New metrics for tracking request and response size

pkg/rpcgateway/rpcgateway.go

@@ -25,6 +25,8 @@ type RPCGateway struct {
 
 	server                  *http.Server
 	metricRequestsProcessed *prometheus.CounterVec
+	metricRequestSize       *prometheus.HistogramVec
+	metricResponseSize      *prometheus.HistogramVec
 }
 
 func (r *RPCGateway) ServeHTTP(w http.ResponseWriter, req *http.Request) {
@@ -103,9 +105,45 @@ func NewRPCGateway(config RPCGatewayConfig) *RPCGateway {
 				"code",
 				"method",
 			}),
+		metricRequestSize: promauto.NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name: "zeroex_rpc_gateway_request_size_bytes",
+				Help: "Histogram of HTTP request sizes",
+				Buckets: []float64{
+					100,
+					250,
+					500,
+					1000,
+					1500,
+					2000,
+				},
+			}, []string{
+				"code",
+				"method",
+			},
+		),
+		metricResponseSize: promauto.NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name: "zeroex_rpc_gateway_response_size_bytes",
+				Help: "Histogram of HTTP responses sizes",
+				Buckets: []float64{
+					100,
+					250,
+					500,
+					1000,
+					1500,
+					2000,
+				},
+			}, []string{
+				"code",
+				"method",
+			},
+		),
 	}
 
-	handler := promhttp.InstrumentHandlerCounter(gateway.metricRequestsProcessed, httpFailoverProxy)
+	handler := promhttp.InstrumentHandlerCounter(gateway.metricRequestsProcessed,
+		promhttp.InstrumentHandlerRequestSize(gateway.metricRequestSize,
+			promhttp.InstrumentHandlerResponseSize(gateway.metricResponseSize, httpFailoverProxy)))
 
 	r.PathPrefix("/").Handler(handler)
 	r.PathPrefix("").Handler(handler)