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# P5-StatefulSet Controller
## 前言
在前面的几篇文章中，先对deployment controller进行了初步分析:
[Controller-P3-Deployment Controller](https://github.com/yinwenqin/kubeSourceCodeNote/blob/master/controller/Kubernetes源码学习-Controller-P3-Controller分类与Deployment Controller.md)
严格来讲deployment的管理pod的逻辑是基于replicaSet来实现的，因此接下来结合replicaSet controller进行了深入:
[Controller-P3-ReplicaSet Controller](https://github.com/yinwenqin/kubeSourceCodeNote/blob/master/controller/Kubernetes源码学习-Controller-P4-ReplicaSet Controller.md)
那么在本篇，来看看另一个最常用的承载在pod之上的管理单位的控制器实现: **StatefulSet Controller**
##StatefulSet 的基本特性
在看代码之前，先回顾一下sts的基本运行特性，代入地阅读代码会比较顺畅
**创建**
sts是有序的，pod副本有序串行地新建，pod名称为{sts_name}-{0..N}，从小序号的pod(名称为{sts_name}-0)创建，一直到第n个副本的pod(名称为{sts_name}-n)
**更新**
sts的更新策略有2种:
- `RollingUpdateStatefulSetStrategyType`，默认的滚动更新策略，此策略下，更新时pod根据序号反顺序更新，从最大序号的pod开始删除重建，更新至序号最小的pod。更新过程中，始终保持pod数量等于指定副本数，即每删除一个pod，才会再创建一个。同时可以指定一个**partition**参数，指定这个参数后，只有序号大于等于partition的pod才会被更新，序号小于partition参数的pod不会被更新，例如有5个副本，partition设置为2，那么在更新sts时，0和1号pod不会更新，2 3 4号pod则会更新重建；此时继续将partition缩减为0，则0 1号pod也会更新重建。默认partition为0，即所有的pod都会更新。这个参数一般不会使用，但可用在发布时动态更新递减partition的值，来实现滚动灰度发布。
- `OnDeleteStatefulSetStrategyType`, 此策略下controller不会对pod做任何操作，由手动删除pod来触发新pod的创建
**删除**
删除sts时，可以指定级联模式的参数`--cascade=true`，默认为true，意思是删除sts会同时删除它所管理的pod。设置为false时，删除sts不会影响pod的运行，且sts重建后依然能与此前的pod关联起来(这种方式可能会产生孤儿pod)。
**关联关系**
先来看看sts和pod的关联方式:
```bash
# sts
[root@008019 ~]# kubectl get sts deptest11dev
NAME READY AGE
deptest11dev 2/2 99d
# pod
[root@008019 ~]# kubectl get pods | grep deptest11dev
deptest11dev-0 1/1 Running 1 99d
deptest11dev-1 1/1 Running 0 3d17h
# edit pod
# 可以查看到pod的ownerReferences字段，与sts关联
ownerReferences:
- apiVersion: apps/v1
blockOwnerDeletion: true
controller: true
kind: StatefulSet
name: deptest11dev
uid: 28ecf735-2ab4-11ea-afa8-1866daf0f324
# 可以查看到pod的labels标签，新增了一个controller-revision-hash标签，与controllerRevision关联
labels:
app: deptest11dev
controller-revision-hash: deptest11dev-587f8bd845
statefulset.kubernetes.io/pod-name: deptest11dev-1
```
再来看看sts和ControllerRevision关联方式:
```bash
[root@008019 ~]# kubectl get sts deptest11dev
NAME READY AGE
deptest11dev 2/2 99d
[root@008019 ~]# kubectl get ControllerRevisions | grep deptest11dev
deptest11dev-587f8bd845 statefulset.apps/deptest11dev 1 99d
[root@008019 ~]# kubectl get ControllerRevisions deptest11dev-587f8bd845
NAME CONTROLLER REVISION AGE
deptest11dev-587f8bd845 statefulset.apps/deptest11dev 1 99d
# ControllerRevisions资源中的ownerReferences字段,可以看出sts与其通过这个字段关联
ownerReferences:
- apiVersion: apps/v1
blockOwnerDeletion: true
controller: true
kind: StatefulSet
name: deptest11dev
uid: 28ecf735-2ab4-11ea-afa8-1866daf0f324
# sts status字段,可以看出sts通过status下的currentRevision、updateRevision字段与ControllerRevision关联
status:
collisionCount: 0
currentReplicas: 2
currentRevision: deptest11dev-587f8bd845
observedGeneration: 3
readyReplicas: 2
replicas: 2
updateRevision: deptest11dev-587f8bd845
updatedReplicas: 2
# 对sts.spec字段里的内容更新后引起pod重建，sts开始滚动更新，此时sts的status字段内容如下:
status:
collisionCount: 0
currentReplicas: 1
currentRevision: deptest11dev-587f8bd845
observedGeneration: 4
readyReplicas: 2
replicas: 2
# 这时可以发现updateRevision字段更新为了新的revision，即updateRevision是最近一次更新的Revision
updateRevision: deptest11dev-7487498978
# 修改sts进行缩容/扩容 时的status字段：
status:
collisionCount: 0
currentReplicas: 3
currentRevision: deptest11dev-7487498978
observedGeneration: 5
readyReplicas: 3
replicas: 3
# revision不会更新
updateRevision: deptest11dev-7487498978
updatedReplicas: 3
```
**记住这几者之间双向地关联方式，下面会提到。**
## StatefulSet Controller
### 初始化
`cmd/kube-controller-manager/app/apps.go:59`
