replicasetcontroller.go

/*
Copyright 2016 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 replicaset

import (
	"bytes"
	"encoding/json"
	"fmt"
	"sort"
	"time"

	"github.com/golang/glog"

	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/apimachinery/pkg/watch"
	clientv1 "k8s.io/client-go/pkg/api/v1"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/tools/record"
	"k8s.io/client-go/util/flowcontrol"
	"k8s.io/client-go/util/workqueue"
	fed "k8s.io/kubernetes/federation/apis/federation"
	fedv1 "k8s.io/kubernetes/federation/apis/federation/v1beta1"
	fedclientset "k8s.io/kubernetes/federation/client/clientset_generated/federation_clientset"
	fedutil "k8s.io/kubernetes/federation/pkg/federation-controller/util"
	"k8s.io/kubernetes/federation/pkg/federation-controller/util/deletionhelper"
	"k8s.io/kubernetes/federation/pkg/federation-controller/util/eventsink"
	"k8s.io/kubernetes/federation/pkg/federation-controller/util/planner"
	"k8s.io/kubernetes/federation/pkg/federation-controller/util/podanalyzer"
	"k8s.io/kubernetes/pkg/api"
	apiv1 "k8s.io/kubernetes/pkg/api/v1"
	extensionsv1 "k8s.io/kubernetes/pkg/apis/extensions/v1beta1"
	kubeclientset "k8s.io/kubernetes/pkg/client/clientset_generated/clientset"
	extensionslisters "k8s.io/kubernetes/pkg/client/listers/extensions/v1beta1"
	"k8s.io/kubernetes/pkg/controller"
)

const (
	FedReplicaSetPreferencesAnnotation = "federation.kubernetes.io/replica-set-preferences"
	allClustersKey                     = "THE_ALL_CLUSTER_KEY"
	UserAgentName                      = "federation-replicaset-controller"
	ControllerName                     = "replicasets"
)

var (
	RequiredResources        = []schema.GroupVersionResource{extensionsv1.SchemeGroupVersion.WithResource("replicasets")}
	replicaSetReviewDelay    = 10 * time.Second
	clusterAvailableDelay    = 20 * time.Second
	clusterUnavailableDelay  = 60 * time.Second
	allReplicaSetReviewDelay = 2 * time.Minute
	updateTimeout            = 30 * time.Second
)

func parseFederationReplicaSetReference(frs *extensionsv1.ReplicaSet) (*fed.FederatedReplicaSetPreferences, error) {
	if frs.Annotations == nil {
		return nil, nil
	}
	frsPrefString, found := frs.Annotations[FedReplicaSetPreferencesAnnotation]
	if !found {
		return nil, nil
	}
	var frsPref fed.FederatedReplicaSetPreferences
	if err := json.Unmarshal([]byte(frsPrefString), &frsPref); err != nil {
		return nil, err
	}
	return &frsPref, nil
}

type ReplicaSetController struct {
	fedClient fedclientset.Interface

	replicaSetController cache.Controller
	replicaSetLister     extensionslisters.ReplicaSetLister

	fedReplicaSetInformer fedutil.FederatedInformer
	fedPodInformer        fedutil.FederatedInformer

	replicasetDeliverer *fedutil.DelayingDeliverer
	clusterDeliverer    *fedutil.DelayingDeliverer
	replicasetWorkQueue workqueue.Interface
	// For updating members of federation.
	fedUpdater fedutil.FederatedUpdater

	replicaSetBackoff *flowcontrol.Backoff
	// For events
	eventRecorder record.EventRecorder

	deletionHelper *deletionhelper.DeletionHelper

	defaultPlanner *planner.Planner
}

// NewReplicaSetController returns a new replicaset controller
func NewReplicaSetController(federationClient fedclientset.Interface) *ReplicaSetController {
	broadcaster := record.NewBroadcaster()
	broadcaster.StartRecordingToSink(eventsink.NewFederatedEventSink(federationClient))
	recorder := broadcaster.NewRecorder(api.Scheme, clientv1.EventSource{Component: UserAgentName})

