feat(indexer): Add metrics to indexer/api

indexer/api/api.go

@@ -8,6 +8,7 @@ import (
 	"github.com/ethereum-optimism/optimism/indexer/api/routes"
 	"github.com/ethereum-optimism/optimism/indexer/database"
 	"github.com/ethereum-optimism/optimism/op-service/httputil"
+	"github.com/ethereum-optimism/optimism/op-service/metrics"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
@@ -16,19 +17,34 @@ import (
 const ethereumAddressRegex = `^0x[a-fA-F0-9]{40}$`
 
 type Api struct {
-	log    log.Logger
-	Router *chi.Mux
+	log           log.Logger
+	Router        *chi.Mux
+	MetricsRouter *chi.Mux
 }
 
+const (
+	MetricsNamespace = "op_indexer"
+)
+
 func NewApi(logger log.Logger, bv database.BridgeTransfersView) *Api {
-	r := chi.NewRouter()
-	h := routes.NewRoutes(logger, bv, r)
+	apiRouter := chi.NewRouter()
+	h := routes.NewRoutes(logger, bv, apiRouter)
+
+	apiRouter.Use(middleware.Heartbeat("/healthz"))
+
+	apiRouter.Get(fmt.Sprintf("/api/v0/deposits/{address:%s}", ethereumAddressRegex), h.L1DepositsHandler)
+	apiRouter.Get(fmt.Sprintf("/api/v0/withdrawals/{address:%s}", ethereumAddressRegex), h.L2WithdrawalsHandler)
+
+	metricsRouter := chi.NewRouter()
+	registry := metrics.NewRegistry()
+	promRecorder := metrics.NewPromHTTPRecorder(registry, MetricsNamespace)
+	promHandler := metrics.NewHTTPRecordingMiddleware(promRecorder, apiRouter)
 
-	r.Use(middleware.Heartbeat("/healthz"))
+	metricsRouter.Use(middleware.Heartbeat("/healthz"))
 
-	r.Get(fmt.Sprintf("/api/v0/deposits/{address:%s}", ethereumAddressRegex), h.L1DepositsHandler)
-	r.Get(fmt.Sprintf("/api/v0/withdrawals/{address:%s}", ethereumAddressRegex), h.L2WithdrawalsHandler)
-	return &Api{log: logger, Router: r}
+	metricsRouter.Get("/metrics", promHandler.ServeHTTP)
+
+	return &Api{log: logger, Router: apiRouter, MetricsRouter: metricsRouter}
 }
 
 func (a *Api) Listen(ctx context.Context, port int) error {
@@ -43,3 +59,17 @@ func (a *Api) Listen(ctx context.Context, port int) error {
 
 	return err
 }
+
+func (a *Api) ListenMetrics(ctx context.Context, port int) error {
+	a.log.Info("metrics server listening...", "port", port)
+
+	server := http.Server{Addr: fmt.Sprintf(":%d", port), Handler: a.MetricsRouter}
+	err := httputil.ListenAndServeContext(ctx, &server)
+	if err != nil {
+		a.log.Error("api server stopped", "err", err)
+	} else {
+		a.log.Info("api server stopped")
+	}
+
+	return err
+}