fix: register k8s metrics

controller-runtime also calls `metrics.Register()` during init and this
function can be called only once. To ensure that the k8s client metrics
get updated, the global variables need to be set again by the operator.

https://github.com/kubernetes-sigs/controller-runtime/blob/67b27f27e514bd9ac4cf9a2d84dec089ece95bf7/pkg/metrics/client_go_adapter.go#L42-L55
https://github.com/kubernetes/client-go/blob/aa7909e7d7c0661792ba21b9e882f3cd6ad0ce53/tools/metrics/metrics.go#L129-L170

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

pkg/k8sutil/metrics.go

@@ -28,10 +28,15 @@ type clientGoHTTPMetricAdapter struct {
 	duration *prometheus.SummaryVec
 }
 
+var _ = metrics.LatencyMetric(&clientGoHTTPMetricAdapter{})
+var _ = metrics.ResultMetric(&clientGoHTTPMetricAdapter{})
+
 type clientGoRateLimiterMetricAdapter struct {
 	duration *prometheus.SummaryVec
 }
 
+var _ = metrics.LatencyMetric(&clientGoRateLimiterMetricAdapter{})
+
 // MustRegisterClientGoMetrics registers k8s.io/client-go metrics.
 // It panics if it encounters an error (e.g. metrics already registered).
 func MustRegisterClientGoMetrics(registerer prometheus.Registerer) {
@@ -64,13 +69,23 @@ func MustRegisterClientGoMetrics(registerer prometheus.Registerer) {
 		),
 	}
 
+	// controller-runtime also calls metrics.Register() during init and this
+	// function can be called only once. To ensure that the k8s client metrics
+	// get updated, the global variables need to be set again here.
+	//
+	// Details:
+	// https://github.com/kubernetes-sigs/controller-runtime/blob/67b27f27e514bd9ac4cf9a2d84dec089ece95bf7/pkg/metrics/client_go_adapter.go#L42-L55
+	// https://github.com/kubernetes/client-go/blob/aa7909e7d7c0661792ba21b9e882f3cd6ad0ce53/tools/metrics/metrics.go#L129-L170
 	metrics.Register(
 		metrics.RegisterOpts{
 			RequestLatency:     httpMetrics,
 			RequestResult:      httpMetrics,
 			RateLimiterLatency: rateLimiterMetrics,
 		},
 	)
+	metrics.RequestLatency = httpMetrics
+	metrics.RequestResult = httpMetrics
+	metrics.RateLimiterLatency = rateLimiterMetrics
 
 	registerer.MustRegister(httpMetrics.count, httpMetrics.duration, rateLimiterMetrics.duration)
 }