```go
func startStatefulSetController(ctx ControllerContext) (http.Handler, bool, error) {
if !ctx.AvailableResources[schema.GroupVersionResource{Group: "apps", Version: "v1", Resource: "statefulsets"}] {
return nil, false, nil
}
go statefulset.NewStatefulSetController(
ctx.InformerFactory.Core().V1().Pods(),
ctx.InformerFactory.Apps().V1().StatefulSets(),
ctx.InformerFactory.Core().V1().PersistentVolumeClaims(),
ctx.InformerFactory.Apps().V1().ControllerRevisions(),
ctx.ClientBuilder.ClientOrDie("statefulset-controller"),
).Run(1, ctx.Stop)
return nil, true, nil
}
```
先来看看`NewStatefulSetController`做了什么：
==> `pkg/controller/statefulset/stateful_set.go:81`
```go
func NewStatefulSetController(
// 1.StatefulSetController关注四种类型的资源: Pod/Sts/PVC/ControllerRevision
podInformer coreinformers.PodInformer,
setInformer appsinformers.StatefulSetInformer,
pvcInformer coreinformers.PersistentVolumeClaimInformer,
revInformer appsinformers.ControllerRevisionInformer,
kubeClient clientset.Interface,
) *StatefulSetController {
eventBroadcaster := record.NewBroadcaster()
eventBroadcaster.StartLogging(klog.Infof)
eventBroadcaster.StartRecordingToSink(&v1core.EventSinkImpl{Interface: kubeClient.CoreV1().Events("")})
recorder := eventBroadcaster.NewRecorder(scheme.Scheme, v1.EventSource{Component: "statefulset-controller"})
// 2.NewDefaultStatefulSetControl方法需要关注
ssc := &StatefulSetController{
kubeClient: kubeClient,
control: NewDefaultStatefulSetControl(
NewRealStatefulPodControl(
kubeClient,
setInformer.Lister(),
podInformer.Lister(),
pvcInformer.Lister(),
recorder),
NewRealStatefulSetStatusUpdater(kubeClient, setInformer.Lister()),
history.NewHistory(kubeClient, revInformer.Lister()),
recorder,
),
pvcListerSynced: pvcInformer.Informer().HasSynced,
queue: workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "statefulset"),
podControl: controller.RealPodControl{KubeClient: kubeClient, Recorder: recorder},
revListerSynced: revInformer.Informer().HasSynced,
}
// 当sts管理的pod curd时对应的处理方法(按入workqueue/更新pod/删除pod)
podInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
// lookup the statefulset and enqueue
AddFunc: ssc.addPod,
// lookup current and old statefulset if labels changed
UpdateFunc: ssc.updatePod,
// lookup statefulset accounting for deletion tombstones
DeleteFunc: ssc.deletePod,
})
ssc.podLister = podInformer.Lister()
ssc.podListerSynced = podInformer.Informer().HasSynced
// 当sts curd时对应的方法(sts压入workqueue)
setInformer.Informer().AddEventHandlerWithResyncPeriod(
cache.ResourceEventHandlerFuncs{
AddFunc: ssc.enqueueStatefulSet,
UpdateFunc: func(old, cur interface{}) {
oldPS := old.(*apps.StatefulSet)
curPS := cur.(*apps.StatefulSet)
if oldPS.Status.Replicas != curPS.Status.Replicas {
klog.V(4).Infof("Observed updated replica count for StatefulSet: %v, %d->%d", curPS.Name, oldPS.Status.Replicas, curPS.Status.Replicas)
}
ssc.enqueueStatefulSet(cur)
},
DeleteFunc: ssc.enqueueStatefulSet,
},
statefulSetResyncPeriod,
)
ssc.setLister = setInformer.Lister()
ssc.setListerSynced = setInformer.Informer().HasSynced
// TODO: Watch volumes
// 返回ssc(StatefulSetController)
return ssc
}
```
先看注释1，可以发现，StatefulSetController关注四种类型的资源: Pod/Sts/PVC/ControllerRevision，其中的**ControllerRevision**不太熟悉，先找出来看下它的结构，逐级跳转:
`cmd/kube-controller-manager/app/apps.go:63`
==> `vendor/k8s.io/client-go/informers/apps/v1/interface.go:28`
==>`vendor/k8s.io/client-go/informers/apps/v1/controllerrevision.go:38`
==> `vendor/k8s.io/client-go/listers/apps/v1/controllerrevision.go:29`
==> `vendor/k8s.io/api/apps/v1/types.go:800`
```go
type ControllerRevision struct {
metav1.TypeMeta `json:",inline"`
// Standard object's metadata.
