Add node provider interfaace (#526)

This starts the work of having a `NodeProvider` which is responsible for
providing node details.
It splits the responsibilities of node management off to a new
controller.

The primary change here is to add the framework pieces for node
management and move the VK CLI to use this new controller.

It also adds support for node leases where available. This can be
enabled via the command line (disabled by default), but may fall back if
we find that leaess aren't supported on the cluster.

vkubelet/vkubelet.go

@@ -5,7 +5,6 @@ import (
 	"time"
 
 	"go.opencensus.io/trace"
-	corev1 "k8s.io/api/core/v1"
 	corev1informers "k8s.io/client-go/informers/core/v1"
 	"k8s.io/client-go/kubernetes"
 
@@ -19,10 +18,9 @@ const (
 
 // Server masquarades itself as a kubelet and allows for the virtual node to be backed by non-vm/node providers.
 type Server struct {
-	nodeName        string
 	namespace       string
+	nodeName        string
 	k8sClient       *kubernetes.Clientset
-	taint           *corev1.Taint
 	provider        providers.Provider
 	resourceManager *manager.ResourceManager
 	podSyncWorkers  int
@@ -36,7 +34,6 @@ type Config struct {
 	NodeName        string
 	Provider        providers.Provider
 	ResourceManager *manager.ResourceManager
-	Taint           *corev1.Taint
 	PodSyncWorkers  int
 	PodInformer     corev1informers.PodInformer
 }
@@ -48,9 +45,8 @@ type Config struct {
 // You must call `Run` on the returned object to start the server.
 func New(cfg Config) *Server {
 	return &Server{
-		namespace:       cfg.Namespace,
 		nodeName:        cfg.NodeName,
-		taint:           cfg.Taint,
+		namespace:       cfg.Namespace,
 		k8sClient:       cfg.Client,
 		resourceManager: cfg.ResourceManager,
 		provider:        cfg.Provider,
@@ -65,10 +61,6 @@ func New(cfg Config) *Server {
 // info to the Kubernetes API Server, such as logs, metrics, exec, etc.
 // See `AttachPodRoutes` and `AttachMetricsRoutes` to set these up.
 func (s *Server) Run(ctx context.Context) error {
-	if err := s.registerNode(ctx); err != nil {
-		return err
-	}
-
 	go s.providerSyncLoop(ctx)
 
 	return NewPodController(s).Run(ctx, s.podSyncWorkers)
@@ -89,7 +81,6 @@ func (s *Server) providerSyncLoop(ctx context.Context) {
 			t.Stop()
 
 			ctx, span := trace.StartSpan(ctx, "syncActualState")
-			s.updateNode(ctx)
 			s.updatePodStatuses(ctx)
 			span.End()