feat: prometheus metrics

go.mod

@@ -11,4 +11,17 @@ require (
 	github.com/lmittmann/tint v1.0.7
 )
 
-require github.com/cespare/xxhash/v2 v2.3.0 // indirect
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.62.0 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	golang.org/x/sys v0.30.0 // indirect
+	google.golang.org/protobuf v1.36.5 // indirect
+)
+
+require (
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/prometheus/client_golang v1.22.0
+)

go.sum

@@ -1,3 +1,5 @@
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/go-chi/chi/v5 v5.1.0 h1:acVI1TYaD+hhedDJ3r54HyA6sExp3HfXq7QWEEY/xMw=
@@ -18,5 +20,19 @@ github.com/lmittmann/tint v1.0.6 h1:vkkuDAZXc0EFGNzYjWcV0h7eEX+uujH48f/ifSkJWgc=
 github.com/lmittmann/tint v1.0.6/go.mod h1:HIS3gSy7qNwGCj+5oRjAutErFBl4BzdQP6cJZ0NfMwE=
 github.com/lmittmann/tint v1.0.7 h1:D/0OqWZ0YOGZ6AyC+5Y2kD8PBEzBk6rFHVSfOqCkF9Y=
 github.com/lmittmann/tint v1.0.7/go.mod h1:HIS3gSy7qNwGCj+5oRjAutErFBl4BzdQP6cJZ0NfMwE=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
+github.com/prometheus/client_golang v1.22.0 h1:rb93p9lokFEsctTys46VnV1kLCDpVZ0a/Y92Vm0Zc6Q=
+github.com/prometheus/client_golang v1.22.0/go.mod h1:R7ljNsLXhuQXYZYtw6GAE9AZg8Y7vEW5scdCXrWRXC0=
+github.com/prometheus/client_model v0.6.1 h1:ZKSh/rekM+n3CeS952MLRAdFwIKqeY8b62p8ais2e9E=
+github.com/prometheus/client_model v0.6.1/go.mod h1:OrxVMOVHjw3lKMa8+x6HeMGkHMQyHDk9E3jmP2AmGiY=
+github.com/prometheus/common v0.62.0 h1:xasJaQlnWAeyHdUBeGjXmutelfJHWMRr+Fg4QszZ2Io=
+github.com/prometheus/common v0.62.0/go.mod h1:vyBcEuLSvWos9B1+CyL7JZ2up+uFzXhkqml0W5zIY1I=
+github.com/prometheus/procfs v0.15.1 h1:YagwOFzUgYfKKHX6Dr+sHT7km/hxC76UB0learggepc=
+github.com/prometheus/procfs v0.15.1/go.mod h1:fB45yRUv8NstnjriLhBQLuOUt+WW4BsoGhij/e3PBqk=
 golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+google.golang.org/protobuf v1.36.5 h1:tPhr+woSbjfYvY6/GPufUoYizxw1cF/yFoxJ2fmpwlM=
+google.golang.org/protobuf v1.36.5/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=

internal/middleware/prometheus.go

@@ -0,0 +1,58 @@
+package middleware
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var (
+	httpRequestsTotal = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "http_requests_total",
+			Help: "Total number of HTTP requests",
+		},
+		[]string{"method", "path", "status"},
+	)
+
+	httpRequestDuration = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Name:    "http_request_duration_seconds",
+			Help:    "Duration of HTTP requests",
+			Buckets: prometheus.DefBuckets,
+		},
+		[]string{"method", "path", "status"},
+	)
+)
+
+func init() {
+	prometheus.MustRegister(httpRequestsTotal, httpRequestDuration)
+}
+
+func PrometheusMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+		rr := &responseRecorder{ResponseWriter: w, statusCode: 200}
+		next.ServeHTTP(rr, r)
+		duration := time.Since(start)
+
+		method := r.Method
+		path := r.URL.Path
+		status := strconv.Itoa(rr.statusCode)
+
+		httpRequestsTotal.WithLabelValues(method, path, status).Inc()
+		httpRequestDuration.WithLabelValues(method, path, status).Observe(duration.Seconds())
+	})
+}
+
+type responseRecorder struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func (rr *responseRecorder) WriteHeader(code int) {
+	rr.statusCode = code
+	rr.ResponseWriter.WriteHeader(code)
+}

internal/server/router.go

@@ -11,8 +11,10 @@ import (
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/go-chi/cors"
 	"github.com/go-chi/httprate"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 
 	"api/internal/handler"
+	app_middleware "api/internal/middleware"
 )
 
 func getAllowedOrigins() []string {
@@ -29,6 +31,7 @@ func NewRouter() {
 	r := chi.NewRouter()
 
 	// Middleware
+	r.Use(app_middleware.PrometheusMiddleware)
 	r.Use(middleware.RequestID)
 	r.Use(middleware.RealIP)
 	r.Use(middleware.Logger)
@@ -43,6 +46,9 @@ func NewRouter() {
 		MaxAge:         300,
 	}))
 
+	// Prometheus
+	r.Handle("/metrics", promhttp.Handler())
+
 	r.Get("/", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		json.NewEncoder(w).Encode(map[string]string{