Improve rate limiter latency logging and metrics

Kubernetes-commit: 2bcf99f05fdc47fb4bc3601b9134408483f59773

tools/metrics/metrics.go

@@ -53,6 +53,8 @@ var (
 	ClientCertRotationAge DurationMetric = noopDuration{}
 	// RequestLatency is the latency metric that rest clients will update.
 	RequestLatency LatencyMetric = noopLatency{}
+	// RateLimiterLatency is the client side rate limiter latency metric.
+	RateLimiterLatency LatencyMetric = noopLatency{}
 	// RequestResult is the result metric that rest clients will update.
 	RequestResult ResultMetric = noopResult{}
 )
@@ -62,6 +64,7 @@ type RegisterOpts struct {
 	ClientCertExpiry      ExpiryMetric
 	ClientCertRotationAge DurationMetric
 	RequestLatency        LatencyMetric
+	RateLimiterLatency    LatencyMetric
 	RequestResult         ResultMetric
 }
 
@@ -78,6 +81,9 @@ func Register(opts RegisterOpts) {
 		if opts.RequestLatency != nil {
 			RequestLatency = opts.RequestLatency
 		}
+		if opts.RateLimiterLatency != nil {
+			RateLimiterLatency = opts.RateLimiterLatency
+		}
 		if opts.RequestResult != nil {
 			RequestResult = opts.RequestResult
 		}