replicaset controller分析

replicaset controller簡介

replicaset controller是kube-controller-manager組件中眾多控制器中的一個，是 replicaset 資源對象的控制器，其通過對replicaset、pod 2種資源的監聽，當這2種資源發生變化時會觸發 replicaset controller 對相應的replicaset對象進行調諧操作，從而完成replicaset期望副本數的調諧，當實際pod的數量未達到預期時創建pod，當實際pod的數量超過預期時刪除pod。

replicaset controller主要作用是根據replicaset對象所期望的pod數量與現存pod數量做比較，然后根據比較結果創建/刪除pod，最終使得replicaset對象所期望的pod數量與現存pod數量相等。

replicaset controller架構圖

replicaset controller的大致組成和處理流程如下圖，replicaset controller對pod和replicaset對象注冊了event handler，當有事件時，會watch到然后將對應的replicaset對象放入到queue中，然后syncReplicaSet方法為replicaset controller調諧replicaset對象的核心處理邏輯所在，從queue中取出replicaset對象，做調諧處理。

replicaset controller分析分為3大塊進行，分別是：
（1）replicaset controller初始化和啟動分析；
（2）replicaset controller核心處理邏輯分析；
（3）replicaset controller expectations機制分析。

本篇博客進行replicaset controller核心處理邏輯分析。

replicaset controller核心處理邏輯分析

基于v1.17.4

經過前面分析的replicaset controller的初始化與啟動，知道了replicaset controller監聽replicaset、pod對象的add、update與delete事件，然后對replicaset對象做相應的調諧處理，這里來接著分析replicaset controller的調諧處理（核心處理）邏輯，從rsc.syncHandler作為入口進行分析。

rsc.syncHandler

rsc.syncHandler即rsc.syncReplicaSet方法，主要邏輯：
（1）獲取replicaset對象以及關聯的pod對象列表；
（2）調用rsc.expectations.SatisfiedExpectations，判斷上一輪對replicaset期望副本的創刪操作是否完成，也可以認為是判斷上一次對replicaset對象的調諧操作中，調用的rsc.manageReplicas方法是否執行完成；
（3）如果上一輪對replicaset期望副本的創刪操作已經完成，且replicaset對象的DeletionTimestamp字段為nil，則調用rsc.manageReplicas做replicaset期望副本的核心調諧處理，即創刪pod；
（4）調用calculateStatus計算replicaset的status，并更新。

// syncReplicaSet will sync the ReplicaSet with the given key if it has had its expectations fulfilled, // meaning it did not expect to see any more of its pods created or deleted. This function is not meant to be // invoked concurrently with the same key. func (rsc *ReplicaSetController) syncReplicaSet(key string) error {startTime := time.Now()defer func() {klog.V(4).Infof("Finished syncing %v %q (%v)", rsc.Kind, key, time.Since(startTime))}()namespace, name, err := cache.SplitMetaNamespaceKey(key)if err != nil {return err}rs, err := rsc.rsLister.ReplicaSets(namespace).Get(name)if errors.IsNotFound(err) {klog.V(4).Infof("%v %v has been deleted", rsc.Kind, key)rsc.expectations.DeleteExpectations(key)return nil}if err != nil {return err}rsNeedsSync := rsc.expectations.SatisfiedExpectations(key)selector, err := metav1.LabelSelectorAsSelector(rs.Spec.Selector)if err != nil {utilruntime.HandleError(fmt.Errorf("error converting pod selector to selector: %v", err))return nil}// list all pods to include the pods that don't match the rs`s selector// anymore but has the stale controller ref.// TODO: Do the List and Filter in a single pass, or use an index.allPods, err := rsc.podLister.Pods(rs.Namespace).List(labels.Everything())if err != nil {return err}// Ignore inactive pods.filteredPods := controller.FilterActivePods(allPods)// NOTE: filteredPods are pointing to objects from cache - if you need to// modify them, you need to copy it first.filteredPods, err = rsc.claimPods(rs, selector, filteredPods)if err != nil {return err}var manageReplicasErr errorif rsNeedsSync && rs.DeletionTimestamp == nil {manageReplicasErr = rsc.manageReplicas(filteredPods, rs)}rs = rs.DeepCopy()newStatus := calculateStatus(rs, filteredPods, manageReplicasErr)// Always updates status as pods come up or die.updatedRS, err := updateReplicaSetStatus(rsc.kubeClient.AppsV1().ReplicaSets(rs.Namespace), rs, newStatus)if err != nil {// Multiple things could lead to this update failing. Requeuing the replica set ensures// Returning an error causes a requeue without forcing a hotloopreturn err}// Resync the ReplicaSet after MinReadySeconds as a last line of defense to guard against clock-skew.if manageReplicasErr == nil && updatedRS.Spec.MinReadySeconds > 0 &&updatedRS.Status.ReadyReplicas == *(updatedRS.Spec.Replicas) &&updatedRS.Status.AvailableReplicas != *(updatedRS.Spec.Replicas) {rsc.queue.AddAfter(key, time.Duration(updatedRS.Spec.MinReadySeconds)*time.Second)}return manageReplicasErr }

