multi: add debug logs for edge policy flow

This commit adds more logs around the ChannelUpdate->edge policy process
flow.

graph/db/graph.go

@@ -2797,6 +2797,10 @@ func (c *ChannelGraph) UpdateEdgePolicy(edge *models.ChannelEdgePolicy,
 				tx, edge, c.graphCache,
 			)
 
+			if err != nil {
+				log.Errorf("UpdateEdgePolicy faild: %v", err)
+			}
+
 			// Silence ErrEdgeNotFound so that the batch can
 			// succeed, but propagate the error via local state.
 			if errors.Is(err, ErrEdgeNotFound) {

graph/db/graph_cache.go

@@ -228,6 +228,9 @@ func (c *GraphCache) UpdatePolicy(policy *models.ChannelEdgePolicy, fromNode,
 	var inboundFee lnwire.Fee
 	_, err := policy.ExtraOpaqueData.ExtractRecords(&inboundFee)
 	if err != nil {
+		log.Errorf("Failed to extract records from edge policy %v: %v",
+			policy.ChannelID, err)
+
 		return
 	}
 
@@ -236,11 +239,16 @@ func (c *GraphCache) UpdatePolicy(policy *models.ChannelEdgePolicy, fromNode,
 
 	updatePolicy := func(nodeKey route.Vertex) {
 		if len(c.nodeChannels[nodeKey]) == 0 {
+			log.Warnf("Node=%v not found in graph cache", nodeKey)
+
 			return
 		}
 
 		channel, ok := c.nodeChannels[nodeKey][policy.ChannelID]
 		if !ok {
+			log.Warnf("Channel=%v not found in graph cache",
+				policy.ChannelID)
+
 			return
 		}
 

graph/db/models/channel_edge_policy.go

@@ -1,6 +1,7 @@
 package models
 
 import (
+	"fmt"
 	"time"
 
 	"github.com/btcsuite/btcd/btcec/v2/ecdsa"
@@ -113,3 +114,10 @@ func (c *ChannelEdgePolicy) ComputeFee(
 
 	return c.FeeBaseMSat + (amt*c.FeeProportionalMillionths)/feeRateParts
 }
+
+// String returns a human-readable version of the channel edge policy.
+func (c *ChannelEdgePolicy) String() string {
+	return fmt.Sprintf("ChannelID=%v, MessageFlags=%v, ChannelFlags=%v, "+
+		"LastUpdate=%v", c.ChannelID, c.MessageFlags, c.ChannelFlags,
+		c.LastUpdate)
+}