	frsc := &ReplicaSetController{
		fedClient:           federationClient,
		replicasetDeliverer: fedutil.NewDelayingDeliverer(),
		clusterDeliverer:    fedutil.NewDelayingDeliverer(),
		replicasetWorkQueue: workqueue.New(),
		replicaSetBackoff:   flowcontrol.NewBackOff(5*time.Second, time.Minute),
		defaultPlanner: planner.NewPlanner(&fed.FederatedReplicaSetPreferences{
			Clusters: map[string]fed.ClusterReplicaSetPreferences{
				"*": {Weight: 1},
			},
		}),
		eventRecorder: recorder,
	}

	replicaSetFedInformerFactory := func(cluster *fedv1.Cluster, clientset kubeclientset.Interface) (cache.Store, cache.Controller) {
		return cache.NewInformer(
			&cache.ListWatch{
				ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
					return clientset.Extensions().ReplicaSets(metav1.NamespaceAll).List(options)
				},
				WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
					return clientset.Extensions().ReplicaSets(metav1.NamespaceAll).Watch(options)
				},
			},
			&extensionsv1.ReplicaSet{},
			controller.NoResyncPeriodFunc(),
			fedutil.NewTriggerOnAllChanges(
				func(obj runtime.Object) { frsc.deliverLocalReplicaSet(obj, replicaSetReviewDelay) },
			),
		)
	}
	clusterLifecycle := fedutil.ClusterLifecycleHandlerFuncs{
		ClusterAvailable: func(cluster *fedv1.Cluster) {
			frsc.clusterDeliverer.DeliverAfter(allClustersKey, nil, clusterAvailableDelay)
		},
		ClusterUnavailable: func(cluster *fedv1.Cluster, _ []interface{}) {
			frsc.clusterDeliverer.DeliverAfter(allClustersKey, nil, clusterUnavailableDelay)
		},
	}
	frsc.fedReplicaSetInformer = fedutil.NewFederatedInformer(federationClient, replicaSetFedInformerFactory, &clusterLifecycle)

	podFedInformerFactory := func(cluster *fedv1.Cluster, clientset kubeclientset.Interface) (cache.Store, cache.Controller) {
		return cache.NewInformer(
			&cache.ListWatch{
				ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
					return clientset.Core().Pods(metav1.NamespaceAll).List(options)
				},
				WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
					return clientset.Core().Pods(metav1.NamespaceAll).Watch(options)
				},
			},
			&apiv1.Pod{},
			controller.NoResyncPeriodFunc(),
			fedutil.NewTriggerOnAllChanges(
				func(obj runtime.Object) {
					frsc.clusterDeliverer.DeliverAfter(allClustersKey, nil, allReplicaSetReviewDelay)
				},
			),
		)
	}
	frsc.fedPodInformer = fedutil.NewFederatedInformer(federationClient, podFedInformerFactory, &fedutil.ClusterLifecycleHandlerFuncs{})

	var replicaSetIndexer cache.Indexer
	replicaSetIndexer, frsc.replicaSetController = cache.NewIndexerInformer(
		&cache.ListWatch{
			ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
				return frsc.fedClient.Extensions().ReplicaSets(metav1.NamespaceAll).List(options)
			},
			WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
				return frsc.fedClient.Extensions().ReplicaSets(metav1.NamespaceAll).Watch(options)
			},
		},
		&extensionsv1.ReplicaSet{},
		controller.NoResyncPeriodFunc(),
		fedutil.NewTriggerOnMetaAndSpecChanges(
			func(obj runtime.Object) { frsc.deliverFedReplicaSetObj(obj, replicaSetReviewDelay) },
		),
		cache.Indexers{cache.NamespaceIndex: cache.MetaNamespaceIndexFunc},
	)
	frsc.replicaSetLister = extensionslisters.NewReplicaSetLister(replicaSetIndexer)

	frsc.fedUpdater = fedutil.NewFederatedUpdater(frsc.fedReplicaSetInformer, "replicaset", frsc.eventRecorder,
		func(client kubeclientset.Interface, obj runtime.Object) error {
			rs := obj.(*extensionsv1.ReplicaSet)
			_, err := client.Extensions().ReplicaSets(rs.Namespace).Create(rs)
			return err
		},
		func(client kubeclientset.Interface, obj runtime.Object) error {
			rs := obj.(*extensionsv1.ReplicaSet)
			_, err := client.Extensions().ReplicaSets(rs.Namespace).Update(rs)
			return err
		},
		func(client kubeclientset.Interface, obj runtime.Object) error {
			rs := obj.(*extensionsv1.ReplicaSet)
			orphanDependents := false
			err := client.Extensions().ReplicaSets(rs.Namespace).Delete(rs.Name, &metav1.DeleteOptions{OrphanDependents: &orphanDependents})
			return err
		})

