Add isActiveSequencer to ExpressLaneTracker log messages

When running multiple sequencers in HA mode, all nodes run an
ExpressLaneTracker that polls for auction resolution events. This means
the "AuctionResolved" and "New express lane auction round" log messages
appear on every sequencer node, making it difficult for operators to
distinguish which node is active vs standby.

Add isActiveSequencer field to these log messages so operators can
identify whether the logging node is the active sequencer (sequencing
transactions) or an inactive one (validating and forwarding, ready for
failover).

The active status is determined by checking if the sequencer's forwarder
is nil - active sequencers don't have a forwarder, while inactive ones
forward to the active sequencer.

Author: Tristan-Wilson

cmd/el-proxy/main.go

@@ -130,6 +130,7 @@ func NewExpressLaneProxy(
 		&params.ChainConfig{ChainID: big.NewInt(config.ChainId)},
 		config.MaxTxDataSize,
 		0,
+		nil,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("error creating express lane tracker: %w", err)

execution/gethexec/express_lane_tracker.go

@@ -46,6 +46,7 @@ type ExpressLaneTracker struct {
 
 	roundControl containers.SyncMap[uint64, common.Address] // thread safe
 	useLogs      bool
+	isActiveFunc func() bool // nil means unknown/not applicable
 }
 
 func NewExpressLaneTracker(
@@ -56,7 +57,9 @@ func NewExpressLaneTracker(
 	auctionContractAddr common.Address,
 	chainConfig *params.ChainConfig,
 	maxTxSize uint64,
-	earlySubmissionGrace time.Duration) (*ExpressLaneTracker, error) {
+	earlySubmissionGrace time.Duration,
+	isActiveFunc func() bool,
+) (*ExpressLaneTracker, error) {
 	if err := ValidateMaxTxDataSize(maxTxSize); err != nil {
 		return nil, err
 	}
@@ -70,6 +73,7 @@ func NewExpressLaneTracker(
 		chainConfig:          chainConfig,
 		maxTxSize:            maxTxSize,
 		useLogs:              false, // default to use contract polling
+		isActiveFunc:         isActiveFunc,
 	}, nil
 }
 
@@ -146,6 +150,13 @@ func (t *ExpressLaneTracker) AuctionContractAddr() common.Address {
 	return t.auctionContractAddr
 }
 
+func (t *ExpressLaneTracker) isActiveSequencer() bool {
+	if t.isActiveFunc == nil {
+		return false
+	}
+	return t.isActiveFunc()
+}
+
 // --- internals ---
 
 func (t *ExpressLaneTracker) startViaLogIterator(ctxIn context.Context) {
@@ -207,6 +218,7 @@ func (t *ExpressLaneTracker) startViaLogIterator(ctxIn context.Context) {
 					"round", it.Event.Round,
 					"controller", it.Event.FirstPriceExpressLaneController,
 					"timeSinceAuctionClose", timeSinceAuctionClose,
+					"isActiveSequencer", t.isActiveSequencer(),
 				)
 
 				t.roundControl.Store(it.Event.Round, it.Event.FirstPriceExpressLaneController)
@@ -262,6 +274,7 @@ func (t *ExpressLaneTracker) startViaContractPolling(ctxIn context.Context) {
 						"round", record.round,
 						"controller", record.controller,
 						"timeSinceAuctionClose", timeSinceAuctionClose,
+						"isActiveSequencer", t.isActiveSequencer(),
 					)
 				}
 
@@ -304,6 +317,7 @@ func (t *ExpressLaneTracker) roundHeartbeatThread() {
 				"round", round,
 				"timestamp", ti,
 				"haveController", ok,
+				"isActiveSequencer", t.isActiveSequencer(),
 			)
 
 			// Cleanup previous round controller data

execution/gethexec/node.go

@@ -595,6 +595,14 @@ func (n *ExecutionNode) InitializeTimeboost(ctx context.Context, chainConfig *pa
 			return err
 		}
 
+		var isActiveFunc func() bool
+		if n.Sequencer != nil {
+			isActiveFunc = func() bool {
+				_, forwarder := n.Sequencer.GetPauseAndForwarder()
+				return forwarder == nil
+			}
+		}
+
 		expressLaneTracker, err := NewExpressLaneTracker(
 			*roundTimingInfo,
 			execNodeConfig.Sequencer.MaxBlockSpeed,
@@ -604,6 +612,7 @@ func (n *ExecutionNode) InitializeTimeboost(ctx context.Context, chainConfig *pa
 			chainConfig,
 			uint64(execNodeConfig.Sequencer.MaxTxDataSize), // #nosec G115
 			execNodeConfig.Sequencer.Timeboost.EarlySubmissionGrace,
+			isActiveFunc,
 		)
 		if err != nil {
 			return fmt.Errorf("error creating express lane tracker: %w", err)

system_tests/timeboost_test.go

@@ -1715,6 +1715,7 @@ func setupExpressLaneAuction(
 		builderSeq.chainConfig,
 		uint64(builderSeq.execConfig.Sequencer.MaxTxDataSize), // #nosec G115
 		builderSeq.execConfig.Sequencer.Timeboost.EarlySubmissionGrace,
+		nil,
 	)
 	Require(t, err)