check if experimental is enabled during startup of client and server

cmd/kube-apiserver/app/server.go

@@ -35,7 +35,7 @@ import (
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/latest"
 	"k8s.io/kubernetes/pkg/api/meta"
-	explatest "k8s.io/kubernetes/pkg/apis/experimental/latest"
+	"k8s.io/kubernetes/pkg/api/registered"
 	"k8s.io/kubernetes/pkg/apiserver"
 	"k8s.io/kubernetes/pkg/capabilities"
 	client "k8s.io/kubernetes/pkg/client/unversioned"
@@ -331,6 +331,10 @@ func (s *APIServer) Run(_ []string) error {
 	// This takes preference over api/all, if specified.
 	enableExp := s.getRuntimeConfigValue("experimental/v1", false)
 
+	if enableExp && len(registered.GroupVersionsForGroup("experimental")) == 0 {
+		glog.Fatalf("experimental API is enabled in runtime config, but not registered throught environment variable KUBE_API_VERSIONS")
+	}
+
 	clientConfig := &client.Config{
 		Host:    net.JoinHostPort(s.InsecureBindAddress.String(), strconv.Itoa(s.InsecurePort)),
 		Version: s.StorageVersion,
@@ -344,9 +348,14 @@ func (s *APIServer) Run(_ []string) error {
 	if err != nil {
 		glog.Fatalf("Invalid storage version or misconfigured etcd: %v", err)
 	}
-	expEtcdStorage, err := newEtcd(s.EtcdConfigFile, s.EtcdServerList, latest.GroupOrDie("experimental").InterfacesFor, latest.GroupOrDie("experimental").Version, s.ExpStorageVersion, s.EtcdPathPrefix)
-	if err != nil {
-		glog.Fatalf("Invalid experimental storage version or misconfigured etcd: %v", err)
+
+	var expEtcdStorage storage.Interface
+	if enableExp {
+		expEtcdStorage, err = newEtcd(s.EtcdConfigFile, s.EtcdServerList, latest.GroupOrDie("experimental").InterfacesFor, latest.GroupOrDie("experimental").Version, s.ExpStorageVersion, s.EtcdPathPrefix)
+
+		if err != nil {
+			glog.Fatalf("Invalid experimental storage version or misconfigured etcd: %v", err)
+		}
 	}
 
 	n := s.ServiceClusterIPRange

pkg/client/unversioned/experimental.go

@@ -119,14 +119,20 @@ func NewExperimentalOrDie(c *Config) *ExperimentalClient {
 }
 
 func setExperimentalDefaults(config *Config) error {
+	// if experimental group is not registered, return an error
+	g, err := latest.Group("experimental")
+	if err != nil {
+		return err
+	}
 	config.Prefix = "/experimental"
 	if config.UserAgent == "" {
 		config.UserAgent = DefaultKubernetesUserAgent()
 	}
 	if config.Version == "" {
-		config.Version = latest.GroupOrDie("experimental").Version
+		config.Version = g.Version
 	}
-	versionInterfaces, err := latest.GroupOrDie("experimental").InterfacesFor(config.Version)
+
+	versionInterfaces, err := g.InterfacesFor(config.Version)
 	if err != nil {
 		return fmt.Errorf("Experimental API version '%s' is not recognized (valid values: %s)",
 			config.Version, strings.Join(latest.GroupOrDie("experimental").Versions, ", "))

pkg/client/unversioned/helper.go

@@ -33,6 +33,7 @@ import (
 	"github.com/golang/glog"
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/latest"
+	"k8s.io/kubernetes/pkg/api/registered"
 	"k8s.io/kubernetes/pkg/runtime"
 	"k8s.io/kubernetes/pkg/util"
 	"k8s.io/kubernetes/pkg/util/sets"
@@ -140,6 +141,10 @@ func New(c *Config) (*Client, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	if len(registered.GroupVersionsForGroup("experimental")) == 0 {
+		return &Client{RESTClient: client, ExperimentalClient: nil}, nil
+	}
 	experimentalConfig := *c
 	experimentalClient, err := NewExperimental(&experimentalConfig)
 	if err != nil {