1 rsc.expectations.SatisfiedExpectations

該方法主要是判斷上一輪對replicaset期望副本的創刪操作是否完成，也可以認為是判斷上一次對replicaset對象的調諧操作中，調用的rsc.manageReplicas方法是否執行完成。待上一次創建刪除pod的操作完成后，才能進行下一次的rsc.manageReplicas方法調用。

若某replicaset對象的調諧中從未調用過rsc.manageReplicas方法，或上一輪調諧時創建/刪除pod的數量已達成或調用rsc.manageReplicas后已達到超時期限（超時時間5分鐘），則返回true，代表上一次創建刪除pod的操作完成，可以進行下一次的rsc.manageReplicas方法調用，否則返回false。

expectations記錄了replicaset對象在某一次調諧中期望創建/刪除的pod數量，pod創建/刪除完成后，該期望數會相應的減少，當期望創建/刪除的pod數量小于等于0時，說明上一次調諧中期望創建/刪除的pod數量已經達到，返回true。

關于Expectations機制后面會做詳細分析。

// pkg/controller/controller_utils.go func (r *ControllerExpectations) SatisfiedExpectations(controllerKey string) bool {if exp, exists, err := r.GetExpectations(controllerKey); exists {if exp.Fulfilled() {klog.V(4).Infof("Controller expectations fulfilled %#v", exp)return true} else if exp.isExpired() {klog.V(4).Infof("Controller expectations expired %#v", exp)return true} else {klog.V(4).Infof("Controller still waiting on expectations %#v", exp)return false}} else if err != nil {klog.V(2).Infof("Error encountered while checking expectations %#v, forcing sync", err)} else {// When a new controller is created, it doesn't have expectations.// When it doesn't see expected watch events for > TTL, the expectations expire.// - In this case it wakes up, creates/deletes controllees, and sets expectations again.// When it has satisfied expectations and no controllees need to be created/destroyed > TTL, the expectations expire.// - In this case it continues without setting expectations till it needs to create/delete controllees.klog.V(4).Infof("Controller %v either never recorded expectations, or the ttl expired.", controllerKey)}// Trigger a sync if we either encountered and error (which shouldn't happen since we're// getting from local store) or this controller hasn't established expectations.return true }func (exp *ControlleeExpectations) isExpired() bool {return clock.RealClock{}.Since(exp.timestamp) > ExpectationsTimeout // ExpectationsTimeout = 5 * time.Minute }

2 核心創建刪除pod方法-rsc.manageReplicas

核心創建刪除pod方法，主要是根據replicaset所期望的pod數量與現存pod數量做比較，然后根據比較結果來創建/刪除pod，最終使得replicaset對象所期望的pod數量與現存pod數量相等，需要特別注意的是，每一次調用rsc.manageReplicas方法，創建/刪除pod的個數上限為500。

在replicaset對象的調諧中，rsc.manageReplicas方法不一定每一次都會調用執行，只有當rsc.expectations.SatisfiedExpectations方法返回true，且replicaset對象的DeletionTimestamp屬性為空時，才會進行rsc.manageReplicas方法的調用。