// More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
// +optional
metav1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`
// Data is the serialized representation of the state.
Data runtime.RawExtension `json:"data,omitempty" protobuf:"bytes,2,opt,name=data"`
// Revision indicates the revision of the state represented by Data.
Revision int64 `json:"revision" protobuf:"varint,3,opt,name=revision"`
}
```
阅读这个结构体上方的注释可以得知，ControllerRevision提供给DaemonSet和StatefulSet用作更新和回滚，ControllerRevision存放的是数据的快照，ControllerRevision生成之后内容是不可修改的，由调用端来负责序列化写入和反序列化读取。其中Revision(int64)字段相当于ControllerRevision的版本id号，Data字段则存放序列化后的数据。
**画外音：不难猜测，StatefulSet的更新以及回滚(也是一种特殊的更新)操作，是基于对新旧ControllerRevision的对比来进行的**
在来看下注释2，NewDefaultStatefulSetControl方法:
`pkg/controller/statefulset/stateful_set.go:95`
==> `pkg/controller/statefulset/stateful_set_control.go:54`
```go
func NewDefaultStatefulSetControl(
podControl StatefulPodControlInterface,
statusUpdater StatefulSetStatusUpdaterInterface,
controllerHistory history.Interface,
recorder record.EventRecorder) StatefulSetControlInterface {
return &defaultStatefulSetControl{podControl, statusUpdater, controllerHistory, recorder}
}
```
**NewDefaultStatefulSetControl**返回的**defaultStatefulSetControl**结构体对象是sts管理控制逻辑的语义实现，**defaultStatefulSetControl**结构体里面包含了sts控制过程中的各种接口：
1. 管理sts对应的pod/pvc(podControl)的方法接口，有(**CreateStatefulPod/UpdateStatefulPod/DeleteStatefulPod**)这几个方法，通过**NewRealStatefulPodControl**函数返回的**realStatefulPodControl**结构体对象来实现
2. 管理sts status状态的更新(statusUpdater)的方法接口，有**UpdateStatefulSetStatus**这一个方法，通过**NewRealStatefulSetStatusUpdater**返回的**realStatefulSetStatusUpdater**结构体对象来实现。
3. 管理ControllerRevision版本(controllerHistory) 的方法接口，有(**ListControllerRevisions/CreateControllerRevision/DeleteControllerRevision/UpdateControllerRevision/AdoptControllerRevision/ReleaseControllerRevision**)这几个方法，通过***history.NewHistory***返回的**realHistory**结构体对象来实现。
现在接着往下，去看看ssc(StatefulSetController) 运行的Run函数。
### 工作过程
`*StatefulSetController.Run()`函数：
```go
func (ssc *StatefulSetController) Run(workers int, stopCh <-chan struct{}) {
defer utilruntime.HandleCrash()
defer ssc.queue.ShutDown()
klog.Infof("Starting stateful set controller")
defer klog.Infof("Shutting down statefulset controller")
if !controller.WaitForCacheSync("stateful set", stopCh, ssc.podListerSynced, ssc.setListerSynced, ssc.pvcListerSynced, ssc.revListerSynced) {
return
}
for i := 0; i < workers; i++ {
go wait.Until(ssc.worker, time.Second, stopCh)
}
<-stopCh
}
```
wait.Until定时器前面已经讲过，不再复述，重点在于ssc.worker函数，代码里有多次跳跃：
`pkg/controller/statefulset/stateful_set.go:159`
==>`pkg/controller/statefulset/stateful_set.go:410`
==> `pkg/controller/statefulset/stateful_set.go:399`
==>`pkg/controller/statefulset/stateful_set.go:415`
```go
// sync syncs the given statefulset.
