op-node: Metrics in the channel bank

op-node/metrics/metrics.go

@@ -66,6 +66,9 @@ type Metricer interface {
 	RecordSequencerSealingTime(duration time.Duration)
 	Document() []metrics.DocumentedMetric
 	RecordChannelInputBytes(num int)
+	RecordHeadChannelOpened()
+	RecordChannelTimedOut()
+	RecordFrame()
 	// P2P Metrics
 	SetPeerScores(allScores []store.PeerScores)
 	ClientPayloadByNumberEvent(num uint64, resultCode byte, duration time.Duration)
@@ -132,6 +135,11 @@ type Metrics struct {
 
 	TransactionsSequencedTotal prometheus.Counter
 
+	// Channel Bank Metrics
+	headChannelOpenedEvent *EventMetrics
+	channelTimedOutEvent   *EventMetrics
+	frameAddedEvent        *EventMetrics
+
 	// P2P Metrics
 	PeerCount         prometheus.Gauge
 	StreamCount       prometheus.Gauge
@@ -363,6 +371,10 @@ func NewMetrics(procName string) *Metrics {
 			Help:      "Count of incoming dial attempts to accept, with label to filter to allowed attempts",
 		}, []string{"allow"}),
 
+		headChannelOpenedEvent: NewEventMetrics(factory, ns, "head_channel", "New channel at the front of the channel bank"),
+		channelTimedOutEvent:   NewEventMetrics(factory, ns, "channel_timeout", "Channel has timed out"),
+		frameAddedEvent:        NewEventMetrics(factory, ns, "frame_added", "New frame ingested in the channel bank"),
+
 		ChannelInputBytes: factory.NewCounter(prometheus.CounterOpts{
 			Namespace: ns,
 			Name:      "channel_input_bytes",
@@ -700,6 +712,18 @@ func (m *Metrics) RecordChannelInputBytes(inputCompressedBytes int) {
 	m.ChannelInputBytes.Add(float64(inputCompressedBytes))
 }
 
+func (m *Metrics) RecordHeadChannelOpened() {
+	m.headChannelOpenedEvent.RecordEvent()
+}
+
+func (m *Metrics) RecordChannelTimedOut() {
+	m.channelTimedOutEvent.RecordEvent()
+}
+
+func (m *Metrics) RecordFrame() {
+	m.frameAddedEvent.RecordEvent()
+}
+
 func (m *Metrics) RecordPeerUnban() {
 	m.PeerUnbans.Inc()
 }
@@ -830,6 +854,15 @@ func (n *noopMetricer) PayloadsQuarantineSize(int) {
 func (n *noopMetricer) RecordChannelInputBytes(int) {
 }
 
+func (n *noopMetricer) RecordHeadChannelOpened() {
+}
+
+func (n *noopMetricer) RecordChannelTimedOut() {
+}
+
+func (n *noopMetricer) RecordFrame() {
+}
+
 func (n *noopMetricer) RecordPeerUnban() {
 }
 

op-node/rollup/derive/channel_bank.go

@@ -29,8 +29,9 @@ type NextFrameProvider interface {
 
 // ChannelBank buffers channel frames, and emits full channel data
 type ChannelBank struct {
-	log log.Logger
-	cfg *rollup.Config
+	log     log.Logger
+	cfg     *rollup.Config
+	metrics Metrics
 
 	channels     map[ChannelID]*Channel // channels by ID
 	channelQueue []ChannelID            // channels in FIFO order
@@ -42,10 +43,11 @@ type ChannelBank struct {
 var _ ResettableStage = (*ChannelBank)(nil)
 
 // NewChannelBank creates a ChannelBank, which should be Reset(origin) before use.
-func NewChannelBank(log log.Logger, cfg *rollup.Config, prev NextFrameProvider, fetcher L1Fetcher) *ChannelBank {
+func NewChannelBank(log log.Logger, cfg *rollup.Config, prev NextFrameProvider, fetcher L1Fetcher, m Metrics) *ChannelBank {
 	return &ChannelBank{
 		log:          log,
 		cfg:          cfg,
+		metrics:      m,
 		channels:     make(map[ChannelID]*Channel),
 		channelQueue: make([]ChannelID, 0, 10),
 		prev:         prev,
@@ -83,6 +85,10 @@ func (cb *ChannelBank) IngestFrame(f Frame) {
 
 	currentCh, ok := cb.channels[f.ID]
 	if !ok {
+		// Only record a head channel if it can immediately be active.
+		if len(cb.channelQueue) == 0 {
+			cb.metrics.RecordHeadChannelOpened()
+		}
 		// create new channel if it doesn't exist yet
 		currentCh = NewChannel(f.ID, origin)
 		cb.channels[f.ID] = currentCh
@@ -101,6 +107,7 @@ func (cb *ChannelBank) IngestFrame(f Frame) {
 		log.Warn("failed to ingest frame into channel", "err", err)
 		return
 	}
+	cb.metrics.RecordFrame()
 