先簡單的看一下代碼，代碼后面會做詳細的邏輯分析。

// pkg/controller/replicaset/replica_set.go func (rsc *ReplicaSetController) manageReplicas(filteredPods []*v1.Pod, rs *apps.ReplicaSet) error {diff := len(filteredPods) - int(*(rs.Spec.Replicas))rsKey, err := controller.KeyFunc(rs)if err != nil {utilruntime.HandleError(fmt.Errorf("Couldn't get key for %v %#v: %v", rsc.Kind, rs, err))return nil}if diff < 0 {diff *= -1if diff > rsc.burstReplicas {diff = rsc.burstReplicas}// TODO: Track UIDs of creates just like deletes. The problem currently// is we'd need to wait on the result of a create to record the pod's// UID, which would require locking *across* the create, which will turn// into a performance bottleneck. We should generate a UID for the pod// beforehand and store it via ExpectCreations.rsc.expectations.ExpectCreations(rsKey, diff)glog.V(2).Infof("Too few replicas for %v %s/%s, need %d, creating %d", rsc.Kind, rs.Namespace, rs.Name, *(rs.Spec.Replicas), diff)// Batch the pod creates. Batch sizes start at SlowStartInitialBatchSize// and double with each successful iteration in a kind of "slow start".// This handles attempts to start large numbers of pods that would// likely all fail with the same error. For example a project with a// low quota that attempts to create a large number of pods will be// prevented from spamming the API service with the pod create requests// after one of its pods fails. Conveniently, this also prevents the// event spam that those failures would generate.successfulCreations, err := slowStartBatch(diff, controller.SlowStartInitialBatchSize, func() error {boolPtr := func(b bool) *bool { return &b }controllerRef := &metav1.OwnerReference{APIVersion: rsc.GroupVersion().String(),Kind: rsc.Kind,Name: rs.Name,UID: rs.UID,BlockOwnerDeletion: boolPtr(true),Controller: boolPtr(true),}err := rsc.podControl.CreatePodsWithControllerRef(rs.Namespace, &rs.Spec.Template, rs, controllerRef)if err != nil && errors.IsTimeout(err) {// Pod is created but its initialization has timed out.// If the initialization is successful eventually, the// controller will observe the creation via the informer.// If the initialization fails, or if the pod keeps// uninitialized for a long time, the informer will not// receive any update, and the controller will create a new// pod when the expectation expires.return nil}return err})// Any skipped pods that we never attempted to start shouldn't be expected.// The skipped pods will be retried later. The next controller resync will// retry the slow start process.if skippedPods := diff - successfulCreations; skippedPods > 0 {glog.V(2).Infof("Slow-start failure. Skipping creation of %d pods, decrementing expectations for %v %v/%v", skippedPods, rsc.Kind, rs.Namespace, rs.Name)for i := 0; i < skippedPods; i++ {// Decrement the expected number of creates because the informer won't observe this podrsc.expectations.CreationObserved(rsKey)}}return err} else if diff > 0 {if diff > rsc.burstReplicas {diff = rsc.burstReplicas}glog.V(2).Infof("Too many replicas for %v %s/%s, need %d, deleting %d", rsc.Kind, rs.Namespace, rs.Name, *(rs.Spec.Replicas), diff)// Choose which Pods to delete, preferring those in earlier phases of startup.podsToDelete := getPodsToDelete(filteredPods, diff)// Snapshot the UIDs (ns/name) of the pods we're expecting to see// deleted, so we know to record their expectations exactly once either// when we see it as an update of the deletion timestamp, or as a delete.// Note that if the labels on a pod/rs change in a way that the pod gets// orphaned, the rs will only wake up after the expectations have// expired even if other pods are deleted.rsc.expectations.ExpectDeletions(rsKey, getPodKeys(podsToDelete))errCh := make(chan error, diff)var wg sync.WaitGroupwg.Add(diff)for _, pod := range podsToDelete {go func(targetPod *v1.Pod) {defer wg.Done()if err := rsc.podControl.DeletePod(rs.Namespace, targetPod.Name, rs); err != nil {// Decrement the expected number of deletes because the informer won't observe this deletionpodKey := controller.PodKey(targetPod)glog.V(2).Infof("Failed to delete %v, decrementing expectations for %v %s/%s", podKey, rsc.Kind, rs.Namespace, rs.Name)rsc.expectations.DeletionObserved(rsKey, podKey)errCh <- err}}(pod)}wg.Wait()select {case err := <-errCh:// all errors have been reported before and they're likely to be the same, so we'll only return the first one we hit.if err != nil {return err}default:}}return nil }

diff = 現存pod數量 - 期望的pod數量

diff := len(filteredPods) - int(*(rs.Spec.Replicas))

（1）當現存pod數量比期望的少時，需要創建pod，進入創建pod的邏輯代碼塊。
（2）當現存pod數量比期望的多時，需要刪除pod，進入刪除pod的邏輯代碼塊。

一次同步操作中批量創建或刪除pod的個數上限為rsc.burstReplicas，即500個。

// pkg/controller/replicaset/replica_set.go const (// Realistic value of the burstReplica field for the replica set manager based off// performance requirements for kubernetes 1.0.BurstReplicas = 500// The number of times we retry updating a ReplicaSet's status.statusUpdateRetries = 1 ) if diff > rsc.burstReplicas {diff = rsc.burstReplicas}