func (ssc *StatefulSetController) sync(key string) error {
startTime := time.Now()
defer func() {
klog.V(4).Infof("Finished syncing statefulset %q (%v)", key, time.Since(startTime))
}()
// key的样例: default/teststs，做个切割，拿到namespace和sts name
namespace, name, err := cache.SplitMetaNamespaceKey(key)
if err != nil {
return err
}
// 获取到sts对象
set, err := ssc.setLister.StatefulSets(namespace).Get(name)
if errors.IsNotFound(err) {
klog.Infof("StatefulSet has been deleted %v", key)
return nil
}
if err != nil {
utilruntime.HandleError(fmt.Errorf("unable to retrieve StatefulSet %v from store: %v", key, err))
return err
}
// labelSelector
selector, err := metav1.LabelSelectorAsSelector(set.Spec.Selector)
if err != nil {
utilruntime.HandleError(fmt.Errorf("error converting StatefulSet %v selector: %v", key, err))
// This is a non-transient error, so don't retry.
return nil
}
// 孤儿Revisions修正托管
if err := ssc.adoptOrphanRevisions(set); err != nil {
return err
}
// 获取到sts管理的pod
pods, err := ssc.getPodsForStatefulSet(set, selector)
if err != nil {
return err
}
// syncStatefulSet 执行sts sync
return ssc.syncStatefulSet(set, pods)
}
```
来分步看下
#### 孤儿Revisions修正托管
上面指出sts和revision两者之间显示地双向指定字段来关联对方，明白这一点那么这个函数就好理解了。
出现孤儿ControllerRevisions的原因，很有可能是sts在此期间进行了反复的更新，更新时间差之中产生了脏数据.
`pkg/controller/statefulset/stateful_set.go:316`
```go
// adoptOrphanRevisions adopts any orphaned ControllerRevisions matched by set's Selector.
func (ssc *StatefulSetController) adoptOrphanRevisions(set *apps.StatefulSet) error {
// 通过sts指定的revision相关字段找到对应的revisions
revisions, err := ssc.control.ListRevisions(set)
if err != nil {
return err
}
hasOrphans := false
for i := range revisions {
// 通过revision指定的controller来源，来找sts。如果指定绑定的sts为空，那么说明此ControllerRevisions是孤儿状态(无托管)，需要回收
if metav1.GetControllerOf(revisions[i]) == nil {
hasOrphans = true
break
}
}
// 出现孤儿ControllerRevisions的原因，很有可能是sts在此期间进行了反复的更新，因此重新获取一次最新的sts
if hasOrphans {
fresh, err := ssc.kubeClient.AppsV1().StatefulSets(set.Namespace).Get(set.Name, metav1.GetOptions{})
if err != nil {
return err
}
// sts(old) 若与fresh sts uid不同，则说明期间sts可能经历了删除重建，本次逻辑的流程打破，抛错返回
if fresh.UID != set.UID {
return fmt.Errorf("original StatefulSet %v/%v is gone: got uid %v, wanted %v", set.Namespace, set.Name, fresh.UID, set.UID)
}
// 为这些controller sts指定为空的revision，若label匹配则加上ownerReferences sts指定，若label不匹配则gc
return ssc.control.AdoptOrphanRevisions(set, revisions)
}
return nil
}
```
#### 获取到sts管理的pod
`pkg/controller/statefulset/stateful_set.go:285`
```go
func (ssc *StatefulSetController) getPodsForStatefulSet(set *apps.StatefulSet, selector labels.Selector) ([]*v1.Pod, error) {
// List all pods to include the pods that don't match the selector anymore but
// has a ControllerRef pointing to this StatefulSet.
pods, err := ssc.podLister.Pods(set.Namespace).List(labels.Everything())
if err != nil {
return nil, err
}
// filter函数的作用是判断指定的pod和sts是否有所属关系，展开代码可以看到判断的方式很简单，对pod的名称做re字符串切割，最后一个"-"之前的字符串是parent，之后的数字是序号索引，判断parent与sts name是否一致，一致则为true，pod 属于 sts，不一致则为false
filter := func(pod *v1.Pod) bool {
// Only claim if it matches our StatefulSet name. Otherwise release/ignore.
