Add ArgoCD version metric (argoproj#18852)

Signed-off-by: Omer Aplatony <omerap12@gmail.com>

server/metrics/metrics.go

@@ -9,6 +9,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 
+	"github.com/argoproj/argo-cd/v2/common"
 	"github.com/argoproj/argo-cd/v2/util/profile"
 )
 
@@ -18,6 +19,7 @@ type MetricsServer struct {
 	redisRequestHistogram    *prometheus.HistogramVec
 	extensionRequestCounter  *prometheus.CounterVec
 	extensionRequestDuration *prometheus.HistogramVec
+	argoVersion              *prometheus.GaugeVec
 }
 
 var (
@@ -51,6 +53,13 @@ var (
 		},
 		[]string{"extension"},
 	)
+	argoVersion = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "argocd_info",
+			Help: "ArgoCD version information",
+		},
+		[]string{"version"},
+	)
 )
 
 // NewMetricsServer returns a new prometheus server which collects api server metrics
@@ -61,12 +70,15 @@ func NewMetricsServer(host string, port int) *MetricsServer {
 		registry,
 		prometheus.DefaultGatherer,
 	}, promhttp.HandlerOpts{}))
+	argoVersion.WithLabelValues(common.GetVersion().Version).Set(1)
+
 	profile.RegisterProfiler(mux)
 
 	registry.MustRegister(redisRequestCounter)
 	registry.MustRegister(redisRequestHistogram)
 	registry.MustRegister(extensionRequestCounter)
 	registry.MustRegister(extensionRequestDuration)
+	registry.MustRegister(argoVersion)
 
 	return &MetricsServer{
 		Server: &http.Server{
@@ -77,6 +89,7 @@ func NewMetricsServer(host string, port int) *MetricsServer {
 		redisRequestHistogram:    redisRequestHistogram,
 		extensionRequestCounter:  extensionRequestCounter,
 		extensionRequestDuration: extensionRequestDuration,
+		argoVersion:              argoVersion,
 	}
 }