Implemented admin pane + user permission

internal/metrics/metrics.go

@@ -38,6 +38,30 @@ func IncWrites() { writeOps.Add(1) }
 // IncHistoryReqs increments the history request counter.
 func IncHistoryReqs() { historyReqs.Add(1) }
 
+// Stats is a point-in-time snapshot of the in-process counters, for rendering
+// as JSON in the admin pane (the Prometheus Handler renders the same data as
+// text).
+type Stats struct {
+	UptimeSeconds float64 `json:"uptimeSeconds"`
+	WsConnections int64   `json:"wsConnections"`
+	MsgIn         int64   `json:"msgIn"`
+	MsgOut        int64   `json:"msgOut"`
+	WriteOps      int64   `json:"writeOps"`
+	HistoryReqs   int64   `json:"historyReqs"`
+}
+
+// Snapshot returns the current values of all counters and gauges.
+func Snapshot() Stats {
+	return Stats{
+		UptimeSeconds: time.Since(startTime).Seconds(),
+		WsConnections: wsConns.Load(),
+		MsgIn:         msgIn.Load(),
+		MsgOut:        msgOut.Load(),
+		WriteOps:      writeOps.Load(),
+		HistoryReqs:   historyReqs.Load(),
+	}
+}
+
 // Handler returns an http.HandlerFunc that renders Prometheus-format metrics.
 // activeSubs is called each request to read the current number of unique signal
 // subscriptions from the broker; pass nil to omit the metric.