Kubelet creates and manages node leases

This extends the Kubelet to create and periodically update leases in a
new kube-node-lease namespace. Based on [KEP-0009](https://github.com/kubernetes/community/blob/master/keps/sig-node/0009-node-heartbeat.md),
these leases can be used as a node health signal, and will allow us to
reduce the load caused by over-frequent node status reporting.

- add NodeLease feature gate
- add kube-node-lease system namespace for node leases
- add Kubelet option for lease duration
- add Kubelet-internal lease controller to create and update lease
- add e2e test for NodeLease feature
- modify node authorizer and node restriction admission controller
to allow Kubelets access to corresponding leases

pkg/master/controller.go

@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/golang/glog"
+	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/intstr"
@@ -29,8 +30,10 @@ import (
 	"k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/apimachinery/pkg/util/wait"
 	genericapiserver "k8s.io/apiserver/pkg/server"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	api "k8s.io/kubernetes/pkg/apis/core"
 	coreclient "k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset/typed/core/internalversion"
+	"k8s.io/kubernetes/pkg/features"
 	"k8s.io/kubernetes/pkg/master/reconcilers"
 	"k8s.io/kubernetes/pkg/registry/core/rangeallocation"
 	corerest "k8s.io/kubernetes/pkg/registry/core/rest"
@@ -84,6 +87,11 @@ func (c *completedConfig) NewBootstrapController(legacyRESTStorage corerest.Lega
 		glog.Fatalf("failed to get listener address: %v", err)
 	}
 
+	systemNamespaces := []string{metav1.NamespaceSystem, metav1.NamespacePublic}
+	if utilfeature.DefaultFeatureGate.Enabled(features.NodeLease) {
+		systemNamespaces = append(systemNamespaces, corev1.NamespaceNodeLease)
+	}
+
 	return &Controller{
 		ServiceClient:   serviceClient,
 		NamespaceClient: nsClient,
@@ -92,7 +100,7 @@ func (c *completedConfig) NewBootstrapController(legacyRESTStorage corerest.Lega
 		EndpointReconciler: c.ExtraConfig.EndpointReconcilerConfig.Reconciler,
 		EndpointInterval:   c.ExtraConfig.EndpointReconcilerConfig.Interval,
 
-		SystemNamespaces:         []string{metav1.NamespaceSystem, metav1.NamespacePublic},
+		SystemNamespaces:         systemNamespaces,
 		SystemNamespacesInterval: 1 * time.Minute,
 
 		ServiceClusterIPRegistry: legacyRESTStorage.ServiceClusterIPAllocator,