chore(exporter): rework exporter to fix wrong histogram usage and cache metric data

internal/exporter/middleware.go

@@ -2,67 +2,19 @@ package exporter
 
 import (
 	"net/http"
-	"sync"
-	"time"
 
-	"github.com/go-chi/chi/v5/middleware"
+	"github.com/prometheus/client_golang/prometheus"
 )
 
-type RequestData struct {
-	Latency time.Duration
-	Request *http.Request
-	Start   time.Time
-}
-
-type RequestDataQueue struct {
-	mu   sync.Mutex
-	data []RequestData
-}
-
-func NewRequestDataQueue() *RequestDataQueue {
-	return &RequestDataQueue{
-		data: []RequestData{},
-	}
-}
-
-func (q *RequestDataQueue) Add(data RequestData) {
-	q.mu.Lock()
-	defer q.mu.Unlock()
-	q.data = append(q.data, data)
-}
-
-func (q *RequestDataQueue) ConsumeAll() []RequestData {
-	q.mu.Lock()
-	defer q.mu.Unlock()
-	data := q.data
-	q.data = nil
-	return data
-}
-
 type Middleware struct {
-	queue *RequestDataQueue
-}
-
-func NewMiddleware(queue *RequestDataQueue) func(next http.Handler) http.Handler {
-	m := Middleware{
-		queue: queue,
-	}
-	return m.handler
+	metrics *Metrics
 }
 
 func (m Middleware) handler(next http.Handler) http.Handler {
-	fn := func(w http.ResponseWriter, r *http.Request) {
-		start := time.Now()
-		ww := middleware.NewWrapResponseWriter(w, r.ProtoMajor)
-		next.ServeHTTP(ww, r)
-
-		m.queue.Add(
-			RequestData{
-				Latency: time.Since(start),
-				Request: r,
-				Start:   start,
-			},
-		)
-	}
-	return http.HandlerFunc(fn)
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		timer := prometheus.NewTimer(m.metrics.metricRequestLatency)
+		next.ServeHTTP(w, r)
+		m.metrics.metricRequestsTotal.Inc()
+		timer.ObserveDuration()
+	})
 }