接下來分析一下創建/刪除pod的邏輯代碼塊。

2.1 創建pod邏輯代碼塊

主要邏輯：
（1）運算獲取需要創建的pod數量，并設置數量上限500；
（2）調用rsc.expectations.ExpectCreations，將本輪調諧期望創建的pod數量設置進expectations；
（3）調用slowStartBatch函數來對pod進行創建邏輯處理；
（4）調用slowStartBatch函數完成后，計算獲取創建失敗的pod的數量，然后調用相應次數的rsc.expectations.CreationObserved方法，減去本輪調諧中期望創建的pod數量。
為什么要減呢？因為expectations記錄了replicaset對象在某一次調諧中期望創建/刪除的pod數量，pod創建/刪除完成后，replicaset controller會watch到pod的創建/刪除事件，從而調用rsc.expectations.CreationObserved方法來使期望創建/刪除的pod數量減少。當有相應數量的pod創建/刪除失敗后，replicaset controller是不會watch到相應的pod創建/刪除事件的，所以必須把本輪調諧期望創建/刪除的pod數量做相應的減法，否則本輪調諧中的期望創建/刪除pod數量永遠不可能小于等于0，這樣的話，rsc.expectations.SatisfiedExpectations方法就只會等待expectations超時期限到達才會返回true了。

diff *= -1if diff > rsc.burstReplicas {diff = rsc.burstReplicas}rsc.expectations.ExpectCreations(rsKey, diff)glog.V(2).Infof("Too few replicas for %v %s/%s, need %d, creating %d", rsc.Kind, rs.Namespace, rs.Name, *(rs.Spec.Replicas), diff)successfulCreations, err := slowStartBatch(diff, controller.SlowStartInitialBatchSize, func() error {boolPtr := func(b bool) *bool { return &b }controllerRef := &metav1.OwnerReference{APIVersion: rsc.GroupVersion().String(),Kind: rsc.Kind,Name: rs.Name,UID: rs.UID,BlockOwnerDeletion: boolPtr(true),Controller: boolPtr(true),}err := rsc.podControl.CreatePodsWithControllerRef(rs.Namespace, &rs.Spec.Template, rs, controllerRef)if err != nil && errors.IsTimeout(err) {// Pod is created but its initialization has timed out.// If the initialization is successful eventually, the// controller will observe the creation via the informer.// If the initialization fails, or if the pod keeps// uninitialized for a long time, the informer will not// receive any update, and the controller will create a new// pod when the expectation expires.return nil}return err})if skippedPods := diff - successfulCreations; skippedPods > 0 {glog.V(2).Infof("Slow-start failure. Skipping creation of %d pods, decrementing expectations for %v %v/%v", skippedPods, rsc.Kind, rs.Namespace, rs.Name)for i := 0; i < skippedPods; i++ {// Decrement the expected number of creates because the informer won't observe this podrsc.expectations.CreationObserved(rsKey)}}return err

2.1.1 slowStartBatch

來看到slowStartBatch，可以看到創建pod的算法為：
（1）每次批量創建的 pod 數依次為 1、2、4、8…，呈指數級增長，起與要創建的pod數量相同的goroutine來負責創建pod。
（2）創建pod按1、2、4、8…的遞增趨勢分多批次進行，若某批次創建pod有失敗的（如apiserver限流，丟棄請求等，注意：超時除外，因為initialization處理有可能超時），則后續批次不再進行，結束本次函數調用。

// pkg/controller/replicaset/replica_set.go // slowStartBatch tries to call the provided function a total of 'count' times, // starting slow to check for errors, then speeding up if calls succeed. // // It groups the calls into batches, starting with a group of initialBatchSize. // Within each batch, it may call the function multiple times concurrently. // // If a whole batch succeeds, the next batch may get exponentially larger. // If there are any failures in a batch, all remaining batches are skipped // after waiting for the current batch to complete. // // It returns the number of successful calls to the function. func slowStartBatch(count int, initialBatchSize int, fn func() error) (int, error) {remaining := countsuccesses := 0for batchSize := integer.IntMin(remaining, initialBatchSize); batchSize > 0; batchSize = integer.IntMin(2*batchSize, remaining) {errCh := make(chan error, batchSize)var wg sync.WaitGroupwg.Add(batchSize)for i := 0; i < batchSize; i++ {go func() {defer wg.Done()if err := fn(); err != nil {errCh <- err}}()}wg.Wait()curSuccesses := batchSize - len(errCh)successes += curSuccessesif len(errCh) > 0 {return successes, <-errCh}remaining -= batchSize}return successes, nil }

