diff --git a/metrics-server/vendor/k8s.io/apiserver/pkg/endpoints/discovery/root.go b/metrics-server/vendor/k8s.io/apiserver/pkg/endpoints/discovery/root.go
new file mode 100644
index 0000000..7ed64a9
--- /dev/null
+++ b/metrics-server/vendor/k8s.io/apiserver/pkg/endpoints/discovery/root.go
@@ -0,0 +1,135 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package discovery
+
+import (
+	"net/http"
+	"sync"
+
+	restful "github.com/emicklei/go-restful"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	utilnet "k8s.io/apimachinery/pkg/util/net"
+	"k8s.io/apiserver/pkg/endpoints/handlers/negotiation"
+	"k8s.io/apiserver/pkg/endpoints/handlers/responsewriters"
+)
+
+// GroupManager is an interface that allows dynamic mutation of the existing webservice to handle
+// API groups being added or removed.
+type GroupManager interface {
+	AddGroup(apiGroup metav1.APIGroup)
+	RemoveGroup(groupName string)
+
+	WebService() *restful.WebService
+}
+
+// rootAPIsHandler creates a webservice serving api group discovery.
+// The list of APIGroups may change while the server is running because additional resources
+// are registered or removed.  It is not safe to cache the values.
+type rootAPIsHandler struct {
+	// addresses is used to build cluster IPs for discovery.
+	addresses Addresses
+
+	serializer runtime.NegotiatedSerializer
+
+	// Map storing information about all groups to be exposed in discovery response.
+	// The map is from name to the group.
+	lock      sync.RWMutex
+	apiGroups map[string]metav1.APIGroup
+	// apiGroupNames preserves insertion order
+	apiGroupNames []string
+}
+
+func NewRootAPIsHandler(addresses Addresses, serializer runtime.NegotiatedSerializer) *rootAPIsHandler {
+	// Because in release 1.1, /apis returns response with empty APIVersion, we
+	// use stripVersionNegotiatedSerializer to keep the response backwards
+	// compatible.
+	serializer = stripVersionNegotiatedSerializer{serializer}
+
+	return &rootAPIsHandler{
+		addresses:  addresses,
+		serializer: serializer,
+		apiGroups:  map[string]metav1.APIGroup{},
+	}
+}
+
+func (s *rootAPIsHandler) AddGroup(apiGroup metav1.APIGroup) {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	_, alreadyExists := s.apiGroups[apiGroup.Name]
+
+	s.apiGroups[apiGroup.Name] = apiGroup
+	if !alreadyExists {
+		s.apiGroupNames = append(s.apiGroupNames, apiGroup.Name)
+	}
+}
+
+func (s *rootAPIsHandler) RemoveGroup(groupName string) {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	delete(s.apiGroups, groupName)
+	for i := range s.apiGroupNames {
+		if s.apiGroupNames[i] == groupName {
+			s.apiGroupNames = append(s.apiGroupNames[:i], s.apiGroupNames[i+1:]...)
+			break
+		}
+	}
+}
+
+func (s *rootAPIsHandler) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+
+	orderedGroups := []metav1.APIGroup{}
+	for _, groupName := range s.apiGroupNames {
+		orderedGroups = append(orderedGroups, s.apiGroups[groupName])
+	}
+
+	clientIP := utilnet.GetClientIP(req)
+	serverCIDR := s.addresses.ServerAddressByClientCIDRs(clientIP)
+	groups := make([]metav1.APIGroup, len(orderedGroups))
+	for i := range orderedGroups {
+		groups[i] = orderedGroups[i]
+		groups[i].ServerAddressByClientCIDRs = serverCIDR
+	}
+
+	responsewriters.WriteObjectNegotiated(s.serializer, schema.GroupVersion{}, resp, req, http.StatusOK, &metav1.APIGroupList{Groups: groups})
+}
+
+func (s *rootAPIsHandler) restfulHandle(req *restful.Request, resp *restful.Response) {
+	s.ServeHTTP(resp.ResponseWriter, req.Request)
+}
+
+// WebService returns a webservice serving api group discovery.
+// Note: during the server runtime apiGroups might change.
+func (s *rootAPIsHandler) WebService() *restful.WebService {
+	mediaTypes, _ := negotiation.MediaTypesForSerializer(s.serializer)
+	ws := new(restful.WebService)
+	ws.Path(APIGroupPrefix)
+	ws.Doc("get available API versions")
+	ws.Route(ws.GET("/").To(s.restfulHandle).
+		Doc("get available API versions").
+		Operation("getAPIVersions").
+		Produces(mediaTypes...).
+		Consumes(mediaTypes...).
+		Writes(metav1.APIGroupList{}))
+	return ws
+}