From 29b59bb85e55853ded451e1b9213af9145bc7b8f Mon Sep 17 00:00:00 2001
From: Josh Klopfenstein <git@joshklop.com>
Date: Tue, 12 Dec 2023 16:40:22 -0600
Subject: [PATCH] Add feeder metrics (#1543)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Ömer Faruk Irmak <omerfirmak@gmail.com>
---
 clients/feeder/event_listener.go | 17 +++++++++++++++++
 clients/feeder/feeder.go         |  9 +++++++++
 clients/feeder/feeder_test.go    | 15 +++++++++++++++
 node/metrics.go                  | 17 +++++++++++++++++
 node/node.go                     |  1 +
 5 files changed, 59 insertions(+)
 create mode 100644 clients/feeder/event_listener.go

diff --git a/clients/feeder/event_listener.go b/clients/feeder/event_listener.go
new file mode 100644
index 0000000000..d5298ee0de
--- /dev/null
+++ b/clients/feeder/event_listener.go
@@ -0,0 +1,17 @@
+package feeder
+
+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)
+	}
+}
diff --git a/clients/feeder/feeder.go b/clients/feeder/feeder.go
index 58033c13e9..8bfb297745 100644
--- a/clients/feeder/feeder.go
+++ b/clients/feeder/feeder.go
@@ -30,6 +30,12 @@ type Client struct {
 	minWait    time.Duration
 	log        utils.SimpleLogger
 	userAgent  string
+	listener   EventListener
+}
+
+func (c *Client) WithListener(l EventListener) *Client {
+	c.listener = l
+	return c
 }
 
 func (c *Client) WithBackoff(b Backoff) *Client {
@@ -185,6 +191,7 @@ func NewClient(clientURL string) *Client {
 		maxWait:    4 * time.Second,
 		minWait:    time.Second,
 		log:        utils.NewNopZapLogger(),
+		listener:   &SelectiveListener{},
 	}
 }
 
@@ -225,8 +232,10 @@ func (c *Client) get(ctx context.Context, queryURL string) (io.ReadCloser, error
 				req.Header.Set("User-Agent", c.userAgent)
 			}
 
+			reqTimer := time.Now()
 			res, err = c.client.Do(req)
 			if err == nil {
+				c.listener.OnResponse(req.URL.Path, res.StatusCode, time.Since(reqTimer))
 				if res.StatusCode == http.StatusOK {
 					return res.Body, nil
 				} else {
diff --git a/clients/feeder/feeder_test.go b/clients/feeder/feeder_test.go
index cc88032e1d..087fde339d 100644
--- a/clients/feeder/feeder_test.go
+++ b/clients/feeder/feeder_test.go
@@ -7,6 +7,7 @@ import (
 	"net/http/httptest"
 	"strconv"
 	"testing"
+	"time"
 
 	"github.com/NethermindEth/juno/clients/feeder"
 	"github.com/NethermindEth/juno/core/felt"
@@ -624,3 +625,17 @@ func TestBlockTrace(t *testing.T) {
 		require.Len(t, trace.Traces, 2)
 	})
 }
+
+func TestEventListener(t *testing.T) {
+	isCalled := false
+	client := feeder.NewTestClient(t, utils.Integration).WithListener(&feeder.SelectiveListener{
+		OnResponseCb: func(urlPath string, status int, _ time.Duration) {
+			isCalled = true
+			require.Equal(t, 200, status)
+			require.Equal(t, "/get_block", urlPath)
+		},
+	})
+	_, err := client.Block(context.Background(), "0")
+	require.NoError(t, err)
+	require.True(t, isCalled)
+}
diff --git a/node/metrics.go b/node/metrics.go
index 6afdf2bdb8..bbd99ca243 100644
--- a/node/metrics.go
+++ b/node/metrics.go
@@ -2,9 +2,11 @@ package node
 
 import (
 	"math"
+	"strconv"
 	"time"
 
 	"github.com/NethermindEth/juno/blockchain"
+	"github.com/NethermindEth/juno/clients/feeder"
 	"github.com/NethermindEth/juno/core"
 	"github.com/NethermindEth/juno/db"
 	"github.com/NethermindEth/juno/jsonrpc"
@@ -228,3 +230,18 @@ func makeL1Metrics() l1.EventListener {
 		},
 	}
 }
+
+func makeFeederMetrics() feeder.EventListener {
+	requestLatencies := prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "feeder",
+		Subsystem: "client",
+		Name:      "request_latency",
+	}, []string{"method", "status"})
+	prometheus.MustRegister(requestLatencies)
+	return &feeder.SelectiveListener{
+		OnResponseCb: func(urlPath string, status int, took time.Duration) {
+			statusString := strconv.FormatInt(int64(status), 10)
+			requestLatencies.WithLabelValues(urlPath, statusString).Observe(took.Seconds())
+		},
+	}
+}
diff --git a/node/node.go b/node/node.go
index 1a22e8acbc..3835dbbd5d 100644
--- a/node/node.go
+++ b/node/node.go
@@ -176,6 +176,7 @@ func New(cfg *Config, version string) (*Node, error) { //nolint:gocyclo,funlen
 		jsonrpcServer.WithListener(rpcMetrics)
 		jsonrpcServerLegacy.WithListener(legacyRPCMetrics)
 		synchronizer.WithListener(makeSyncMetrics(synchronizer, chain))
+		client.WithListener(makeFeederMetrics())
 		services = append(services, makeMetrics(cfg.MetricsHost, cfg.MetricsPort))
 	}
 	if cfg.GRPC {