Add gateway client metrics

clients/gateway/event_listener.go

@@ -0,0 +1,17 @@
+package gateway
+
+import "time"
+
+type EventListener interface {
+	OnResponse(urlPath string, status int, took time.Duration)
+}
+
+type SelectiveListener struct {
+	OnResponseCb func(urlPath string, status int, took time.Duration)
+}
+
+func (l *SelectiveListener) OnResponse(urlPath string, status int, took time.Duration) {
+	if l.OnResponseCb != nil {
+		l.OnResponseCb(urlPath, status, took)
+	}
+}

clients/gateway/gateway.go

@@ -38,6 +38,7 @@ var (
 type Client struct {
 	url       string
 	client    *http.Client
+	listener  EventListener
 	log       utils.SimpleLogger
 	userAgent string
 	apiKey    string
@@ -53,6 +54,11 @@ func (c *Client) WithAPIKey(key string) *Client {
 	return c
 }
 
+func (c *Client) WithListener(l EventListener) *Client {
+	c.listener = l
+	return c
+}
+
 // NewTestClient returns a client and a function to close a test server.
 func NewTestClient(t *testing.T) *Client {
 	srv := newTestServer(t)
@@ -100,7 +106,8 @@ func NewClient(gatewayURL string, log utils.SimpleLogger) *Client {
 		client: &http.Client{
 			Timeout: time.Minute,
 		},
-		log: log,
+		listener: &SelectiveListener{},
+		log:      log,
 	}
 }
 
@@ -153,7 +160,13 @@ func (c *Client) doPost(ctx context.Context, url string, data any) (*http.Respon
 	if c.apiKey != "" {
 		req.Header.Set("X-Throttling-Bypass", c.apiKey)
 	}
-	return c.client.Do(req)
+	reqTimer := time.Now()
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	c.listener.OnResponse(req.URL.Path, resp.StatusCode, time.Since(reqTimer))
+	return resp, nil
 }
 
 type ErrorCode string

node/metrics.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/NethermindEth/juno/blockchain"
 	"github.com/NethermindEth/juno/clients/feeder"
+	"github.com/NethermindEth/juno/clients/gateway"
 	"github.com/NethermindEth/juno/core"
 	"github.com/NethermindEth/juno/db"
 	"github.com/NethermindEth/juno/jsonrpc"
@@ -245,3 +246,18 @@ func makeFeederMetrics() feeder.EventListener {
 		},
 	}
 }
+
+func makeGatewayMetrics() gateway.EventListener {
+	requestLatencies := prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "gateway",
+		Subsystem: "client",
+		Name:      "request_latency",
+	}, []string{"method", "status"})
+	prometheus.MustRegister(requestLatencies)
+	return &gateway.SelectiveListener{
+		OnResponseCb: func(urlPath string, status int, took time.Duration) {
+			statusString := strconv.FormatInt(int64(status), 10)
+			requestLatencies.WithLabelValues(urlPath, statusString).Observe(took.Seconds())
+		},
+	}
+}

node/node.go

@@ -181,6 +181,7 @@ func New(cfg *Config, version string) (*Node, error) { //nolint:gocyclo,funlen
 		jsonrpcServerLegacy.WithListener(legacyRPCMetrics)
 		synchronizer.WithListener(makeSyncMetrics(synchronizer, chain))
 		client.WithListener(makeFeederMetrics())
+		gatewayClient.WithListener(makeGatewayMetrics())
 		services = append(services, makeMetrics(cfg.MetricsHost, cfg.MetricsPort))
 	}
 	if cfg.GRPC {