f-29: stop: add a proper stop

Signed-off-by: GnomeZworc <nicolas.boufidjeline@g3e.fr>

pkg/prometheus/server.go

@@ -1,6 +1,8 @@
 package promserver
 
 import (
+	"context"
+	"errors"
 	"log"
 	"net/http"
 
@@ -8,13 +10,30 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
-// Start launches the Prometheus metrics HTTP server on the given address.
-// The provided registry is used to expose metrics at /metrics.
-func Start(address string, registry *prometheus.Registry) {
+// Server exposes the Prometheus metrics endpoint.
+type Server struct {
+	srv *http.Server
+}
+
+// New builds the metrics server for the given address and registry.
+func New(address string, registry *prometheus.Registry) *Server {
 	mux := http.NewServeMux()
 	mux.Handle("/metrics", promhttp.HandlerFor(registry, promhttp.HandlerOpts{
 		EnableOpenMetrics: true,
 	}))
-	log.Printf("Prometheus server listening on %s", address)
-	log.Fatal(http.ListenAndServe(address, mux))
+	return &Server{srv: &http.Server{Addr: address, Handler: mux}}
+}
+
+// Start blocks until the server stops. A failure is logged, never fatal: an
+// unavailable metrics endpoint must not bring the whole agent down.
+func (s *Server) Start() {
+	log.Printf("Prometheus server listening on %s", s.srv.Addr)
+	if err := s.srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+		log.Printf("Prometheus server stopped: %v", err)
+	}
+}
+
+// Shutdown stops the server, waiting for in-flight requests until ctx expires.
+func (s *Server) Shutdown(ctx context.Context) error {
+	return s.srv.Shutdown(ctx)
 }