feat: reimplemntation of metrics

remove response_status_total counter
rework http_requests_total
move server to internal package
expose pkg handlers from server sub-package
move server handlers in handlers sub-package

cmd/start.go

@@ -1,8 +1,8 @@
 package cmd
 
 import (
+	"okp4/cosmos-faucet/internal/server"
 	"okp4/cosmos-faucet/pkg/client"
-	"okp4/cosmos-faucet/pkg/server"
 
 	"github.com/rs/zerolog/log"
 	"github.com/spf13/cobra"
@@ -30,8 +30,7 @@ func NewStartCommand() *cobra.Command {
 				log.Info().Msg("Server stopped")
 			}(faucet)
 
-			httpServer := server.NewServer(faucet)
-			httpServer.Start(addr)
+			server.NewServer(faucet).Start(addr)
 		},
 	}
 

internal/server/handlers/health.go

@@ -0,0 +1,18 @@
+package handlers
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/rs/zerolog/log"
+)
+
+// NewHealthRequestHandlerFunc only returns 200 OK to check app status.
+func NewHealthRequestHandlerFunc() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		if _, err := w.Write([]byte("")); err != nil {
+			log.Error().Msg(fmt.Sprintf("Error while sending health response: %v", err))
+		}
+	}
+}

internal/server/handlers/prometheus.go

@@ -0,0 +1,64 @@
+package handlers
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/gorilla/mux"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+type responseWriter struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func newResponseWriter(w http.ResponseWriter) *responseWriter {
+	return &responseWriter{w, http.StatusOK}
+}
+
+// PrometheusMiddleware adds prometheus metrics on every request to a router.
+func PrometheusMiddleware(handler http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		route := mux.CurrentRoute(r)
+		path, _ := route.GetPathTemplate()
+		methods, _ := route.GetMethods()
+
+		timer := prometheus.NewTimer(httpDuration.WithLabelValues(path))
+
+		rw := newResponseWriter(w)
+		handler.ServeHTTP(rw, r)
+
+		statusCode := rw.statusCode
+
+		totalRequests.WithLabelValues(methods[0], path, strconv.Itoa(statusCode)).Inc()
+		timer.ObserveDuration()
+	})
+}
+
+// NewMetricsRequestHandler exposes prometheus metrics.
+func NewMetricsRequestHandler() http.Handler {
+	return promhttp.Handler()
+}
+
+func (rw *responseWriter) WriteHeader(code int) {
+	rw.statusCode = code
+	rw.ResponseWriter.WriteHeader(code)
+}
+
+var totalRequests = promauto.NewCounterVec(
+	prometheus.CounterOpts{
+		Name: "http_requests_total",
+		Help: "HTTP requests counter.",
+	}, []string{"method", "path", "code"},
+)
+
+var httpDuration = promauto.NewHistogramVec(
+	prometheus.HistogramOpts{
+		Name: "http_request_duration_seconds",
+		Help: "Duration of HTTP requests.",
+	},
+	[]string{"path"},
+)

internal/server/router.go

@@ -0,0 +1,21 @@
+package server
+
+import (
+	"okp4/cosmos-faucet/internal/server/handlers"
+	"okp4/cosmos-faucet/pkg/client"
+	"okp4/cosmos-faucet/pkg/server"
+)
+
+func (s *httpServer) createRoutes(faucet *client.Faucet) {
+	s.router.Use(handlers.PrometheusMiddleware)
+	s.router.Path("/").
+		Queries("address", "{address}").
+		HandlerFunc(server.NewSendRequestHandlerFn(faucet)).
+		Methods("GET")
+	s.router.Path("/health").
+		HandlerFunc(handlers.NewHealthRequestHandlerFunc()).
+		Methods("GET")
+	s.router.Path("/metrics").
+		Handler(handlers.NewMetricsRequestHandler()).
+		Methods("GET")
+}

pkg/server/server.go → internal/server/server.go

@@ -2,7 +2,6 @@ package server
 
 import (
 	"net/http"
-
 	"okp4/cosmos-faucet/pkg/client"
 
 	"github.com/gorilla/mux"
@@ -24,7 +23,6 @@ func NewServer(faucet *client.Faucet) HTTPServer {
 		router: mux.NewRouter().StrictSlash(true),
 	}
 	server.createRoutes(faucet)
-	initPrometheus()
 	return server
 }
 

pkg/server/send.go

@@ -10,7 +10,8 @@ import (
 	"github.com/rs/zerolog/log"
 )
 
-func newSendRequestHandlerFn(faucet *client.Faucet) http.HandlerFunc {
+// NewSendRequestHandlerFn returns an HTTP REST handler for make transaction to a given address.
+func NewSendRequestHandlerFn(faucet *client.Faucet) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		vars := mux.Vars(r)
 		bech32Addr := vars["address"]