feat: prometheus metrics

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/gorilla/mux v1.8.0
 	github.com/rs/zerolog v1.26.1
 	github.com/smartystreets/goconvey v1.7.2
+	github.com/prometheus/client_golang v1.12.1
 	github.com/spf13/cobra v1.4.0
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.11.0
@@ -77,7 +78,6 @@ require (
 	github.com/petermattis/goid v0.0.0-20180202154549-b0b1615b78e5 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/prometheus/client_golang v1.12.1 // indirect
 	github.com/prometheus/client_model v0.2.0 // indirect
 	github.com/prometheus/common v0.32.1 // indirect
 	github.com/prometheus/procfs v0.7.3 // indirect

pkg/server/health.go

@@ -0,0 +1,11 @@
+package server
+
+import "net/http"
+
+// NewHealthRequestHandlerFunc returns a REST handler func to check app status
+func NewHealthRequestHandlerFunc() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(""))
+	}
+}

pkg/server/prometheus.go

@@ -1,22 +1,90 @@
 package server
 
 import (
-    "context"
-    "net/http"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"net/http"
+	"strconv"
 
-    "okp4/cosmos-faucet/pkg/client"
+	"github.com/gorilla/mux"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
-// NewHealthRequestHandlerFunc returns a REST handler func to check app status
-func NewHealthRequestHandlerFunc() http.HandlerFunc {
-    return func(w http.ResponseWriter, r *http.Request) {
-        w.WriteHeader(http.StatusOK)
-        _, _ = w.Write([]byte(""))
-    }
+type responseWriter struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func newResponseWriter(w http.ResponseWriter) *responseWriter {
+	return &responseWriter{w, http.StatusOK}
+}
+
+func (rw *responseWriter) WriteHeader(code int) {
+	rw.statusCode = code
+	rw.ResponseWriter.WriteHeader(code)
+}
+
+type prometheusHandler struct {
+	totalRequests  *prometheus.CounterVec
+	responseStatus *prometheus.CounterVec
+	httpDuration   *prometheus.HistogramVec
+}
+
+func (p prometheusHandler) init() {
+	_ = prometheus.Register(p.totalRequests)
+	_ = prometheus.Register(p.responseStatus)
+	_ = prometheus.Register(p.httpDuration)
+}
+
+func newPrometheusHandler() prometheusHandler {
+	handler := prometheusHandler{
+		totalRequests: prometheus.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "http_requests_total",
+				Help: "Number of get requests.",
+			}, []string{"path"},
+		),
+		responseStatus: prometheus.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "response_status",
+				Help: "Status of HTTP response",
+			},
+			[]string{"status"},
+		),
+		httpDuration: promauto.NewHistogramVec(prometheus.HistogramOpts{
+			Name: "http_response_time_seconds",
+			Help: "Duration of HTTP requests.",
+		}, []string{"path"}),
+	}
+	handler.init()
+	return handler
+}
+
+func prometheusMiddleware(handler http.Handler) http.Handler {
+	promHandler := newPrometheusHandler()
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		route := mux.CurrentRoute(r)
+		path, _ := route.GetPathTemplate()
+
+		timer := prometheus.NewTimer(promHandler.httpDuration.WithLabelValues(path))
+
+		rw := newResponseWriter(w)
+		handler.ServeHTTP(rw, r)
+
+		statusCode := rw.statusCode
+
+		if !(path == "/metrics" || path == "/health") {
+			promHandler.responseStatus.WithLabelValues(strconv.Itoa(statusCode)).Inc()
+			promHandler.totalRequests.WithLabelValues(path).Inc()
+			timer.ObserveDuration()
+		}
+	})
 }
 
 // NewMetricsRequestHandlerFunc returns a REST handler func returning useful prometheus metrics
-func NewMetricsRequestHandlerFunc(ctx context.Context, faucet *client.Faucet) http.HandlerFunc {
-    return func(w http.ResponseWriter, r *http.Request) {
-    }
+func NewMetricsRequestHandlerFunc() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		promhttp.Handler()
+	}
 }

pkg/server/router.go

@@ -7,6 +7,7 @@ import (
 )
 
 func (s httpServer) createRoutes(faucet *client.Faucet) {
+	s.router.Use(prometheusMiddleware)
 	s.router.Path("/").
 		Queries("address", "{address}").
 		HandlerFunc(NewSendRequestHandlerFn(context.Background(), faucet)).
@@ -15,6 +16,6 @@ func (s httpServer) createRoutes(faucet *client.Faucet) {
 		HandlerFunc(NewHealthRequestHandlerFunc()).
 		Methods("GET")
 	s.router.Path("/metrics").
-		HandlerFunc(NewMetricsRequestHandlerFunc(context.Background(), faucet)).
+		HandlerFunc(NewMetricsRequestHandlerFunc()).
 		Methods("GET")
 }