feat(da): add metrics handler

main.go

@@ -6,11 +6,13 @@ import (
 	"fmt"
 	"log"
 	"net"
+	"net/http"
 	"os"
 	"os/signal"
 	"syscall"
 	"time"
 
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/rollkit/centralized-sequencer/sequencing"
 	sequencingGRPC "github.com/rollkit/go-sequencing/proxy/grpc"
 )
@@ -24,13 +26,15 @@ const (
 
 func main() {
 	var (
-		host          string
-		port          string
-		listenAll     bool
-		batchTime     time.Duration
-		da_address    string
-		da_namespace  string
-		da_auth_token string
+		host           string
+		port           string
+		listenAll      bool
+		batchTime      time.Duration
+		da_address     string
+		da_namespace   string
+		da_auth_token  string
+		metricsEnabled bool
+		metricsAddress string
 	)
 	flag.StringVar(&host, "host", defaultHost, "centralized sequencer host")
 	flag.StringVar(&port, "port", defaultPort, "centralized sequencer port")
@@ -39,6 +43,8 @@ func main() {
 	flag.StringVar(&da_address, "da_address", defaultDA, "DA address")
 	flag.StringVar(&da_namespace, "da_namespace", "", "DA namespace where the sequencer submits transactions")
 	flag.StringVar(&da_auth_token, "da_auth_token", "", "auth token for the DA")
+	flag.BoolVar(&metricsEnabled, "metrics", false, "Enable Prometheus metrics")
+	flag.StringVar(&metricsAddress, "metrics-address", ":8080", "Address to expose Prometheus metrics")
 
 	flag.Parse()
 
@@ -58,7 +64,18 @@ func main() {
 		log.Fatalf("Error decoding namespace: %v", err)
 	}
 
-	centralizedSeq, err := sequencing.NewSequencer(da_address, da_auth_token, namespace, batchTime)
+	if metricsEnabled {
+		go func() {
+			err := http.ListenAndServe(metricsAddress, nil)
+			if err != nil {
+				log.Fatalf("Failed to serve metrics: %v", err)
+			}
+			http.Handle("/metrics", promhttp.Handler())
+		}()
+	}
+
+	metrics := sequencing.DefaultMetricsProvider(metricsEnabled, hex.EncodeToString([]byte(da_namespace)))
+	centralizedSeq, err := sequencing.NewSequencer(da_address, da_auth_token, namespace, batchTime, metrics)
 	if err != nil {
 		log.Fatalf("Failed to create centralized sequencer: %v", err)
 	}

sequencing/metrics.go

@@ -13,6 +13,20 @@ const (
 	MetricsSubsystem = "sequencer"
 )
 
+// MetricsProvider returns sequencing Metrics.
+type MetricsProvider func(chainID string) *Metrics
+
+// DefaultMetricsProvider returns Metrics build using Prometheus client library
+// if Prometheus is enabled. Otherwise, it returns no-op Metrics.
+func DefaultMetricsProvider(enabled bool, namespace string) MetricsProvider {
+	return func(chainID string) *Metrics {
+		if enabled {
+			return PrometheusMetrics(namespace, "chain_id", chainID)
+		}
+		return NopMetrics()
+	}
+}
+
 // Metrics contains metrics exposed by this package.
 type Metrics struct {
 	// GasPrice

sequencing/sequencer.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"crypto/sha256"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"sync"
@@ -124,11 +125,12 @@ type Sequencer struct {
 	seenBatches map[string]struct{}
 	bq          *BatchQueue
 
+	metricsProvider MetricsProvider
 	metrics *Metrics
 }
 
 // NewSequencer ...
-func NewSequencer(daAddress, daAuthToken string, daNamespace []byte, batchTime time.Duration) (*Sequencer, error) {
+func NewSequencer(daAddress, daAuthToken string, daNamespace []byte, batchTime time.Duration, metricsProvider MetricsProvider) (*Sequencer, error) {
 	ctx := context.Background()
 	dac, err := proxyda.NewClient(daAddress, daAuthToken)
 	if err != nil {
@@ -147,6 +149,8 @@ func NewSequencer(daAddress, daAuthToken string, daNamespace []byte, batchTime t
 		tq:            NewTransactionQueue(),
 		bq:            NewBatchQueue(),
 		seenBatches:   make(map[string]struct{}),
+		metricsProvider: metricsProvider,
+		metrics: NopMetrics(), // Initialized from metricsProvider in SubmitRollupTransaction
 	}
 	go s.batchSubmissionLoop(s.ctx)
 	return s, nil
@@ -297,6 +301,7 @@ func hashSHA256(data []byte) []byte {
 func (c *Sequencer) SubmitRollupTransaction(ctx context.Context, rollupId []byte, tx []byte) error {
 	if c.rollupId == nil {
 		c.rollupId = rollupId
+		c.metrics = c.metricsProvider(hex.EncodeToString(rollupId))
 	} else {
 		if !bytes.Equal(c.rollupId, rollupId) {
 			return ErrorRollupIdMismatch