rsc.podControl.CreatePodsWithControllerRef

前面定義的創建pod時調用的方法為rsc.podControl.CreatePodsWithControllerRef。

func (r RealPodControl) CreatePodsWithControllerRef(namespace string, template *v1.PodTemplateSpec, controllerObject runtime.Object, controllerRef *metav1.OwnerReference) error {if err := validateControllerRef(controllerRef); err != nil {return err}return r.createPods("", namespace, template, controllerObject, controllerRef) }func (r RealPodControl) createPods(nodeName, namespace string, template *v1.PodTemplateSpec, object runtime.Object, controllerRef *metav1.OwnerReference) error {pod, err := GetPodFromTemplate(template, object, controllerRef)if err != nil {return err}if len(nodeName) != 0 {pod.Spec.NodeName = nodeName}if len(labels.Set(pod.Labels)) == 0 {return fmt.Errorf("unable to create pods, no labels")}newPod, err := r.KubeClient.CoreV1().Pods(namespace).Create(pod)if err != nil {// only send an event if the namespace isn't terminatingif !apierrors.HasStatusCause(err, v1.NamespaceTerminatingCause) {r.Recorder.Eventf(object, v1.EventTypeWarning, FailedCreatePodReason, "Error creating: %v", err)}return err}accessor, err := meta.Accessor(object)if err != nil {klog.Errorf("parentObject does not have ObjectMeta, %v", err)return nil}klog.V(4).Infof("Controller %v created pod %v", accessor.GetName(), newPod.Name)r.Recorder.Eventf(object, v1.EventTypeNormal, SuccessfulCreatePodReason, "Created pod: %v", newPod.Name)return nil }

2.2 刪除邏輯代碼塊

主要邏輯：
（1）運算獲取需要刪除的pod數量，并設置數量上限500；
（2）根據要縮容刪除的pod數量，先調用getPodsToDelete函數找出需要刪除的pod列表；
（3）調用rsc.expectations.ExpectCreations，將本輪調諧期望刪除的pod數量設置進expectations；
（4）每個pod拉起一個goroutine，調用rsc.podControl.DeletePod來刪除該pod；
（5）對于刪除失敗的pod，會調用rsc.expectations.DeletionObserved方法，減去本輪調諧中期望創建的pod數量。
至于為什么要減，原因跟上面創建邏輯代碼塊中分析的一樣。
（6）等待所有gorouutine完成，return返回。

if diff > rsc.burstReplicas {diff = rsc.burstReplicas}glog.V(2).Infof("Too many replicas for %v %s/%s, need %d, deleting %d", rsc.Kind, rs.Namespace, rs.Name, *(rs.Spec.Replicas), diff)// Choose which Pods to delete, preferring those in earlier phases of startup.podsToDelete := getPodsToDelete(filteredPods, diff)rsc.expectations.ExpectDeletions(rsKey, getPodKeys(podsToDelete))errCh := make(chan error, diff)var wg sync.WaitGroupwg.Add(diff)for _, pod := range podsToDelete {go func(targetPod *v1.Pod) {defer wg.Done()if err := rsc.podControl.DeletePod(rs.Namespace, targetPod.Name, rs); err != nil {// Decrement the expected number of deletes because the informer won't observe this deletionpodKey := controller.PodKey(targetPod)glog.V(2).Infof("Failed to delete %v, decrementing expectations for %v %s/%s", podKey, rsc.Kind, rs.Namespace, rs.Name)rsc.expectations.DeletionObserved(rsKey, podKey)errCh <- err}}(pod)}wg.Wait()select {case err := <-errCh:// all errors have been reported before and they're likely to be the same, so we'll only return the first one we hit.if err != nil {return err}default:}

2.2.1 getPodsToDelete

getPodsToDelete：根據要縮容刪除的pod數量，然后返回需要刪除的pod列表。

// pkg/controller/replicaset/replica_set.go func getPodsToDelete(filteredPods, relatedPods []*v1.Pod, diff int) []*v1.Pod {// No need to sort pods if we are about to delete all of them.// diff will always be <= len(filteredPods), so not need to handle > case.if diff < len(filteredPods) {podsWithRanks := getPodsRankedByRelatedPodsOnSameNode(filteredPods, relatedPods)sort.Sort(podsWithRanks)}return filteredPods[:diff] }func getPodsRankedByRelatedPodsOnSameNode(podsToRank, relatedPods []*v1.Pod) controller.ActivePodsWithRanks {podsOnNode := make(map[string]int)for _, pod := range relatedPods {if controller.IsPodActive(pod) {podsOnNode[pod.Spec.NodeName]++}}ranks := make([]int, len(podsToRank))for i, pod := range podsToRank {ranks[i] = podsOnNode[pod.Spec.NodeName]}return controller.ActivePodsWithRanks{Pods: podsToRank, Rank: ranks} }