return isMemberOf(set, pod)
}
// 如同revision一样，若存在孤儿pod，也需要对孤儿pod进行收养，与sts label匹配则加上关联，label不匹配则解除关联。
canAdoptFunc := controller.RecheckDeletionTimestamp(func() (metav1.Object, error) {
fresh, err := ssc.kubeClient.AppsV1().StatefulSets(set.Namespace).Get(set.Name, metav1.GetOptions{})
if err != nil {
return nil, err
}
if fresh.UID != set.UID {
return nil, fmt.Errorf("original StatefulSet %v/%v is gone: got uid %v, wanted %v", set.Namespace, set.Name, fresh.UID, set.UID)
}
return fresh, nil
})
cm := controller.NewPodControllerRefManager(ssc.podControl, set, selector, controllerKind, canAdoptFunc)
// 执行筛选
return cm.ClaimPods(pods, filter)
}
```
**ClaimPods**
`pkg/controller/controller_ref_manager.go:171`
```go
func (m *PodControllerRefManager) ClaimPods(pods []*v1.Pod, filters ...func(*v1.Pod) bool) ([]*v1.Pod, error) {
var claimed []*v1.Pod
var errlist []error
match := func(obj metav1.Object) bool {
pod := obj.(*v1.Pod)
// 先根据标签匹配pod，仅当标签匹配通过后，再匹配下一步（sts调用则是按照上面说的取 pod name 字符串切割后与sts name对比）
if !m.Selector.Matches(labels.Set(pod.Labels)) {
return false
}
for _, filter := range filters {
if !filter(pod) {
return false
}
}
return true
}
adopt := func(obj metav1.Object) error {
// 收养pod(添加关联关系)，即为pod.metadata patch ownerReferences字段。
return m.AdoptPod(obj.(*v1.Pod))
}
release := func(obj metav1.Object) error {
// 释放pod关联关系，即为pod.metadata delete ownerReferences字段。
return m.ReleasePod(obj.(*v1.Pod))
}
for _, pod := range pods {
// 判断单个pod是否匹配，收养/释放孤儿pod的函数ClaimObject
ok, err := m.ClaimObject(pod, match, adopt, release)
if err != nil {
errlist = append(errlist, err)
continue
}
if ok {
claimed = append(claimed, pod)
}
}
return claimed, utilerrors.NewAggregate(errlist)
}
```
####
####ClaimObject
`pkg/controller/controller_ref_manager.go:66`
```go
func (m *BaseControllerRefManager) ClaimObject(obj metav1.Object, match func(metav1.Object) bool, adopt, release func(metav1.Object) error) (bool, error) {
// 1 获取到pod.metadata中的ownerReferences字段
controllerRef := metav1.GetControllerOf(obj)
// 1-1 如果pod存在ownerReferences,则直接进入判断是否match
if controllerRef != nil {
if controllerRef.UID != m.Controller.GetUID() {
// Owned by someone else. Ignore.
return false, nil
}
// 1-2 匹配则返回true
if match(obj) {
return true, nil
}
if m.Controller.GetDeletionTimestamp() != nil {
return false, nil
}
// 1-3 不匹配则pod释放关联字段,返回false
if err := release(obj); err != nil {
// If the pod no longer exists, ignore the error.
if errors.IsNotFound(err) {
return false, nil
}
return false, err
}
// Successfully released.
return false, nil
}
// 2 孤儿pod，则要根据情况判断是否收养/释放
// 2-1 已删除的sts或match规则不匹配，返回false
if m.Controller.GetDeletionTimestamp() != nil || !match(obj) {
// Ignore if we're being deleted or selector doesn't match.
return false, nil
}
if obj.GetDeletionTimestamp() != nil {
// Ignore if the object is being deleted
return false, nil
}
// Selector matches. Try to adopt.
if err := adopt(obj); err != nil {
// If the pod no longer exists, ignore the error.
if errors.IsNotFound(err) {
return false, nil
}
// Either someone else claimed it first, or there was a transient error.
// The controller should requeue and try again if it's still orphaned.