	frsc.deletionHelper = deletionhelper.NewDeletionHelper(
		frsc.updateReplicaSet,
		// objNameFunc
		func(obj runtime.Object) string {
			replicaset := obj.(*extensionsv1.ReplicaSet)
			return fmt.Sprintf("%s/%s", replicaset.Namespace, replicaset.Name)
		},
		updateTimeout,
		frsc.fedReplicaSetInformer,
		frsc.fedUpdater,
	)

	return frsc
}

// Sends the given updated object to apiserver.
// Assumes that the given object is a replicaset.
func (frsc *ReplicaSetController) updateReplicaSet(obj runtime.Object) (runtime.Object, error) {
	replicaset := obj.(*extensionsv1.ReplicaSet)
	return frsc.fedClient.Extensions().ReplicaSets(replicaset.Namespace).Update(replicaset)
}

func (frsc *ReplicaSetController) Run(workers int, stopCh <-chan struct{}) {
	go frsc.replicaSetController.Run(stopCh)
	frsc.fedReplicaSetInformer.Start()
	frsc.fedPodInformer.Start()

	frsc.replicasetDeliverer.StartWithHandler(func(item *fedutil.DelayingDelivererItem) {
		frsc.replicasetWorkQueue.Add(item.Key)
	})
	frsc.clusterDeliverer.StartWithHandler(func(_ *fedutil.DelayingDelivererItem) {
		frsc.reconcileReplicaSetsOnClusterChange()
	})

	for !frsc.isSynced() {
		time.Sleep(5 * time.Millisecond)
	}

	for i := 0; i < workers; i++ {
		go wait.Until(frsc.worker, time.Second, stopCh)
	}

	fedutil.StartBackoffGC(frsc.replicaSetBackoff, stopCh)

	<-stopCh
	glog.Infof("Shutting down ReplicaSetController")
	frsc.replicasetDeliverer.Stop()
	frsc.clusterDeliverer.Stop()
	frsc.replicasetWorkQueue.ShutDown()
	frsc.fedReplicaSetInformer.Stop()
	frsc.fedPodInformer.Stop()
}

func (frsc *ReplicaSetController) isSynced() bool {
	if !frsc.fedReplicaSetInformer.ClustersSynced() {
		glog.V(2).Infof("Cluster list not synced")
		return false
	}
	clusters, err := frsc.fedReplicaSetInformer.GetReadyClusters()
	if err != nil {
		glog.Errorf("Failed to get ready clusters: %v", err)
		return false
	}
	if !frsc.fedReplicaSetInformer.GetTargetStore().ClustersSynced(clusters) {
		return false
	}

	if !frsc.fedPodInformer.ClustersSynced() {
		glog.V(2).Infof("Cluster list not synced")
		return false
	}
	clusters2, err := frsc.fedPodInformer.GetReadyClusters()
	if err != nil {
		glog.Errorf("Failed to get ready clusters: %v", err)
		return false
	}

	// This also checks whether podInformer and replicaSetInformer have the
	// same cluster lists.
	if !frsc.fedPodInformer.GetTargetStore().ClustersSynced(clusters) {
		return false
	}
	if !frsc.fedPodInformer.GetTargetStore().ClustersSynced(clusters2) {
		return false
	}

	if !frsc.replicaSetController.HasSynced() {
		glog.V(2).Infof("federation replicaset list not synced")
		return false
	}
	return true
}