篩選要刪除的pod邏輯

按照下面的排序規則，從上到下進行排序，各個條件相互互斥，符合其中一個條件則排序完成：
（1）優先刪除沒有綁定node的pod；
（2）優先刪除處于Pending狀態的pod，然后是Unknown，最后才是Running；
（3）優先刪除Not ready的pod，然后才是ready的pod；
（4）按同node上所屬replicaset的pod數量排序，優先刪除所屬replicaset的pod數量多的node上的pod；
（5）按pod ready的時間排序，優先刪除ready時間最短的pod；
（6）優先刪除pod中容器重啟次數較多的pod；
（7）按pod創建時間排序，優先刪除創建時間最短的pod。

// pkg/controller/controller_utils.go func (s ActivePodsWithRanks) Less(i, j int) bool {// 1. Unassigned < assigned// If only one of the pods is unassigned, the unassigned one is smallerif s.Pods[i].Spec.NodeName != s.Pods[j].Spec.NodeName && (len(s.Pods[i].Spec.NodeName) == 0 || len(s.Pods[j].Spec.NodeName) == 0) {return len(s.Pods[i].Spec.NodeName) == 0}// 2. PodPending < PodUnknown < PodRunningif podPhaseToOrdinal[s.Pods[i].Status.Phase] != podPhaseToOrdinal[s.Pods[j].Status.Phase] {return podPhaseToOrdinal[s.Pods[i].Status.Phase] < podPhaseToOrdinal[s.Pods[j].Status.Phase]}// 3. Not ready < ready// If only one of the pods is not ready, the not ready one is smallerif podutil.IsPodReady(s.Pods[i]) != podutil.IsPodReady(s.Pods[j]) {return !podutil.IsPodReady(s.Pods[i])}// 4. Doubled up < not doubled up// If one of the two pods is on the same node as one or more additional// ready pods that belong to the same replicaset, whichever pod has more// colocated ready pods is lessif s.Rank[i] != s.Rank[j] {return s.Rank[i] > s.Rank[j]}// TODO: take availability into account when we push minReadySeconds information from deployment into pods,// see https://github.com/kubernetes/kubernetes/issues/22065// 5. Been ready for empty time < less time < more time// If both pods are ready, the latest ready one is smallerif podutil.IsPodReady(s.Pods[i]) && podutil.IsPodReady(s.Pods[j]) {readyTime1 := podReadyTime(s.Pods[i])readyTime2 := podReadyTime(s.Pods[j])if !readyTime1.Equal(readyTime2) {return afterOrZero(readyTime1, readyTime2)}}// 6. Pods with containers with higher restart counts < lower restart countsif maxContainerRestarts(s.Pods[i]) != maxContainerRestarts(s.Pods[j]) {return maxContainerRestarts(s.Pods[i]) > maxContainerRestarts(s.Pods[j])}// 7. Empty creation time pods < newer pods < older podsif !s.Pods[i].CreationTimestamp.Equal(&s.Pods[j].CreationTimestamp) {return afterOrZero(&s.Pods[i].CreationTimestamp, &s.Pods[j].CreationTimestamp)}return false }

2.2.2 rsc.podControl.DeletePod

刪除pod的方法。

// pkg/controller/controller_utils.go func (r RealPodControl) DeletePod(namespace string, podID string, object runtime.Object) error {accessor, err := meta.Accessor(object)if err != nil {return fmt.Errorf("object does not have ObjectMeta, %v", err)}klog.V(2).Infof("Controller %v deleting pod %v/%v", accessor.GetName(), namespace, podID)if err := r.KubeClient.CoreV1().Pods(namespace).Delete(podID, nil); err != nil && !apierrors.IsNotFound(err) {r.Recorder.Eventf(object, v1.EventTypeWarning, FailedDeletePodReason, "Error deleting: %v", err)return fmt.Errorf("unable to delete pods: %v", err)}r.Recorder.Eventf(object, v1.EventTypeNormal, SuccessfulDeletePodReason, "Deleted pod: %v", podID)return nil }

