autopilot: for ConstrainedPrefAttachment.Select factor in skipNodes

This commit modifies the Select method for the ConstrainedPrefAttachment attachment heuristic slightly. Previously, it was possible for an autopilot.Agent to go over the allotted number of channels as it would unconditionally attempt to establish channel with all returned Attachment Directives. To remedy this, we now assume that we already have active, or pending channels to each of the nodes in the set of skipNodes. Therefore, we now use the size of the skipNodes map as an upper limit within the primary selection loop.
ProofOfKeags · Aug 22, 2017 · 77e3e74 · 77e3e74
1 parent a8576ea
commit 77e3e74
Show file tree

Hide file tree

Showing 2 changed files with 6 additions and 2 deletions.
diff --git a/autopilot/interface.go b/autopilot/interface.go
@@ -112,6 +112,8 @@ type AttachmentHeuristic interface {
 	// indeed need more channels, then the second argument returned will
 	// represent the amount of additional funds to be used towards creating
 	// channels.
+	//
+	// TODO(roasbeef): return number of chans? ensure doesn't go over
 	NeedMoreChans(chans []Channel, balance btcutil.Amount) (btcutil.Amount, bool)
 
 	// Select is a method that given the current state of the channel

diff --git a/autopilot/prefattach.go b/autopilot/prefattach.go
@@ -122,7 +122,8 @@ func NewNodeID(pub *btcec.PublicKey) NodeID {
 //
 // NOTE: This is a part of the AttachmentHeuristic interface.
 func (p *ConstrainedPrefAttachment) Select(self *btcec.PublicKey, g ChannelGraph,
-	fundsAvailable btcutil.Amount, skipNodes map[NodeID]struct{}) ([]AttachmentDirective, error) {
+	fundsAvailable btcutil.Amount,
+	skipNodes map[NodeID]struct{}) ([]AttachmentDirective, error) {
 
 	// TODO(roasbeef): rename?
 
@@ -135,7 +136,8 @@ func (p *ConstrainedPrefAttachment) Select(self *btcec.PublicKey, g ChannelGraph
 	// We'll continue our attachment loop until we've exhausted the current
 	// amount of available funds.
 	visited := make(map[NodeID]struct{})
-	for i := uint16(0); i < p.chanLimit; i++ {
+	chanLimit := p.chanLimit - uint16(len(skipNodes))
+	for i := uint16(0); i < chanLimit; i++ {
 		// selectionSlice will be used to randomly select a node
 		// according to a power law distribution. For each connected
 		// edge, we'll add an instance of the node to this slice. Thus,