func (frsc *ReplicaSetController) deliverLocalReplicaSet(obj interface{}, duration time.Duration) {
	key, err := controller.KeyFunc(obj)
	if err != nil {
		glog.Errorf("Couldn't get key for object %v: %v", obj, err)
		return
	}
	namespace, name, err := cache.SplitMetaNamespaceKey(key)
	if err != nil {
		glog.Errorf("Error splitting key for object %v: %v", obj, err)
	}
	_, err = frsc.replicaSetLister.ReplicaSets(namespace).Get(name)
	switch {
	case errors.IsNotFound(err):
		// do nothing
	case err != nil:
		glog.Errorf("Couldn't get federation replicaset %v: %v", key, err)
	default:
		// ReplicaSet exists. Ignore ReplicaSets that exist only in local k8s
		frsc.deliverReplicaSetByKey(key, duration, false)
	}
}

func (frsc *ReplicaSetController) deliverFedReplicaSetObj(obj interface{}, delay time.Duration) {
	key, err := controller.KeyFunc(obj)
	if err != nil {
		glog.Errorf("Couldn't get key for object %+v: %v", obj, err)
		return
	}
	frsc.deliverReplicaSetByKey(key, delay, false)
}

func (frsc *ReplicaSetController) deliverReplicaSetByKey(key string, delay time.Duration, failed bool) {
	if failed {
		frsc.replicaSetBackoff.Next(key, time.Now())
		delay = delay + frsc.replicaSetBackoff.Get(key)
	} else {
		frsc.replicaSetBackoff.Reset(key)
	}
	frsc.replicasetDeliverer.DeliverAfter(key, nil, delay)
}

func (frsc *ReplicaSetController) worker() {
	for {
		item, quit := frsc.replicasetWorkQueue.Get()
		if quit {
			return
		}
		key := item.(string)
		status, err := frsc.reconcileReplicaSet(key)
		frsc.replicasetWorkQueue.Done(item)
		if err != nil {
			glog.Errorf("Error syncing cluster controller: %v", err)
			frsc.deliverReplicaSetByKey(key, 0, true)
		} else {
			switch status {
			case statusAllOk:
				break
			case statusError:
				frsc.deliverReplicaSetByKey(key, 0, true)
			case statusNeedRecheck:
				frsc.deliverReplicaSetByKey(key, replicaSetReviewDelay, false)
			case statusNotSynced:
				frsc.deliverReplicaSetByKey(key, clusterAvailableDelay, false)
			default:
				glog.Errorf("Unhandled reconciliation status: %s", status)
				frsc.deliverReplicaSetByKey(key, replicaSetReviewDelay, false)
			}
		}
	}
}

func (frsc *ReplicaSetController) schedule(frs *extensionsv1.ReplicaSet, clusters []*fedv1.Cluster,
	current map[string]int64, estimatedCapacity map[string]int64) map[string]int64 {
	// TODO: integrate real scheduler

	plnr := frsc.defaultPlanner
	frsPref, err := parseFederationReplicaSetReference(frs)
	if err != nil {
		glog.Info("Invalid ReplicaSet specific preference, use default. rs: %v, err: %v", frs, err)
	}
	if frsPref != nil { // create a new planner if user specified a preference
		plnr = planner.NewPlanner(frsPref)
	}

	replicas := int64(*frs.Spec.Replicas)
	var clusterNames []string
	for _, cluster := range clusters {
		clusterNames = append(clusterNames, cluster.Name)
	}
	scheduleResult, overflow := plnr.Plan(replicas, clusterNames, current, estimatedCapacity,
		frs.Namespace+"/"+frs.Name)
	// make sure the return contains clusters need to zero the replicas
	result := make(map[string]int64)
	for clusterName := range current {
		result[clusterName] = 0
	}
	for clusterName, replicas := range scheduleResult {
		result[clusterName] = replicas
	}
	for clusterName, replicas := range overflow {
		result[clusterName] += replicas
	}
	if glog.V(4) {
		buf := bytes.NewBufferString(fmt.Sprintf("Schedule - ReplicaSet: %s/%s\n", frs.Namespace, frs.Name))
		sort.Strings(clusterNames)
		for _, clusterName := range clusterNames {
			cur := current[clusterName]
			target := scheduleResult[clusterName]
			fmt.Fprintf(buf, "%s: current: %d target: %d", clusterName, cur, target)
			if over, found := overflow[clusterName]; found {
				fmt.Fprintf(buf, " overflow: %d", over)
			}
			if capacity, found := estimatedCapacity[clusterName]; found {
				fmt.Fprintf(buf, " capacity: %d", capacity)
			}
			fmt.Fprintf(buf, "\n")
		}
		glog.V(4).Infof(buf.String())
	}
	return result
}

