feat(go): expose gateway async sink metrics

go/vehicle-gateway/cmd/gateway/main.go

@@ -30,7 +30,8 @@ func main() {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
 
-	sink, err := buildSink(ctx, logger)
+	registry := metrics.NewRegistry()
+	sink, err := buildSink(ctx, logger, registry)
 	if err != nil {
 		logger.Error("build sink failed", "error", err)
 		os.Exit(1)
@@ -42,7 +43,6 @@ func main() {
 		os.Exit(1)
 	}
 	defer closeResolver()
-	registry := metrics.NewRegistry()
 	health.Start(ctx, logger, health.NewServer(env("HEALTH_ADDR", ""), "vehicle-gateway", nil, registry))
 	publishUnified := envBool("PUBLISH_UNIFIED_ENABLED", false)
 
@@ -161,7 +161,7 @@ func buildIdentityResolver(ctx context.Context, logger *slog.Logger) (identity.R
 	return resolver, func() { _ = db.Close() }, nil
 }
 
-func buildSink(ctx context.Context, logger *slog.Logger) (eventbus.Sink, error) {
+func buildSink(ctx context.Context, logger *slog.Logger, registry *metrics.Registry) (eventbus.Sink, error) {
 	if strings.TrimSpace(os.Getenv("NATS_URL")) != "" {
 		sink, err := eventbus.NewNATSSink(natsSinkConfigFromEnv())
 		if err != nil {
@@ -180,6 +180,8 @@ func buildSink(ctx context.Context, logger *slog.Logger) (eventbus.Sink, error)
 				QueueSize:        queueSize,
 				Workers:          workers,
 				OperationTimeout: timeout,
+				Metrics:          registry,
+				Name:             "nats",
 				OnError: func(err error) {
 					logger.Warn("nats async publish failed", "error", err)
 				},
@@ -235,6 +237,8 @@ func buildSink(ctx context.Context, logger *slog.Logger) (eventbus.Sink, error)
 			QueueSize:        queueSize,
 			Workers:          workers,
 			OperationTimeout: timeout,
+			Metrics:          registry,
+			Name:             "kafka",
 			OnError: func(err error) {
 				logger.Warn("kafka async publish failed", "error", err)
 			},

go/vehicle-gateway/cmd/gateway/main_test.go

@@ -56,6 +56,23 @@ func TestGatewayDefaultsTo100KConnectionCeiling(t *testing.T) {
 	}
 }
 
+func TestGatewayPassesMetricsRegistryToAsyncSink(t *testing.T) {
+	source, err := os.ReadFile("main.go")
+	if err != nil {
+		t.Fatalf("read main.go: %v", err)
+	}
+	for _, want := range []string{
+		"buildSink(ctx, logger, registry)",
+		"Metrics:          registry",
+		`Name:             "nats"`,
+		`Name:             "kafka"`,
+	} {
+		if !strings.Contains(string(source), want) {
+			t.Fatalf("gateway async sink metrics wiring missing %s", want)
+		}
+	}
+}
+
 func TestNATSSinkConfigFromEnvDefaultsToGoSubjects(t *testing.T) {
 	t.Setenv("NATS_URL", "nats://172.17.111.56:4222")