k8s client-go原始碼分析 informer原始碼分析(2)-初始化與啟動分析
前面一篇文章對k8s informer做了概要分析，本篇文章將對informer的初始化與啟動進行分析。
informer架構
先來回憶一下informer的架構。
k8s client-go informer主要包括以下部件：
（1）Reflector：Reflector從kube-apiserver中list&watch資源物件，然後呼叫DeltaFIFO的Add/Update/Delete/Replace方法將資源物件及其變化包裝成Delta並將其丟到DeltaFIFO中；
（2）DeltaFIFO：DeltaFIFO中儲存著一個map和一個queue，即map[object key]Deltas以及object key的queue，Deltas為Delta的切片型別，Delta裝有物件及物件的變化型別（Added/Updated/Deleted/Sync） ，Reflector負責DeltaFIFO的輸入，Controller負責處理DeltaFIFO的輸出；
（3）Controller：Controller從DeltaFIFO的queue中pop一個object key出來，並獲取其關聯的 Deltas出來進行處理，遍歷Deltas，根據物件的變化更新Indexer中的本地記憶體快取，並通知Processor，相關物件有變化事件發生；
（4）Processor：Processor根據物件的變化事件型別，呼叫相應的ResourceEventHandler來處理物件的變化；
（5）Indexer：Indexer中有informer維護的指定資源物件的相對於etcd資料的一份本地記憶體快取，可通過該快取獲取資源物件，以減少對apiserver、對etcd的請求壓力；
（6）ResourceEventHandler：使用者根據自身處理邏輯需要，註冊自定義的的ResourceEventHandler，當物件發生變化時，將觸發呼叫對應型別的ResourceEventHandler來做處理。
概述
...
factory := informers.NewSharedInformerFactory(client, 30*time.Second)
podInformer := factory.Core().V1().Pods()
informer := podInformer.Informer()
...
go factory.Start(stopper)
...
if !cache.WaitForCacheSync(stopper, informer.HasSynced) {
runtime.HandleError(fmt.Errorf("Timed out waiting for caches to sync"))
return
}
...
上一節有列舉了informer的使用程式碼，注意看到示例程式碼中的下面這段程式碼，做了informer初始化與啟動，其中包括：
（1）informers.NewSharedInformerFactory：初始化informer factory；
（2）podInformer.Informer：初始化pod informer；
（3）factory.Start：啟動informer factory；
（4）cache.WaitForCacheSync：等待list操作獲取到的物件都同步到informer本地快取Indexer中；
下面也將根據這四部分進行informer的初始化與啟動分析。
基於k8s v1.17.4版本依賴的client-go
1.SharedInformerFactory的初始化
1.1 sharedInformerFactory結構體
先來看下sharedInformerFactory結構體，看下里面有哪些屬性。
看到幾個比較重要的屬性：
（1）client：連線k8s的clientSet；
（2）informers：是個map，可以裝各個物件的informer；
（3）startedInformers：記錄已經啟動的informer；
// staging/src/k8s.io/client-go/informers/factory.go
type sharedInformerFactory struct {
client kubernetes.Interface
namespace string
tweakListOptions internalinterfaces.TweakListOptionsFunc
lock sync.Mutex
defaultResync time.Duration
customResync map[reflect.Type]time.Duration
informers map[reflect.Type]cache.SharedIndexInformer
// startedInformers is used for tracking which informers have been started.
// This allows Start() to be called multiple times safely.
startedInformers map[reflect.Type]bool
}
1.2 NewSharedInformerFactory
NewSharedInformerFactory方法用於初始化informer factory，主要是初始化並返回sharedInformerFactory結構體。
// staging/src/k8s.io/client-go/informers/factory.go
func NewSharedInformerFactory(client kubernetes.Interface, defaultResync time.Duration) SharedInformerFactory {
return NewSharedInformerFactoryWithOptions(client, defaultResync)
}
func NewFilteredSharedInformerFactory(client kubernetes.Interface, defaultResync time.Duration, namespace string, tweakListOptions internalinterfaces.TweakListOptionsFunc) SharedInformerFactory {
return NewSharedInformerFactoryWithOptions(client, defaultResync, WithNamespace(namespace), WithTweakListOptions(tweakListOptions))
}
func NewSharedInformerFactoryWithOptions(client kubernetes.Interface, defaultResync time.Duration, options ...SharedInformerOption) SharedInformerFactory {
factory := &sharedInformerFactory{
client: client,
namespace: v1.NamespaceAll,
defaultResync: defaultResync,
informers: make(map[reflect.Type]cache.SharedIndexInformer),
startedInformers: make(map[reflect.Type]bool),
customResync: make(map[reflect.Type]time.Duration),
}
// Apply all options
for _, opt := range options {
factory = opt(factory)
}
return factory
}
2.物件informer的初始化
上一節有列舉了informer的使用程式碼，注意看到示例程式碼中的下面這段程式碼，這裡利用了工廠方法設計模式，podInformer.Informer()即初始化了sharedInformerFactory中的pod的informer，具體呼叫關係可自行看如下程式碼，比較簡單，這裡不再展開分析。
// 初始化informer factory以及pod informer
factory := informers.NewSharedInformerFactory(client, 30*time.Second)
podInformer := factory.Core().V1().Pods()
informer := podInformer.Informer()
2.1 podInformer.Informer
Informer方法中呼叫了f.factory.InformerFor方法來做pod informer的初始化。
// k8s.io/client-go/informers/core/v1/pod.go
func (f *podInformer) Informer() cache.SharedIndexInformer {
return f.factory.InformerFor(&corev1.Pod{}, f.defaultInformer)
}
2.2 f.factory.InformerFor
Informer方法中呼叫了f.factory.InformerFor方法來做pod informer的初始化，並傳入f.defaultInformer作為newFunc，而在f.factory.InformerFor方法中，呼叫newFunc來初始化informer。
這裡也可以看到，其實informer初始化後會儲存進map f.informers[informerType]中，即儲存進sharedInformerFactory結構體的informers屬性中，方便共享使用。