3 calculateStatus

calculateStatus函數計算并返回replicaset對象的status。

怎么計算status呢？
（1）根據現存pod數量、Ready狀態的pod數量、availabel狀態的pod數量等，給replicaset對象的status的Replicas、ReadyReplicas、AvailableReplicas等字段賦值；
（2）根據replicaset對象現有status中的condition配置以及前面調用rsc.manageReplicas方法后是否有錯誤，來決定給status新增condition或移除condition，conditionType為ReplicaFailure。

當調用rsc.manageReplicas方法出錯，且replicaset對象的status中，沒有conditionType為ReplicaFailure的condition，則新增conditionType為ReplicaFailure的condition，表示該replicaset創建/刪除pod出錯；
當調用rsc.manageReplicas方法沒有任何錯誤，且replicaset對象的status中，有conditionType為ReplicaFailure的condition，則去除該condition，表示該replicaset創建/刪除pod成功。

func calculateStatus(rs *apps.ReplicaSet, filteredPods []*v1.Pod, manageReplicasErr error) apps.ReplicaSetStatus {newStatus := rs.Status// Count the number of pods that have labels matching the labels of the pod// template of the replica set, the matching pods may have more// labels than are in the template. Because the label of podTemplateSpec is// a superset of the selector of the replica set, so the possible// matching pods must be part of the filteredPods.fullyLabeledReplicasCount := 0readyReplicasCount := 0availableReplicasCount := 0templateLabel := labels.Set(rs.Spec.Template.Labels).AsSelectorPreValidated()for _, pod := range filteredPods {if templateLabel.Matches(labels.Set(pod.Labels)) {fullyLabeledReplicasCount++}if podutil.IsPodReady(pod) {readyReplicasCount++if podutil.IsPodAvailable(pod, rs.Spec.MinReadySeconds, metav1.Now()) {availableReplicasCount++}}}failureCond := GetCondition(rs.Status, apps.ReplicaSetReplicaFailure)if manageReplicasErr != nil && failureCond == nil {var reason stringif diff := len(filteredPods) - int(*(rs.Spec.Replicas)); diff < 0 {reason = "FailedCreate"} else if diff > 0 {reason = "FailedDelete"}cond := NewReplicaSetCondition(apps.ReplicaSetReplicaFailure, v1.ConditionTrue, reason, manageReplicasErr.Error())SetCondition(&newStatus, cond)} else if manageReplicasErr == nil && failureCond != nil {RemoveCondition(&newStatus, apps.ReplicaSetReplicaFailure)}newStatus.Replicas = int32(len(filteredPods))newStatus.FullyLabeledReplicas = int32(fullyLabeledReplicasCount)newStatus.ReadyReplicas = int32(readyReplicasCount)newStatus.AvailableReplicas = int32(availableReplicasCount)return newStatus }

4 updateReplicaSetStatus

主要邏輯：
（1）判斷新計算出來的status中的各個屬性如Replicas、ReadyReplicas、AvailableReplicas以及Conditions是否與現存replicaset對象的status中的一致，一致則不用做更新操作，直接return；
（2）調用c.UpdateStatus更新replicaset的status。

// pkg/controller/replicaset/replica_set_utils.go func updateReplicaSetStatus(c appsclient.ReplicaSetInterface, rs *apps.ReplicaSet, newStatus apps.ReplicaSetStatus) (*apps.ReplicaSet, error) {// This is the steady state. It happens when the ReplicaSet doesn't have any expectations, since// we do a periodic relist every 30s. If the generations differ but the replicas are// the same, a caller might've resized to the same replica count.if rs.Status.Replicas == newStatus.Replicas &&rs.Status.FullyLabeledReplicas == newStatus.FullyLabeledReplicas &&rs.Status.ReadyReplicas == newStatus.ReadyReplicas &&rs.Status.AvailableReplicas == newStatus.AvailableReplicas &&rs.Generation == rs.Status.ObservedGeneration &&reflect.DeepEqual(rs.Status.Conditions, newStatus.Conditions) {return rs, nil}// Save the generation number we acted on, otherwise we might wrongfully indicate// that we've seen a spec update when we retry.// TODO: This can clobber an update if we allow multiple agents to write to the// same status.newStatus.ObservedGeneration = rs.Generationvar getErr, updateErr errorvar updatedRS *apps.ReplicaSetfor i, rs := 0, rs; ; i++ {klog.V(4).Infof(fmt.Sprintf("Updating status for %v: %s/%s, ", rs.Kind, rs.Namespace, rs.Name) +fmt.Sprintf("replicas %d->%d (need %d), ", rs.Status.Replicas, newStatus.Replicas, *(rs.Spec.Replicas)) +fmt.Sprintf("fullyLabeledReplicas %d->%d, ", rs.Status.FullyLabeledReplicas, newStatus.FullyLabeledReplicas) +fmt.Sprintf("readyReplicas %d->%d, ", rs.Status.ReadyReplicas, newStatus.ReadyReplicas) +fmt.Sprintf("availableReplicas %d->%d, ", rs.Status.AvailableReplicas, newStatus.AvailableReplicas) +fmt.Sprintf("sequence No: %v->%v", rs.Status.ObservedGeneration, newStatus.ObservedGeneration))rs.Status = newStatusupdatedRS, updateErr = c.UpdateStatus(rs)if updateErr == nil {return updatedRS, nil}// Stop retrying if we exceed statusUpdateRetries - the replicaSet will be requeued with a rate limit.if i >= statusUpdateRetries {break}// Update the ReplicaSet with the latest resource version for the next pollif rs, getErr = c.Get(rs.Name, metav1.GetOptions{}); getErr != nil {// If the GET fails we can't trust status.Replicas anymore. This error// is bound to be more interesting than the update failure.return nil, getErr}}return nil, updateErr }

