Extract separate files/packages for better visibility.

gateway/metrics/metrics.go

@@ -18,3 +18,41 @@ type MetricOptions struct {
 func PrometheusHandler() http.Handler {
 	return prometheus.Handler()
 }
+
+func BuildMetricsOptions() MetricOptions {
+	GatewayRequestsTotal := prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "gateway_requests_total",
+		Help: "Total amount of HTTP requests to the gateway",
+	})
+	GatewayServerlessServedTotal := prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "gateway_serverless_invocation_total",
+		Help: "Total amount of serverless function invocations",
+	})
+	GatewayFunctions := prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name: "gateway_functions",
+		Help: "Gateway functions",
+	})
+	GatewayFunctionInvocation := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "gateway_function_invocation_total",
+			Help: "Individual function metrics",
+		},
+		[]string{"function_name"},
+	)
+
+	metricsOptions := MetricOptions{
+		GatewayRequestsTotal:         GatewayRequestsTotal,
+		GatewayServerlessServedTotal: GatewayServerlessServedTotal,
+		GatewayFunctions:             GatewayFunctions,
+		GatewayFunctionInvocation:    GatewayFunctionInvocation,
+	}
+
+	return metricsOptions
+}
+
+func RegisterMetrics(metricsOptions MetricOptions) {
+	prometheus.Register(metricsOptions.GatewayRequestsTotal)
+	prometheus.Register(metricsOptions.GatewayServerlessServedTotal)
+	prometheus.Register(metricsOptions.GatewayFunctions)
+	prometheus.Register(metricsOptions.GatewayFunctionInvocation)
+}