From 9a75400295ac23d1e6ffb57bdbaf74db7725b6f4 Mon Sep 17 00:00:00 2001
From: ziggie <ziggie1984@protonmail.com>
Date: Sun, 6 Jul 2025 09:28:53 +0200
Subject: [PATCH] multi: add logs to debug potential payment sending issue

---
 htlcswitch/switch.go     |  3 +++
 routing/bandwidth.go     |  5 ++++-
 routing/pathfind.go      | 20 ++++++++++++++++++++
 routing/unified_edges.go |  3 ++-
 4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/htlcswitch/switch.go b/htlcswitch/switch.go
index 38b308b69..0d85805b9 100644
--- a/htlcswitch/switch.go
+++ b/htlcswitch/switch.go
@@ -2229,6 +2229,9 @@ func (s *Switch) GetLinkByShortID(chanID lnwire.ShortChannelID) (ChannelLink,
 func (s *Switch) getLinkByShortID(chanID lnwire.ShortChannelID) (ChannelLink, error) {
 	link, ok := s.forwardingIndex[chanID]
 	if !ok {
+		log.Debugf("Link not found in forwarding index using "+
+			"chanID=%v", chanID)
+
 		return nil, ErrChannelLinkNotFound
 	}
 
diff --git a/routing/bandwidth.go b/routing/bandwidth.go
index e9cfb5968..31466e78b 100644
--- a/routing/bandwidth.go
+++ b/routing/bandwidth.go
@@ -91,7 +91,10 @@ func (b *bandwidthManager) getBandwidth(cid lnwire.ShortChannelID,
 	if err != nil {
 		// If the link isn't online, then we'll report that it has
 		// zero bandwidth.
-		log.Warnf("ShortChannelID=%v: link not found: %v", cid, err)
+		log.Warnf("ShortChannelID=%v: link not found when "+
+			"determining bandwidth for local channel=%v, "+
+			"reporting 0 bandwidth", cid, err)
+
 		return 0
 	}
 
diff --git a/routing/pathfind.go b/routing/pathfind.go
index f489173f9..91bec3861 100644
--- a/routing/pathfind.go
+++ b/routing/pathfind.go
@@ -514,7 +514,18 @@ func getOutgoingBalance(node route.Vertex, outgoingChans map[uint64]struct{},
 
 	var max, total lnwire.MilliSatoshi
 	cb := func(channel *graphdb.DirectedChannel) error {
+		shortID := lnwire.NewShortChanIDFromInt(channel.ChannelID)
+
+		// This log line is needed to debug issues in case we do not
+		// have a channel in our graph for some reason when evaluating
+		// the local balance. Otherwise we could not tell whether all
+		// channels are being evaluated.
+		log.Tracef("Evaluating channel %v for local balance", shortID)
+
 		if !channel.OutPolicySet {
+			log.Debugf("ShortChannelID=%v: has no out policy set, "+
+				"skipping", shortID)
+
 			return nil
 		}
 
@@ -536,6 +547,12 @@ func getOutgoingBalance(node route.Vertex, outgoingChans map[uint64]struct{},
 		// we've already queried the bandwidth hints.
 		if !ok {
 			bandwidth = lnwire.NewMSatFromSatoshis(channel.Capacity)
+
+			log.Warnf("ShortChannelID=%v: not found in the local "+
+				"channels map of the bandwidth manager, "+
+				"using channel capacity=%v as bandwidth for "+
+				"this channel", shortID, bandwidth,
+			)
 		}
 
 		if bandwidth > max {
@@ -545,6 +562,9 @@ func getOutgoingBalance(node route.Vertex, outgoingChans map[uint64]struct{},
 		var overflow bool
 		total, overflow = overflowSafeAdd(total, bandwidth)
 		if overflow {
+			log.Warnf("ShortChannelID=%v: overflow detected, "+
+				"setting total to max value", shortID)
+
 			// If the current total and the bandwidth would
 			// overflow the maximum value, we set the total to the
 			// maximum value. Which is more milli-satoshis than are
diff --git a/routing/unified_edges.go b/routing/unified_edges.go
index 9e28a53c0..bf2f75dbf 100644
--- a/routing/unified_edges.go
+++ b/routing/unified_edges.go
@@ -280,8 +280,9 @@ func (u *edgeUnifier) getEdgeLocal(netAmtReceived lnwire.MilliSatoshi,
 			edge.policy.ChannelID, amt,
 		)
 		if !ok {
-			log.Debugf("Cannot get bandwidth for edge %v, use max "+
+			log.Warnf("Cannot get bandwidth for edge %v, use max "+
 				"instead", edge.policy.ChannelID)
+
 			bandwidth = lnwire.MaxMilliSatoshi
 		}