c.UpdateStatus

// staging/src/k8s.io/client-go/kubernetes/typed/apps/v1/replicaset.go func (c *replicaSets) UpdateStatus(replicaSet *v1.ReplicaSet) (result *v1.ReplicaSet, err error) {result = &v1.ReplicaSet{}err = c.client.Put().Namespace(c.ns).Resource("replicasets").Name(replicaSet.Name).SubResource("status").Body(replicaSet).Do().Into(result)return }

總結

replicaset controller架構圖

replicaset controller的大致組成和處理流程如下圖，replicaset controller對pod和replicaset對象注冊了event handler，當有事件時，會watch到然后將對應的replicaset對象放入到queue中，然后syncReplicaSet方法為replicaset controller調諧replicaset對象的核心處理邏輯所在，從queue中取出replicaset對象，做調諧處理。

replicaset controller核心處理邏輯

replicaset controller的核心處理邏輯是根據replicaset對象里期望的pod數量以及現存pod數量的比較，當期望pod數量比現存pod數量多時，調用創建pod算法創建出新的pod，直至達到期望數量；當期望pod數量比現存pod數量少時，調用刪除pod算法，并根據一定的策略對現存pod列表做排序，從中按順序選擇多余的pod然后刪除，直至達到期望數量。

replicaset controller創建pod算法

replicaset controller創建pod的算法是，按1、2、4、8…的遞增趨勢分多批次進行（每次調諧中創建pod的數量上限為500個，超過上限的會在下次調諧中再創建），若某批次創建pod有失敗的（如apiserver限流，丟棄請求等，注意：超時除外，因為initialization處理有可能超時），則后續批次的pod創建不再進行，需等待該repliaset對象下次調諧時再觸發該pod創建算法，進行pod的創建，直至達到期望數量。

replicaset controller刪除pod算法

replicaset controller刪除pod的算法是，先根據一定的策略將現存pod列表做排序，然后按順序從中選擇指定數量的pod，拉起與要刪除的pod數量相同的goroutine來刪除pod（每次調諧中刪除pod的數量上限為500個），并等待所有goroutine執行完成。刪除pod有失敗的（如apiserver限流，丟棄請求）或超過500上限的部分，需等待該repliaset對象下次調諧時再觸發該pod刪除算法，進行pod的刪除，直至達到期望數量。

篩選要刪除的pod邏輯

按照下面的排序規則，從上到下進行排序，各個條件相互互斥，符合其中一個條件則排序完成：
（1）優先刪除沒有綁定node的pod；
（2）優先刪除處于Pending狀態的pod，然后是Unknown，最后才是Running；
（3）優先刪除Not ready的pod，然后才是ready的pod；
（4）按同node上所屬replicaset的pod數量排序，優先刪除所屬replicaset的pod數量多的node上的pod；
（5）按pod ready的時間排序，優先刪除ready時間最短的pod；
（6）優先刪除pod中容器重啟次數較多的pod；
（7）按pod創建時間排序，優先刪除創建時間最短的pod。

expectations機制

關于expectations機制的分析，會在下一篇博客中進行。

總結

以上是生活随笔為你收集整理的k8s replicaset controller源码分析（2）-核心处理逻辑分析的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。