eth: add per-peer metrics

Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>

eth/fetcher/tx_fetcher.go

@@ -310,6 +310,7 @@ func (f *TxFetcher) isKnownUnderpriced(hash common.Hash) bool {
 // direct request replies. The differentiation is important so the fetcher can
 // re-schedule missing transactions as soon as possible.
 func (f *TxFetcher) Enqueue(peer string, txs []*types.Transaction, direct bool) error {
+	// TODO: add peer metrics here
 	var (
 		inMeter          = txReplyInMeter
 		knownMeter       = txReplyKnownMeter

eth/protocols/eth/handlers.go

@@ -501,6 +501,7 @@ func handleTransactions(backend Backend, msg Decoder, peer *Peer) error {
 		}
 		peer.markTransaction(tx.Hash())
 	}
+	peer.meters.txReceived.Mark(int64(len(txs)))
 	return backend.Handle(peer, &txs)
 }
 

eth/protocols/eth/peer.go

@@ -59,6 +59,8 @@ type Peer struct {
 	reqCancel   chan *cancel   // Dispatch channel to cancel pending requests and untrack them
 	resDispatch chan *response // Dispatch channel to fulfil pending requests and untrack them
 
+	meters *peerMeters // Peer-specific metrics for diagnositics and to use in decision logic
+
 	term chan struct{} // Termination channel to stop the broadcasters
 }
 
@@ -77,6 +79,7 @@ func NewPeer(version uint, p *p2p.Peer, rw p2p.MsgReadWriter, txpool TxPool) *Pe
 		reqCancel:   make(chan *cancel),
 		resDispatch: make(chan *response),
 		txpool:      txpool,
+		meters:      newPeerMeters("peers/"+p.ID().String(), nil),
 		term:        make(chan struct{}),
 	}
 	// Start up all the broadcasters

eth/protocols/eth/peer_metrics.go

@@ -0,0 +1,42 @@
+// Copyright 2025 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package eth
+
+import "github.com/ethereum/go-ethereum/metrics"
+
+type peerMeters struct {
+	txReceived *metrics.Meter
+	txSent     *metrics.Meter
+
+	txReplyInMeter          *metrics.Meter
+	txReplyKnownMeter       *metrics.Meter
+	txReplyUnderpricedMeter *metrics.Meter
+	txReplyOtherRejectMeter *metrics.Meter
+}
+
+// newPeerMeters registers and returns peer-level meters.
+func newPeerMeters(base string, r metrics.Registry) *peerMeters {
+	return &peerMeters{
+		txReceived: metrics.NewRegisteredMeter(base+"/txReceived", r),
+		txSent:     metrics.NewRegisteredMeter(base+"/txSent", r),
+
+		txReplyInMeter:          metrics.NewRegisteredMeter(base+"/eth/fetcher/transaction/replies/in", nil),
+		txReplyKnownMeter:       metrics.NewRegisteredMeter(base+"/eth/fetcher/transaction/replies/known", nil),
+		txReplyUnderpricedMeter: metrics.NewRegisteredMeter(base+"/eth/fetcher/transaction/replies/underpriced", nil),
+		txReplyOtherRejectMeter: metrics.NewRegisteredMeter(base+"/eth/fetcher/transaction/replies/otherreject", nil),
+	}
+}