type reconciliationStatus string

const (
	statusAllOk       = reconciliationStatus("ALL_OK")
	statusNeedRecheck = reconciliationStatus("RECHECK")
	statusError       = reconciliationStatus("ERROR")
	statusNotSynced   = reconciliationStatus("NOSYNC")
)

func (frsc *ReplicaSetController) reconcileReplicaSet(key string) (reconciliationStatus, error) {
	if !frsc.isSynced() {
		return statusNotSynced, nil
	}

	glog.V(4).Infof("Start reconcile replicaset %q", key)
	startTime := time.Now()
	defer glog.V(4).Infof("Finished reconcile replicaset %q (%v)", key, time.Now().Sub(startTime))

	namespace, name, err := cache.SplitMetaNamespaceKey(key)
	if err != nil {
		return statusError, err
	}
	objFromStore, err := frsc.replicaSetLister.ReplicaSets(namespace).Get(name)
	if errors.IsNotFound(err) {
		// don't delete local replicasets for now. Do not reconcile it anymore.
		return statusAllOk, nil
	}
	if err != nil {
		return statusError, err
	}
	obj, err := api.Scheme.DeepCopy(objFromStore)
	frs, ok := obj.(*extensionsv1.ReplicaSet)
	if err != nil || !ok {
		glog.Errorf("Error in retrieving obj from store: %v, %v", ok, err)
		frsc.deliverReplicaSetByKey(key, 0, true)
		return statusError, err
	}
	if frs.DeletionTimestamp != nil {
		if err := frsc.delete(frs); err != nil {
			glog.Errorf("Failed to delete %s: %v", frs, err)
			frsc.eventRecorder.Eventf(frs, api.EventTypeWarning, "DeleteFailed",
				"ReplicaSet delete failed: %v", err)
			frsc.deliverReplicaSetByKey(key, 0, true)
			return statusError, err
		}
		return statusAllOk, nil
	}

	glog.V(3).Infof("Ensuring delete object from underlying clusters finalizer for replicaset: %s",
		frs.Name)
	// Add the required finalizers before creating a replicaset in underlying clusters.
	updatedRsObj, err := frsc.deletionHelper.EnsureFinalizers(frs)
	if err != nil {
		glog.Errorf("Failed to ensure delete object from underlying clusters finalizer in replicaset %s: %v",
			frs.Name, err)
		frsc.deliverReplicaSetByKey(key, 0, false)
		return statusError, err
	}
	frs = updatedRsObj.(*extensionsv1.ReplicaSet)

	glog.V(3).Infof("Syncing replicaset %s in underlying clusters", frs.Name)

	clusters, err := frsc.fedReplicaSetInformer.GetReadyClusters()
	if err != nil {
		return statusError, err
	}

	// collect current status and do schedule
	allPods, err := frsc.fedPodInformer.GetTargetStore().List()
	if err != nil {
		return statusError, err
	}
	podStatus, err := podanalyzer.AnalysePods(frs.Spec.Selector, allPods, time.Now())
	current := make(map[string]int64)
	estimatedCapacity := make(map[string]int64)
	for _, cluster := range clusters {
		lrsObj, exists, err := frsc.fedReplicaSetInformer.GetTargetStore().GetByKey(cluster.Name, key)
		if err != nil {
			return statusError, err
		}
		if exists {
			lrs := lrsObj.(*extensionsv1.ReplicaSet)
			current[cluster.Name] = int64(podStatus[cluster.Name].RunningAndReady) // include pending as well?
			unschedulable := int64(podStatus[cluster.Name].Unschedulable)
			if unschedulable > 0 {
				estimatedCapacity[cluster.Name] = int64(*lrs.Spec.Replicas) - unschedulable
			}
		}
	}

	scheduleResult := frsc.schedule(frs, clusters, current, estimatedCapacity)

	glog.V(4).Infof("Start syncing local replicaset %s: %v", key, scheduleResult)

	fedStatus := extensionsv1.ReplicaSetStatus{ObservedGeneration: frs.Generation}
	operations := make([]fedutil.FederatedOperation, 0)
	for clusterName, replicas := range scheduleResult {

		lrsObj, exists, err := frsc.fedReplicaSetInformer.GetTargetStore().GetByKey(clusterName, key)
		if err != nil {
			return statusError, err
		}

