routing: disable FilteredChainView when AssumeChannelValid is active

In this commit, we disable attempting to determine when a channel has
been closed out on-chain whenever AssumeChannelValid is active. Since
the flag indicates that performing this operation is expensive, we do
this as a temporary optimization until we can include proofs of channels
being closed in the gossip protocol.

With this change, the only way for channels being removed from the graph
will be once they're considered zombies: which can happen when both
edges of a channel have their disabled bits set or when both edges
haven't had an update within the past two weeks.

routing/router.go

@@ -200,8 +200,7 @@ type Config struct {
 
 	// AssumeChannelValid toggles whether or not the router will check for
 	// spentness of channel outpoints. For neutrino, this saves long rescans
-	// from blocking initial usage of the wallet. This should only be
+	// from blocking initial usage of the daemon.
-	// enabled on testnet.
 	AssumeChannelValid bool
 }
 
@@ -381,26 +380,15 @@ func (r *ChannelRouter) Start() error {
 
 	log.Tracef("Channel Router starting")
 
-	// First, we'll start the chain view instance (if it isn't already
-	// started).
-	if err := r.cfg.ChainView.Start(); err != nil {
-		return err
-	}
-
-	// Once the instance is active, we'll fetch the channel we'll receive
-	// notifications over.
-	r.newBlocks = r.cfg.ChainView.FilteredBlocks()
-	r.staleBlocks = r.cfg.ChainView.DisconnectedBlocks()
-
 	bestHash, bestHeight, err := r.cfg.Chain.GetBestBlock()
 	if err != nil {
 		return err
 	}
 
+	// If the graph has never been pruned, or hasn't fully been created yet,
+	// then we don't treat this as an explicit error.
 	if _, _, err := r.cfg.Graph.PruneTip(); err != nil {
 		switch {
-		// If the graph has never been pruned, or hasn't fully been
-		// created yet, then we don't treat this as an explicit error.
 		case err == channeldb.ErrGraphNeverPruned:
 			fallthrough
 		case err == channeldb.ErrGraphNotFound:
@@ -418,16 +406,38 @@ func (r *ChannelRouter) Start() error {
 		}
 	}
 
-	// Before we perform our manual block pruning, we'll construct and
+	// If AssumeChannelValid is present, then we won't rely on pruning
-	// apply a fresh chain filter to the active FilteredChainView instance.
+	// channels from the graph based on their spentness, but whether they
-	// We do this before, as otherwise we may miss on-chain events as the
+	// are considered zombies or not.
-	// filter hasn't properly been applied.
+	if r.cfg.AssumeChannelValid {
+		if err := r.pruneZombieChans(); err != nil {
+			return err
+		}
+	} else {
+		// Otherwise, we'll use our filtered chain view to prune
+		// channels as soon as they are detected as spent on-chain.
+		if err := r.cfg.ChainView.Start(); err != nil {
+			return err
+		}
+
+		// Once the instance is active, we'll fetch the channel we'll
+		// receive notifications over.
+		r.newBlocks = r.cfg.ChainView.FilteredBlocks()
+		r.staleBlocks = r.cfg.ChainView.DisconnectedBlocks()
+
+		// Before we perform our manual block pruning, we'll construct
+		// and apply a fresh chain filter to the active
+		// FilteredChainView instance.  We do this before, as otherwise
+		// we may miss on-chain events as the filter hasn't properly
+		// been applied.
 		channelView, err := r.cfg.Graph.ChannelView()
 		if err != nil && err != channeldb.ErrGraphNoEdgesFound {
 			return err
 		}
 
-	log.Infof("Filtering chain using %v channels active", len(channelView))
+		log.Infof("Filtering chain using %v channels active",
+			len(channelView))
+
 		if len(channelView) != 0 {
 			err = r.cfg.ChainView.UpdateFilter(
 				channelView, uint32(bestHeight),
@@ -437,19 +447,21 @@ func (r *ChannelRouter) Start() error {
 			}
 		}
 
-	// Before we begin normal operation of the router, we first need to
+		// Before we begin normal operation of the router, we first need
-	// synchronize the channel graph to the latest state of the UTXO set.
+		// to synchronize the channel graph to the latest state of the
+		// UTXO set.
 		if err := r.syncGraphWithChain(); err != nil {
 			return err
 		}
 
-	// Finally, before we proceed, we'll prune any unconnected nodes from
+		// Finally, before we proceed, we'll prune any unconnected nodes
-	// the graph in order to ensure we maintain a tight graph of "useful"
+		// from the graph in order to ensure we maintain a tight graph
-	// nodes.
+		// of "useful" nodes.
 		err = r.cfg.Graph.PruneGraphNodes()
 		if err != nil && err != channeldb.ErrGraphNodesNotFound {
 			return err
 		}
+	}
 
 	r.wg.Add(1)
 	go r.networkHandler()
@@ -465,11 +477,15 @@ func (r *ChannelRouter) Stop() error {
 		return nil
 	}
 
-	log.Infof("Channel Router shutting down")
+	log.Tracef("Channel Router shutting down")
 
+	// Our filtered chain view could've only been started if
+	// AssumeChannelValid isn't present.
+	if !r.cfg.AssumeChannelValid {
 		if err := r.cfg.ChainView.Stop(); err != nil {
 			return err
 		}
+	}
 
 	close(r.quit)
 	r.wg.Wait()
@@ -562,9 +578,9 @@ func (r *ChannelRouter) syncGraphWithChain() error {
 	log.Infof("Syncing channel graph from height=%v (hash=%v) to height=%v "+
 		"(hash=%v)", pruneHeight, pruneHash, bestHeight, bestHash)
 
-	// If we're not yet caught up, then we'll walk forward in the chain in
+	// If we're not yet caught up, then we'll walk forward in the chain
-	// the chain pruning the channel graph with each new block in the chain
+	// pruning the channel graph with each new block that hasn't yet been
-	// that hasn't yet been consumed by the channel graph.
+	// consumed by the channel graph.
 	var numChansClosed uint32
 	for nextHeight := pruneHeight + 1; nextHeight <= uint32(bestHeight); nextHeight++ {
 		// Using the next height, request a manual block pruning from
@@ -1121,9 +1137,10 @@ func (r *ChannelRouter) processUpdate(msg interface{}) error {
 			fundingPoint, msg.ChannelID, msg.Capacity)
 
 		// As a new edge has been added to the channel graph, we'll
-		// update the current UTXO filter within our active
+		// update the current UTXO filter, if AssumeChannelValid is not
-		// FilteredChainView so we are notified if/when this channel is
+		// present, within our active FilteredChainView so we are
-		// closed.
+		// notified if/when this channel is closed.
+		if !r.cfg.AssumeChannelValid {
 			filterUpdate := []channeldb.EdgePoint{
 				{
 					FundingPkScript: fundingPkScript,
@@ -1137,6 +1154,7 @@ func (r *ChannelRouter) processUpdate(msg interface{}) error {
 				return errors.Errorf("unable to update chain "+
 					"view: %v", err)
 			}
+		}
 
 	case *channeldb.ChannelEdgePolicy:
 		// If we recently rejected this channel edge, then we won't