *testing.T, graph *ChannelGraph, n int) {
 
 func assertNumNodes(t *testing.T, graph *ChannelGraph, n int) {
 	numNodes := 0
-	err := graph.ForEachNode(
+	err := graph.forEachNode(
 		func(_ kvdb.RTx, _ *models.LightningNode) error {
 			numNodes++
 			return nil