		// The object can be modified.
		lrs := &extensionsv1.ReplicaSet{
			ObjectMeta: fedutil.DeepCopyRelevantObjectMeta(frs.ObjectMeta),
			Spec:       *fedutil.DeepCopyApiTypeOrPanic(&frs.Spec).(*extensionsv1.ReplicaSetSpec),
		}
		specReplicas := int32(replicas)
		lrs.Spec.Replicas = &specReplicas

		if !exists {
			if replicas > 0 {
				operations = append(operations, fedutil.FederatedOperation{
					Type:        fedutil.OperationTypeAdd,
					Obj:         lrs,
					ClusterName: clusterName,
					Key:         key,
				})
			}
		} else {
			currentLrs := lrsObj.(*extensionsv1.ReplicaSet)
			// Update existing replica set, if needed.
			if !fedutil.ObjectMetaAndSpecEquivalent(lrs, currentLrs) {
				operations = append(operations, fedutil.FederatedOperation{
					Type:        fedutil.OperationTypeUpdate,
					Obj:         lrs,
					ClusterName: clusterName,
					Key:         key,
				})
			}
			fedStatus.Replicas += currentLrs.Status.Replicas
			fedStatus.FullyLabeledReplicas += currentLrs.Status.FullyLabeledReplicas
			fedStatus.ReadyReplicas += currentLrs.Status.ReadyReplicas
			fedStatus.AvailableReplicas += currentLrs.Status.AvailableReplicas
		}
	}
	if fedStatus.Replicas != frs.Status.Replicas || fedStatus.FullyLabeledReplicas != frs.Status.FullyLabeledReplicas ||
		fedStatus.ReadyReplicas != frs.Status.ReadyReplicas || fedStatus.AvailableReplicas != frs.Status.AvailableReplicas {
		frs.Status = fedStatus
		_, err = frsc.fedClient.Extensions().ReplicaSets(frs.Namespace).UpdateStatus(frs)
		if err != nil {
			return statusError, err
		}
	}

	if len(operations) == 0 {
		// Everything is in order
		return statusAllOk, nil
	}
	err = frsc.fedUpdater.Update(operations, updateTimeout)
	if err != nil {
		glog.Errorf("Failed to execute updates for %s: %v", key, err)
		return statusError, err
	}

	// Some operations were made, reconcile after a while.
	return statusNeedRecheck, nil
}

func (frsc *ReplicaSetController) reconcileReplicaSetsOnClusterChange() {
	if !frsc.isSynced() {
		frsc.clusterDeliverer.DeliverAfter(allClustersKey, nil, clusterAvailableDelay)
	}
	rss, err := frsc.replicaSetLister.List(labels.Everything())
	if err != nil {
		utilruntime.HandleError(fmt.Errorf("error listing replica sets: %v", err))
		return
	}
	for _, rs := range rss {
		key, _ := controller.KeyFunc(rs)
		frsc.deliverReplicaSetByKey(key, 0, false)
	}
}

// delete deletes the given replicaset or returns error if the deletion was not complete.
func (frsc *ReplicaSetController) delete(replicaset *extensionsv1.ReplicaSet) error {
	glog.V(3).Infof("Handling deletion of replicaset: %v", *replicaset)
	_, err := frsc.deletionHelper.HandleObjectInUnderlyingClusters(replicaset)
	if err != nil {
		return err
	}

	err = frsc.fedClient.Extensions().ReplicaSets(replicaset.Namespace).Delete(replicaset.Name, nil)
	if err != nil {
		// Its all good if the error is not found error. That means it is deleted already and we do not have to do anything.
		// This is expected when we are processing an update as a result of replicaset finalizer deletion.
		// The process that deleted the last finalizer is also going to delete the replicaset and we do not have to do anything.
		if !errors.IsNotFound(err) {
			return fmt.Errorf("failed to delete replicaset: %v", err)
		}
	}
	return nil
}