Added number of namespaces metric

internal/server/monitoring.go

@@ -8,10 +8,16 @@ import (
 )
 
 var (
+	namespacesMetric = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "namespaces",
+		Help: "Number of namespaces",
+	})
+
 	displayListernersMetric = prometheus.NewGauge(prometheus.GaugeOpts{
 		Name: "display_listeners",
 		Help: "Active clients listening to /display",
 	})
+
 	counterMetric = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Name: "requests_total",
@@ -19,6 +25,7 @@ var (
 		},
 		[]string{"path", "code"},
 	)
+
 	durationMetric = prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
 			Name:    "requests_duration_seconds",
@@ -30,7 +37,7 @@ var (
 )
 
 func init() {
-	prometheus.MustRegister(displayListernersMetric, durationMetric, counterMetric)
+	prometheus.MustRegister(namespacesMetric, displayListernersMetric, counterMetric, durationMetric)
 }
 
 func monitoringMiddleware(handler string) func(next http.Handler) http.Handler {

internal/server/router.go

@@ -37,10 +37,15 @@ func GetRouter(useHostNamespace bool) *chi.Mux {
 		if !ok {
 			display = NewDisplay(namespace)
 			displays[namespace] = display
-
 		}
 		displaysMu.Unlock()
 
+		// We had to create a namespace
+		// Increase metric outside mutex for performance
+		if !ok {
+			namespacesMetric.Inc()
+		}
+
 		if r.Header.Get("Accept") == "text/event-stream" {
 			displayListernersMetric.Inc()
 			defer displayListernersMetric.Dec()