f-21: mon: add prometheus data

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

pkg/prometheus/server.go

@@ -0,0 +1,20 @@
+package promserver
+
+import (
+	"log"
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"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) {
+	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))
+}