p2p, p2p/discover: add dial metrics (#27621)

This PR adds metrics for p2p dialing, which gives us visibility into the quality of the dial 
candidates  returned by our discovery methods.

p2p/discover/metrics.go

@@ -17,6 +17,7 @@
 package discover
 
 import (
+	"fmt"
 	"net"
 
 	"github.com/ethereum/go-ethereum/metrics"
@@ -32,10 +33,17 @@ const (
 )
 
 var (
+	bucketsCounter      []metrics.Counter
 	ingressTrafficMeter = metrics.NewRegisteredMeter(ingressMeterName, nil)
 	egressTrafficMeter  = metrics.NewRegisteredMeter(egressMeterName, nil)
 )
 
+func init() {
+	for i := 0; i < nBuckets; i++ {
+		bucketsCounter = append(bucketsCounter, metrics.NewRegisteredCounter(fmt.Sprintf("%s/bucket/%d/count", moduleName, i), nil))
+	}
+}
+
 // meteredConn is a wrapper around a net.UDPConn that meters both the
 // inbound and outbound network traffic.
 type meteredUdpConn struct {

p2p/discover/table.go

@@ -34,6 +34,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
 )
@@ -80,7 +81,8 @@ type Table struct {
 	closeReq   chan struct{}
 	closed     chan struct{}
 
-	nodeAddedHook func(*node) // for testing
+	nodeAddedHook   func(*bucket, *node)
+	nodeRemovedHook func(*bucket, *node)
 }
 
 // transport is implemented by the UDP transports.
@@ -98,6 +100,7 @@ type bucket struct {
 	entries      []*node // live entries, sorted by time of last contact
 	replacements []*node // recently seen nodes to be used if revalidation fails
 	ips          netutil.DistinctNetSet
+	index        int
 }
 
 func newTable(t transport, db *enode.DB, cfg Config) (*Table, error) {
@@ -119,7 +122,8 @@ func newTable(t transport, db *enode.DB, cfg Config) (*Table, error) {
 	}
 	for i := range tab.buckets {
 		tab.buckets[i] = &bucket{
-			ips: netutil.DistinctNetSet{Subnet: bucketSubnet, Limit: bucketIPLimit},
+			index: i,
+			ips:   netutil.DistinctNetSet{Subnet: bucketSubnet, Limit: bucketIPLimit},
 		}
 	}
 	tab.seedRand()
@@ -128,6 +132,22 @@ func newTable(t transport, db *enode.DB, cfg Config) (*Table, error) {
 	return tab, nil
 }
 
+func newMeteredTable(t transport, db *enode.DB, cfg Config) (*Table, error) {
+	tab, err := newTable(t, db, cfg)
+	if err != nil {
+		return nil, err
+	}
+	if metrics.Enabled {
+		tab.nodeAddedHook = func(b *bucket, n *node) {
+			bucketsCounter[b.index].Inc(1)
+		}
+		tab.nodeRemovedHook = func(b *bucket, n *node) {
+			bucketsCounter[b.index].Dec(1)
+		}
+	}
+	return tab, nil
+}
+
 // Nodes returns all nodes contained in the table.
 func (tab *Table) Nodes() []*enode.Node {
 	if !tab.isInitDone() {
@@ -495,7 +515,7 @@ func (tab *Table) addSeenNode(n *node) {
 	n.addedAt = time.Now()
 
 	if tab.nodeAddedHook != nil {
-		tab.nodeAddedHook(n)
+		tab.nodeAddedHook(b, n)
 	}
 }
 
@@ -539,7 +559,7 @@ func (tab *Table) addVerifiedNode(n *node) {
 	n.addedAt = time.Now()
 
 	if tab.nodeAddedHook != nil {
-		tab.nodeAddedHook(n)
+		tab.nodeAddedHook(b, n)
 	}
 }
 
@@ -638,8 +658,16 @@ func (tab *Table) bumpInBucket(b *bucket, n *node) bool {
 }
 
 func (tab *Table) deleteInBucket(b *bucket, n *node) {
+	// Check if the node is actually in the bucket so the removed hook
+	// isn't called multiple times for the same node.
+	if !contains(b.entries, n.ID()) {
+		return
+	}
 	b.entries = deleteNode(b.entries, n)
 	tab.removeIP(b, n.IP())
+	if tab.nodeRemovedHook != nil {
+		tab.nodeRemovedHook(b, n)
+	}
 }
 
 func contains(ns []*node, id enode.ID) bool {

p2p/discover/v4_udp.go

@@ -142,7 +142,7 @@ func ListenV4(c UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv4, error) {
 		log:             cfg.Log,
 	}
 
-	tab, err := newTable(t, ln.Database(), cfg)
+	tab, err := newMeteredTable(t, ln.Database(), cfg)
 	if err != nil {
 		return nil, err
 	}

p2p/discover/v4_udp_test.go

@@ -394,7 +394,7 @@ func TestUDPv4_pingMatchIP(t *testing.T) {
 func TestUDPv4_successfulPing(t *testing.T) {
 	test := newUDPTest(t)
 	added := make(chan *node, 1)
-	test.table.nodeAddedHook = func(n *node) { added <- n }
+	test.table.nodeAddedHook = func(b *bucket, n *node) { added <- n }
 	defer test.close()
 
 	// The remote side sends a ping packet to initiate the exchange.

p2p/discover/v5_udp.go

@@ -174,7 +174,7 @@ func newUDPv5(conn UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv5, error) {
 		cancelCloseCtx: cancelCloseCtx,
 	}
 	t.talk = newTalkSystem(t)
-	tab, err := newTable(t, t.db, cfg)
+	tab, err := newMeteredTable(t, t.db, cfg)
 	if err != nil {
 		return nil, err
 	}