 	// Prune after the frame is loaded.
 	cb.prune()
@@ -117,8 +124,13 @@ func (cb *ChannelBank) Read() (data []byte, err error) {
 	timedOut := ch.OpenBlockNumber()+cb.cfg.ChannelTimeout < cb.Origin().Number
 	if timedOut {
 		cb.log.Info("channel timed out", "channel", first, "frames", len(ch.inputs))
+		cb.metrics.RecordChannelTimedOut()
 		delete(cb.channels, first)
 		cb.channelQueue = cb.channelQueue[1:]
+		// There is a new head channel if there is a channel after we have removed the first channel
+		if len(cb.channelQueue) > 0 {
+			cb.metrics.RecordHeadChannelOpened()
+		}
 		return nil, nil // multiple different channels may all be timed out
 	}
 	if !ch.IsReady() {
@@ -128,6 +140,10 @@ func (cb *ChannelBank) Read() (data []byte, err error) {
 
 	delete(cb.channels, first)
 	cb.channelQueue = cb.channelQueue[1:]
+	// There is a new head channel if there is a channel after we have removed the first channel
+	if len(cb.channelQueue) > 0 {
+		cb.metrics.RecordHeadChannelOpened()
+	}
 	r := ch.Reader()
 	// Suppress error here. io.ReadAll does return nil instead of io.EOF though.
 	data, _ = io.ReadAll(r)

op-node/rollup/derive/channel_bank_test.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/ethereum-optimism/optimism/op-node/metrics"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
 	"github.com/ethereum-optimism/optimism/op-node/testlog"
 	"github.com/ethereum-optimism/optimism/op-node/testutils"
@@ -101,7 +102,7 @@ func TestChannelBankSimple(t *testing.T) {
 
 	cfg := &rollup.Config{ChannelTimeout: 10}
 
-	cb := NewChannelBank(testlog.Logger(t, log.LvlCrit), cfg, input, nil)
+	cb := NewChannelBank(testlog.Logger(t, log.LvlCrit), cfg, input, nil, metrics.NoopMetrics)
 
 	// Load the first frame
 	out, err := cb.NextData(context.Background())
@@ -145,7 +146,7 @@ func TestChannelBankInterleaved(t *testing.T) {
 
 	cfg := &rollup.Config{ChannelTimeout: 10}
 
-	cb := NewChannelBank(testlog.Logger(t, log.LvlCrit), cfg, input, nil)
+	cb := NewChannelBank(testlog.Logger(t, log.LvlCrit), cfg, input, nil, metrics.NoopMetrics)
 
 	// Load a:0
 	out, err := cb.NextData(context.Background())
@@ -205,7 +206,7 @@ func TestChannelBankDuplicates(t *testing.T) {
 
 	cfg := &rollup.Config{ChannelTimeout: 10}
 
-	cb := NewChannelBank(testlog.Logger(t, log.LvlCrit), cfg, input, nil)
+	cb := NewChannelBank(testlog.Logger(t, log.LvlCrit), cfg, input, nil, metrics.NoopMetrics)
 
 	// Load the first frame
 	out, err := cb.NextData(context.Background())

op-node/rollup/derive/pipeline.go

@@ -18,6 +18,9 @@ type Metrics interface {
 	RecordL2Ref(name string, ref eth.L2BlockRef)
 	RecordUnsafePayloadsBuffer(length uint64, memSize uint64, next eth.BlockID)
 	RecordChannelInputBytes(inputCompressedBytes int)
+	RecordHeadChannelOpened()
+	RecordChannelTimedOut()
+	RecordFrame()
 }
 
 type L1Fetcher interface {
@@ -85,7 +88,7 @@ func NewDerivationPipeline(log log.Logger, cfg *rollup.Config, l1Fetcher L1Fetch
 	dataSrc := NewDataSourceFactory(log, cfg, l1Fetcher) // auxiliary stage for L1Retrieval
 	l1Src := NewL1Retrieval(log, dataSrc, l1Traversal)
 	frameQueue := NewFrameQueue(log, l1Src)
-	bank := NewChannelBank(log, cfg, frameQueue, l1Fetcher)
+	bank := NewChannelBank(log, cfg, frameQueue, l1Fetcher, metrics)
 	chInReader := NewChannelInReader(log, bank, metrics)
 	batchQueue := NewBatchQueue(log, cfg, chInReader)
 	attrBuilder := NewFetchingAttributesBuilder(cfg, l1Fetcher, engine)

op-node/rollup/driver/driver.go

@@ -23,6 +23,9 @@ type Metrics interface {
 	RecordL1Ref(name string, ref eth.L1BlockRef)
 	RecordL2Ref(name string, ref eth.L2BlockRef)
 	RecordChannelInputBytes(inputCompressedBytes int)
+	RecordHeadChannelOpened()
+	RecordChannelTimedOut()
+	RecordFrame()
 
 	RecordUnsafePayloadsBuffer(length uint64, memSize uint64, next eth.BlockID)
 

op-node/testutils/metrics.go

@@ -44,6 +44,15 @@ func (t *TestDerivationMetrics) RecordChannelInputBytes(inputCompressedBytes int
 	}
 }
 
+func (t *TestDerivationMetrics) RecordHeadChannelOpened() {
+}
+
+func (t *TestDerivationMetrics) RecordChannelTimedOut() {
+}
+
+func (t *TestDerivationMetrics) RecordFrame() {
+}
+
 type TestRPCMetrics struct{}
 
 func (n *TestRPCMetrics) RecordRPCServerRequest(method string) func() {