Initial commit

internal/service/monitoring/metrics.go

@@ -0,0 +1,95 @@
+package monitoring
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/gorilla/mux"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+
+	"payouts/internal/service/monitoring/config"
+)
+
+const (
+	METRICS_NAMESPACE = "payouts"
+)
+
+// Metrics represents the metrics service
+type Metrics interface {
+	GetMiddleware() func(next http.Handler) http.Handler
+}
+
+// metrics represents the metrics service implementation
+type metrics struct {
+	httpDuration prometheus.ObserverVec
+}
+
+// NewMetrics instantiates metrics service
+func NewMetrics(config config.Metrics) (Metrics, error) {
+	var httpDuration prometheus.ObserverVec
+	if config.Http.HistogramEnabled {
+		httpDuration = CreateHttpHistogram(config.Http.Buckets)
+	} else {
+		httpDuration = CreateHttpSummary(config.Http.Buckets)
+
+	}
+	return &metrics{
+		httpDuration: httpDuration,
+	}, nil
+}
+
+// GetMiddleware returns the middleware to be used in mux router
+func (m *metrics) GetMiddleware() func(next http.Handler) http.Handler {
+	return GetMiddleware(m.httpDuration)
+}
+
+func CreateHttpSummary(buckets []float64) *prometheus.SummaryVec {
+	return promauto.NewSummaryVec(prometheus.SummaryOpts{
+		Name: "http_server_requests_seconds",
+		Help: "Duration of HTTP requests.",
+	}, []string{"uri", "method", "code"})
+}
+
+func CreateHttpHistogram(buckets []float64) *prometheus.HistogramVec {
+	return promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Name:    "http_server_requests_seconds",
+		Help:    "Duration of HTTP requests.",
+		Buckets: buckets,
+	}, []string{"uri", "method", "code"})
+
+}
+
+func GetMiddleware(histogramVec prometheus.ObserverVec) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			route := mux.CurrentRoute(r)
+			path, _ := route.GetPathTemplate()
+			wd := &writerDelegate{
+				ResponseWriter: w,
+				statusCode:     http.StatusOK,
+			}
+
+			start := time.Now()
+			defer func() {
+				duration := time.Since(start).Seconds()
+				code := strconv.Itoa(wd.statusCode)
+				histogramVec.WithLabelValues(path, r.Method, code).Observe(duration)
+			}()
+
+			next.ServeHTTP(wd, r)
+		})
+	}
+}
+
+type writerDelegate struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+// override the WriteHeader method
+func (w *writerDelegate) WriteHeader(statusCode int) {
+	w.statusCode = statusCode
+	w.ResponseWriter.WriteHeader(statusCode)
+}