return false, err
}
// 收养成功返回true
return true, nil
}
```
到这里，所有应当被sts管理的pod(包括孤儿pod)就过滤完毕了，开始执行真正的sts sync。
#### syncStatefulSet
在找到了所有管理的pod后，就要开始sts 的sync，进行更新sts及更新pod的操作了，回到这里:
`pkg/controller/statefulset/stateful_set.go:451`
==> `pkg/controller/statefulset/stateful_set.go:458`
==> `pkg/controller/statefulset/stateful_set_control.go:75`
```go
func (ssc *defaultStatefulSetControl) UpdateStatefulSet(set *apps.StatefulSet, pods []*v1.Pod) error {
// 取出sts所有的revision并排序
revisions, err := ssc.ListRevisions(set)
if err != nil {
return err
}
history.SortControllerRevisions(revisions)
// 获得当前revision，以及更新后最新的revision
currentRevision, updateRevision, collisionCount, err := ssc.getStatefulSetRevisions(set, revisions)
if err != nil {
return err
}
// 核心方法，对pod进行操作
status, err := ssc.updateStatefulSet(set, currentRevision, updateRevision, collisionCount, pods)
if err != nil {
return err
}
// 操作完成后记录修改sts.status
err = ssc.updateStatefulSetStatus(set, status)
if err != nil {
return err
}
klog.V(4).Infof("StatefulSet %s/%s pod status replicas=%d ready=%d current=%d updated=%d",
set.Namespace,
set.Name,
status.Replicas,
status.ReadyReplicas,
status.CurrentReplicas,
status.UpdatedReplicas)
klog.V(4).Infof("StatefulSet %s/%s revisions current=%s update=%s",
set.Namespace,
set.Name,
status.CurrentRevision,
status.UpdateRevision)
// 对set的revision history进行维护
return ssc.truncateHistory(set, pods, revisions, currentRevision, updateRevision)
}
```
这里面最核心的函数是`updateStatefulSetStatus`,接着往下
#### updateStatefulSet
这一个函数内容很多，200多行代码，需要说明的地方会在下面代码中注释。
```go
func (ssc *defaultStatefulSetControl) updateStatefulSet(
set *apps.StatefulSet,
currentRevision *apps.ControllerRevision,
updateRevision *apps.ControllerRevision,
collisionCount int32,
pods []*v1.Pod) (*apps.StatefulSetStatus, error) {
// 获取到当前sts currentSet，然后获取到需更新到的sts updateSet。要实现的更新效果是：
// 1.滚动更新时，在未指定partition时，使当前sts的管理的pod缩减为0，updateSet的ready pod数 = spec.replicas
// 2.滚动更新时，在未指定partition后，大于等于partition的pod全部归于updateSet，小于partition值的pod还是归属于原currentSet
// 3.OnDelete更新时，do nothing
currentSet, err := ApplyRevision(set, currentRevision)
if err != nil {
return nil, err
}
updateSet, err := ApplyRevision(set, updateRevision)
if err != nil {
return nil, err
}
// set the generation, and revisions in the returned status
// 重新计算sts的status
status := apps.StatefulSetStatus{}
status.ObservedGeneration = set.Generation
status.CurrentRevision = currentRevision.Name
status.UpdateRevision = updateRevision.Name
status.CollisionCount = new(int32)
*status.CollisionCount = collisionCount
replicaCount := int(*set.Spec.Replicas)
// replicas是合法副本，将满足 0 <= pod序号 < sts.spec.replicas的pod,放到这个slice里来。这里面的pod都是要保证ready的
replicas := make([]*v1.Pod, replicaCount)
// condemned是非法副本，将满足 pod序号 >= sts.spec.replicas的pod,放到这个slice里来,这些pod是要删除掉的(可能是被缩容掉的)
condemned := make([]*v1.Pod, 0, len(pods))
unhealthy := 0
firstUnhealthyOrdinal := math.MaxInt32
var firstUnhealthyPod *v1.Pod
// First we partition pods into two lists valid replicas and condemned Pods
for i := range pods {
status.Replicas++
// status.ReadyReplicas计数
if isRunningAndReady(pods[i]) {
status.ReadyReplicas++
}
if isCreated(pods[i]) && !isTerminating(pods[i]) {
// 通过pod的controller-revision-hash label，判断pod属于currentSet还是UpdatedSet，分别计数
if getPodRevision(pods[i]) == currentRevision.Name {
status.CurrentReplicas++
}
if getPodRevision(pods[i]) == updateRevision.Name {
status.UpdatedReplicas++
}
}
if ord := getOrdinal(pods[i]); 0 <= ord && ord < replicaCount {
