add functional Option type to Kubelet, add SetNodeStatus Option, migrate node statue update funcs to slice of callbacks

cmd/kubelet/app/server.go

@@ -753,6 +753,7 @@ type KubeletConfig struct {
 	NodeIP                     net.IP
 	ContainerRuntimeOptions    []kubecontainer.Option
 	HairpinMode                string
+	Options                    []kubelet.Option
 }
 
 func CreateAndInitKubelet(kc *KubeletConfig) (k KubeletBootstrap, pc *config.PodConfig, err error) {
@@ -839,6 +840,7 @@ func CreateAndInitKubelet(kc *KubeletConfig) (k KubeletBootstrap, pc *config.Pod
 		kc.VolumeStatsAggPeriod,
 		kc.ContainerRuntimeOptions,
 		kc.HairpinMode,
+		kc.Options,
 	)
 
 	if err != nil {

pkg/kubelet/kubelet.go

@@ -146,6 +146,9 @@ type SyncHandler interface {
 
 type SourcesReadyFn func(sourcesSeen sets.String) bool
 
+// Option is a functional option type for Kubelet
+type Option func(*Kubelet)
+
 // New instantiates a new Kubelet object along with all the required internal modules.
 // No initialization of Kubelet and its modules should happen here.
 func NewMainKubelet(
@@ -206,6 +209,7 @@ func NewMainKubelet(
 	volumeStatsAggPeriod time.Duration,
 	containerRuntimeOptions []kubecontainer.Option,
 	hairpinMode string,
+	kubeOptions []Option,
 ) (*Kubelet, error) {
 	if rootDirectory == "" {
 		return nil, fmt.Errorf("invalid root directory %q", rootDirectory)
@@ -458,6 +462,12 @@ func NewMainKubelet(
 	klet.backOff = util.NewBackOff(backOffPeriod, MaxContainerBackOff)
 	klet.podKillingCh = make(chan *kubecontainer.PodPair, podKillingChannelCapacity)
 	klet.sourcesSeen = sets.NewString()
+	klet.setNodeStatusFuncs = klet.defaultNodeStatusFuncs()
+
+	// apply functional Option's
+	for _, opt := range kubeOptions {
+		opt(klet)
+	}
 	return klet, nil
 }
 
@@ -690,6 +700,9 @@ type Kubelet struct {
 	// (make cbr0 promiscuous), "hairpin-veth" (set the hairpin flag on veth interfaces)
 	// or "none" (do nothing).
 	hairpinMode componentconfig.HairpinMode
+
+	// handlers called during the tryUpdateNodeStatus cycle
+	setNodeStatusFuncs []func(*api.Node) error
 }
 
 // Validate given node IP belongs to the current host
@@ -3002,16 +3015,39 @@ func (kl *Kubelet) recordNodeSchdulableEvent(node *api.Node) {
 // TODO(madhusudancs): Simplify the logic for setting node conditions and
 // refactor the node status condtion code out to a different file.
 func (kl *Kubelet) setNodeStatus(node *api.Node) error {
-	if err := kl.setNodeAddress(node); err != nil {
+	for _, f := range kl.setNodeStatusFuncs {
+		if err := f(node); err != nil {
 			return err
 		}
-	kl.setNodeStatusInfo(node)
+	}
-	kl.setNodeOODCondition(node)
-	kl.setNodeReadyCondition(node)
-	kl.recordNodeSchdulableEvent(node)
 	return nil
 }
 
+// defaultNodeStatusFuncs is a factory that generates the default set of setNodeStatus funcs
+func (kl *Kubelet) defaultNodeStatusFuncs() []func(*api.Node) error {
+	// initial set of node status update handlers, can be modified by Option's
+	withoutError := func(f func(*api.Node)) func(*api.Node) error {
+		return func(n *api.Node) error {
+			f(n)
+			return nil
+		}
+	}
+	return []func(*api.Node) error{
+		kl.setNodeAddress,
+		withoutError(kl.setNodeStatusInfo),
+		withoutError(kl.setNodeOODCondition),
+		withoutError(kl.setNodeReadyCondition),
+		withoutError(kl.recordNodeSchdulableEvent),
+	}
+}
+
+// SetNodeStatus returns a functional Option that adds the given node status update handler to the Kubelet
+func SetNodeStatus(f func(*api.Node) error) Option {
+	return func(k *Kubelet) {
+		k.setNodeStatusFuncs = append(k.setNodeStatusFuncs, f)
+	}
+}
+
 // FIXME: Why not combine this with container runtime health check?
 func (kl *Kubelet) isContainerRuntimeVersionCompatible() error {
 	switch kl.GetRuntime().Type() {

pkg/kubelet/kubelet_test.go

@@ -191,6 +191,7 @@ func newTestKubelet(t *testing.T) *TestKubelet {
 	// Relist period does not affect the tests.
 	kubelet.pleg = pleg.NewGenericPLEG(fakeRuntime, 100, time.Hour, nil)
 	kubelet.clock = fakeClock
+	kubelet.setNodeStatusFuncs = kubelet.defaultNodeStatusFuncs()
 	return &TestKubelet{kubelet, fakeRuntime, mockCadvisor, fakeKubeClient, fakeMirrorClient, fakeClock}
 }