feat: add basic prometheus metrics integration

internal/proxy/server.go

@@ -15,6 +15,7 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/pkg/errors"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"gitlab.com/wpetit/goweb/logger"
 )
 
@@ -84,18 +85,40 @@ func (s *Server) run(parentCtx context.Context, addrs chan net.Addr, errs chan e
 	)
 
 	router.Use(middleware.RequestLogger(bouncerChi.NewLogFormatter()))
-	router.Use(director.Middleware())
 
-	handler := proxy.New(
-		proxy.WithRequestTransformers(
-			director.RequestTransformer(),
-		),
-		proxy.WithResponseTransformers(
-			director.ResponseTransformer(),
-		),
-	)
+	if s.serverConfig.Metrics.Enabled {
+		metrics := s.serverConfig.Metrics
 
-	router.Handle("/*", handler)
+		logger.Info(ctx, "enabling metrics", logger.F("endpoint", metrics.Endpoint))
+
+		router.Group(func(r chi.Router) {
+			if metrics.BasicAuth != nil {
+				logger.Info(ctx, "enabling authentication on metrics endpoint")
+
+				r.Use(middleware.BasicAuth(
+					"metrics",
+					metrics.BasicAuth.CredentialsMap(),
+				))
+			}
+
+			r.Handle(string(metrics.Endpoint), promhttp.Handler())
+		})
+	}
+
+	router.Group(func(r chi.Router) {
+		r.Use(director.Middleware())
+
+		handler := proxy.New(
+			proxy.WithRequestTransformers(
+				director.RequestTransformer(),
+			),
+			proxy.WithResponseTransformers(
+				director.ResponseTransformer(),
+			),
+		)
+
+		r.Handle("/*", handler)
+	})
 
 	if err := http.Serve(listener, router); err != nil && !errors.Is(err, net.ErrClosed) {
 		errs <- errors.WithStack(err)