Make command-line flag --feature-gates compatible

cmd/kube-proxy/app/server.go

@@ -39,6 +39,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/apiserver/pkg/server/healthz"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
+	"k8s.io/apiserver/pkg/util/flag"
 	clientgoclientset "k8s.io/client-go/kubernetes"
 	v1core "k8s.io/client-go/kubernetes/typed/core/v1"
 	"k8s.io/client-go/rest"
@@ -166,7 +167,8 @@ func AddFlags(options *Options, fs *pflag.FlagSet) {
 		"NAT timeout for TCP connections in the CLOSE_WAIT state")
 	fs.BoolVar(&options.config.EnableProfiling, "profiling", options.config.EnableProfiling, "If true enables profiling via web interface on /debug/pprof handler.")
 	fs.StringVar(&options.config.IPVS.Scheduler, "ipvs-scheduler", options.config.IPVS.Scheduler, "The ipvs scheduler type when proxy mode is ipvs")
-	utilfeature.DefaultFeatureGate.AddFlag(fs)
+	fs.Var(flag.NewMapStringBool(&options.config.FeatureGates), "feature-gates", "A set of key=value pairs that describe feature gates for alpha/experimental features. "+
+		"Options are:\n"+strings.Join(utilfeature.DefaultFeatureGate.KnownFeatures(), "\n"))
 }
 
 func NewOptions() *Options {
@@ -192,11 +194,14 @@ func (o *Options) Complete() error {
 			return err
 		} else {
 			o.config = c
-			// Make sure we apply the feature gate settings in the config file.
-			utilfeature.DefaultFeatureGate.SetFromMap(o.config.FeatureGates)
 		}
 	}
 
+	err := utilfeature.DefaultFeatureGate.SetFromMap(o.config.FeatureGates)
+	if err != nil {
+		return err
+	}
+
 	return nil
 }