// 将满足 0 <= pod序号 < sts.spec.replicas的pod,放到replicas这个slice里来
replicas[ord] = pods[i]
} else if ord >= replicaCount {
// 将满足 pod序号 >= sts.spec.replicas的pod,放到condemned这个slice里来,这些pod是要删除掉的。
condemned = append(condemned, pods[i])
}
}
// replicas slice之中如果有索引位置为空，则需要填充相应的pod。
// 根据currentSet.replicas/UpdatedSet.replicas/partition这三个值来判断pod是基于current revision还是基于update revision创建
for ord := 0; ord < replicaCount; ord++ {
if replicas[ord] == nil {
replicas[ord] = newVersionedStatefulSetPod(
currentSet,
updateSet,
currentRevision.Name,
updateRevision.Name, ord)
}
}
// 对需要删除的非法pod按照序号从大到小的顺序排序
sort.Sort(ascendingOrdinal(condemned))
// 如果有不健康的pod，也需要删除，但还是遵循串行的原则，优先删除非法pod中序号最大的，再到合法副本中的序号最小的。
for i := range replicas {
if !isHealthy(replicas[i]) {
unhealthy++
if ord := getOrdinal(replicas[i]); ord < firstUnhealthyOrdinal {
firstUnhealthyOrdinal = ord
firstUnhealthyPod = replicas[i]
}
}
}
for i := range condemned {
if !isHealthy(condemned[i]) {
unhealthy++
if ord := getOrdinal(condemned[i]); ord < firstUnhealthyOrdinal {
firstUnhealthyOrdinal = ord
firstUnhealthyPod = condemned[i]
}
}
}
if unhealthy > 0 {
klog.V(4).Infof("StatefulSet %s/%s has %d unhealthy Pods starting with %s",
set.Namespace,
set.Name,
unhealthy,
firstUnhealthyPod.Name)
}
// If the StatefulSet is being deleted, don't do anything other than updating
// status.
if set.DeletionTimestamp != nil {
return &status, nil
}
monotonic := !allowsBurst(set)
// 根据pod的序号，对它们依次进行检查并操作。
for i := range replicas {
// 错误状态的pod删除重建
if isFailed(replicas[i]) {
ssc.recorder.Eventf(set, v1.EventTypeWarning, "RecreatingFailedPod",
"StatefulSet %s/%s is recreating failed Pod %s",
set.Namespace,
set.Name,
replicas[i].Name)
if err := ssc.podControl.DeleteStatefulPod(set, replicas[i]); err != nil {
return &status, err
}
if getPodRevision(replicas[i]) == currentRevision.Name {
status.CurrentReplicas--
}
if getPodRevision(replicas[i]) == updateRevision.Name {
status.UpdatedReplicas--
}
status.Replicas--
replicas[i] = newVersionedStatefulSetPod(
currentSet,
updateSet,
currentRevision.Name,
updateRevision.Name,
i)
}
// pod没有被创建(可能是上面刚填充的)，就创建pod
if !isCreated(replicas[i]) {
if err := ssc.podControl.CreateStatefulPod(set, replicas[i]); err != nil {
return &status, err
}
status.Replicas++
if getPodRevision(replicas[i]) == currentRevision.Name {
status.CurrentReplicas++
}
if getPodRevision(replicas[i]) == updateRevision.Name {
status.UpdatedReplicas++
}
// 如果不允许burst，直接返回
if monotonic {
return &status, nil
}
// pod created, no more work possible for this round
continue
}
// 如果不允许burst，对于终结中的pod不采取任何逻辑，等待它终结完毕后下一轮再操作。
if isTerminating(replicas[i]) && monotonic {
klog.V(4).Infof(
"StatefulSet %s/%s is waiting for Pod %s to Terminate",
set.Namespace,
set.Name,
replicas[i].Name)
return &status, nil
}
// 如果是正在创建中的pod(还未达到ready状态)，同样不采取任何操作，因为需要保证创建操作依次有序
if !isRunningAndReady(replicas[i]) && monotonic {
klog.V(4).Infof(
"StatefulSet %s/%s is waiting for Pod %s to be Running and Ready",
set.Namespace,
set.Name,
replicas[i].Name)
return &status, nil
}
// 如果此pod与sts已经匹配(ready),且存储满足sts、pod的要求，那么这个pod就是合格的pod，continue
if identityMatches(set, replicas[i]) && storageMatches(set, replicas[i]) {
continue
}
// 确保pod与sts的标签关联，以及为pod准备好它需要的pvc
replica := replicas[i].DeepCopy()
if err := ssc.podControl.UpdateStatefulPod(updateSet, replica); err != nil {
return &status, err
}
}
// 上面的合法副本得以保证之后，下面要开始按pod序号从大到小的顺序，删除非法pod了
for target := len(condemned) - 1; target >= 0; target-- {
// 终结中的pod不再处理，直接返回，等待下一轮检查
