TUN-5703: Add prometheus metric for current configuration version

Author: DevinCarr

orchestration/metrics.go

@@ -0,0 +1,25 @@
+package orchestration
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+	MetricsNamespace = "cloudflared"
+	MetricsSubsystem = "orchestration"
+)
+
+var (
+	configVersion = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Namespace: MetricsNamespace,
+			Subsystem: MetricsSubsystem,
+			Name:      "config_version",
+			Help:      "Configuration Version",
+		},
+	)
+)
+
+func init() {
+	prometheus.MustRegister(configVersion)
+}

orchestration/orchestrator.go

@@ -95,6 +95,7 @@ func (o *Orchestrator) UpdateConfig(version int32, config []byte) *tunnelpogs.Up
 		Int32("version", version).
 		Str("config", string(config)).
 		Msg("Updated to new configuration")
+	configVersion.Set(float64(version))
 	return &tunnelpogs.UpdateConfigurationResponse{
 		LastAppliedVersion: o.currentVersion,
 	}