if isTerminating(condemned[target]) {
klog.V(4).Infof(
"StatefulSet %s/%s is waiting for Pod %s to Terminate prior to scale down",
set.Namespace,
set.Name,
condemned[target].Name)
// block if we are in monotonic mode
if monotonic {
return &status, nil
}
continue
}
// 如果此非法pod不是ready状态，且不允许burst，且它不是优先级第一的非健康pod，不做任何操作。换而言之，即使是删除非健康的pod，也要按照序号从大到小的顺序串行执行。
if !isRunningAndReady(condemned[target]) && monotonic && condemned[target] != firstUnhealthyPod {
klog.V(4).Infof(
"StatefulSet %s/%s is waiting for Pod %s to be Running and Ready prior to scale down",
set.Namespace,
set.Name,
firstUnhealthyPod.Name)
return &status, nil
}
// 开始删除此pod，更新status
klog.V(2).Infof("StatefulSet %s/%s terminating Pod %s for scale down",
set.Namespace,
set.Name,
condemned[target].Name)
if err := ssc.podControl.DeleteStatefulPod(set, condemned[target]); err != nil {
return &status, err
}
if getPodRevision(condemned[target]) == currentRevision.Name {
status.CurrentReplicas--
}
if getPodRevision(condemned[target]) == updateRevision.Name {
status.UpdatedReplicas--
}
if monotonic {
return &status, nil
}
}
// OnDelete更新模式下，不自动删除pod，需要手动删除pod来触发更新
if set.Spec.UpdateStrategy.Type == apps.OnDeleteStatefulSetStrategyType {
return &status, nil
}
// 经过上面那么多条件的过滤和准备，现在要开始对replicas里的合法pod进行检查了
updateMin := 0
if set.Spec.UpdateStrategy.RollingUpdate != nil {
updateMin = int(*set.Spec.UpdateStrategy.RollingUpdate.Partition)
}
// 按pod的序号倒序检查
for target := len(replicas) - 1; target >= updateMin; target-- {
// 如果pod的revision不符合updateRevision，那么删除重建此pod
if getPodRevision(replicas[target]) != updateRevision.Name && !isTerminating(replicas[target]) {
klog.V(2).Infof("StatefulSet %s/%s terminating Pod %s for update",
set.Namespace,
set.Name,
replicas[target].Name)
err := ssc.podControl.DeleteStatefulPod(set, replicas[target])
status.CurrentReplicas--
return &status, err
}
// 合法pod更新过程中，还未到达ready状态的pod，等待它
if !isHealthy(replicas[target]) {
klog.V(4).Infof(
"StatefulSet %s/%s is waiting for Pod %s to update",
set.Namespace,
set.Name,
replicas[target].Name)
return &status, nil
}
}
return &status, nil
}
```
**updateStatefulSet函数总结**
1. 每个循环的周期中，最多操作一个pod
2. 根据sts.spec.replicas对比现有pod的序号，对pod进行划分，一部分划为合法(保留/重建)，一部分划为非法(删除)
3. 对pods进行划分，一部分划入current(old) set阵营，另一部分划入update(new) set阵营
4. 更新过程中，无论是删减、还是新建，都保持pod数量固定，有序地递增、递减
5. 最终保证所有的pod都归属于update revision
## 总结
statefulset 在设计上与 deployment 有许多不同的地方，例如：
- deployment通过rs管理pod，sts通过controllerRevision管理pod；
- deployment curd是无序的，sts强保证有序curd
- sts需要检查存储的匹配
在了解sts管理操作pod方式的基础上来看代码，会有许多的帮助。

9
controller/README.md
Unescape View File

@ -1,11 +1,16 @@
## Controller源码分段阅读导航
- [多实例leader选举](https://github.com/yinwenqin/kubeSourceCodeNote/blob/master/controller/Kubernetes源码学习-Controller-P1-多实例leader选举.md)
- [Controller与informer](https://github.com/yinwenqin/kubeSourceCodeNote/blob/master/controller/Kubernetes源码学习-Controller-P2-Controller与informer.md)
- [Controller分类与Deployment Controller](https://github.com/yinwenqin/kubeSourceCodeNote/blob/master/controller/Kubernetes源码学习-Controller-P3-Controller分类与Deployment Controller.md)
- [ReplicaSet Controller](https://github.com/yinwenqin/kubeSourceCodeNote/blob/master/controller/Kubernetes源码学习-Controller-P4-ReplicaSet Controller.md)
- [StafulSet Controller]
- 待补充
- [StatefulSet Controller](https://github.com/yinwenqin/kubeSourceCodeNote/blob/master/controller/Kubernetes源码学习-Controller-P5-StatefulSet Controller.md)
## 概述

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