// staging/src/k8s.io/client-go/informers/factory.go
func (f *sharedInformerFactory) InformerFor(obj runtime.Object, newFunc internalinterfaces.NewInformerFunc) cache.SharedIndexInformer {
f.lock.Lock()
defer f.lock.Unlock()
informerType := reflect.TypeOf(obj)
informer, exists := f.informers[informerType]
if exists {
return informer
}
resyncPeriod, exists := f.customResync[informerType]
if !exists {
resyncPeriod = f.defaultResync
}
informer = newFunc(f.client, resyncPeriod)
f.informers[informerType] = informer
return informer
}
2.3 newFunc/f.defaultInformer
defaultInformer方法中，呼叫了NewFilteredPodInformer方法來初始化pod informer，最終初始化並返回sharedIndexInformer結構體。
// k8s.io/client-go/informers/core/v1/pod.go
func (f *podInformer) defaultInformer(client kubernetes.Interface, resyncPeriod time.Duration) cache.SharedIndexInformer {
return NewFilteredPodInformer(client, f.namespace, resyncPeriod, cache.Indexers{cache.NamespaceIndex: cache.MetaNamespaceIndexFunc}, f.tweakListOptions)
}
func NewFilteredPodInformer(client kubernetes.Interface, namespace string, resyncPeriod time.Duration, indexers cache.Indexers, tweakListOptions internalinterfaces.TweakListOptionsFunc) cache.SharedIndexInformer {
return cache.NewSharedIndexInformer(
&cache.ListWatch{
ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
if tweakListOptions != nil {
tweakListOptions(&options)
}
return client.CoreV1().Pods(namespace).List(options)
},
WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
if tweakListOptions != nil {
tweakListOptions(&options)
}
return client.CoreV1().Pods(namespace).Watch(options)
},
},
&corev1.Pod{},
resyncPeriod,
indexers,
)
}
func NewSharedIndexInformer(lw ListerWatcher, objType runtime.Object, defaultEventHandlerResyncPeriod time.Duration, indexers Indexers) SharedIndexInformer {
realClock := &clock.RealClock{}
sharedIndexInformer := &sharedIndexInformer{
processor: &sharedProcessor{clock: realClock},
indexer: NewIndexer(DeletionHandlingMetaNamespaceKeyFunc, indexers),
listerWatcher: lw,
objectType: objType,
resyncCheckPeriod: defaultEventHandlerResyncPeriod,
defaultEventHandlerResyncPeriod: defaultEventHandlerResyncPeriod,
cacheMutationDetector: NewCacheMutationDetector(fmt.Sprintf("%T", objType)),
clock: realClock,
}
return sharedIndexInformer
}
2.4 sharedIndexInformer結構體
sharedIndexInformer結構體中重點看到以下幾個屬性：
（1）indexer：對應著informer中的部件Indexer，Indexer中有informer維護的指定資源物件的相對於etcd資料的一份本地記憶體快取，可通過該快取獲取資源物件，以減少對apiserver、對etcd的請求壓力；
（2）controller：對應著informer中的部件Controller，Controller從DeltaFIFO中pop Deltas出來處理，根據物件的變化更新Indexer中的本地記憶體快取，並通知Processor，相關物件有變化事件發生；
（3）processor：對應著informer中的部件Processor，Processor根據物件的變化事件型別，呼叫相應的ResourceEventHandler來處理物件的變化；
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
type sharedIndexInformer struct {
indexer Indexer
controller Controller
processor *sharedProcessor
cacheMutationDetector CacheMutationDetector
// This block is tracked to handle late initialization of the controller
listerWatcher ListerWatcher
objectType runtime.Object
// resyncCheckPeriod is how often we want the reflector's resync timer to fire so it can call
// shouldResync to check if any of our listeners need a resync.
resyncCheckPeriod time.Duration
// defaultEventHandlerResyncPeriod is the default resync period for any handlers added via
// AddEventHandler (i.e. they don't specify one and just want to use the shared informer's default
// value).
defaultEventHandlerResyncPeriod time.Duration
// clock allows for testability
clock clock.Clock
started, stopped bool
startedLock sync.Mutex
// blockDeltas gives a way to stop all event distribution so that a late event handler
// can safely join the shared informer.
blockDeltas sync.Mutex
}
Indexer介面與cache結構體
cache結構體為Indexer介面的實現；
// staging/src/k8s.io/client-go/tools/cache/store.go
type cache struct {
cacheStorage ThreadSafeStore
keyFunc KeyFunc
}
threadSafeMap struct是ThreadSafeStore介面的一個實現，其最重要的一個屬性便是items了，items是用map構建的鍵值對，資源物件都存在items這個map中，key根據資源物件來算出，value為資源物件本身，這裡的items即為informer的本地快取了，而indexers與indices屬性則與索引功能有關。
// staging/src/k8s.io/client-go/tools/cache/thread_safe_store.go
type threadSafeMap struct {
lock sync.RWMutex
items map[string]interface{}
// indexers maps a name to an IndexFunc
indexers Indexers
// indices maps a name to an Index
indices Indices
}
關於Indexer的詳細分析會在後續有專門的文章做分析，這裡不展開分析；
controller結構體
而controller結構體則包含了informer中的主要部件Reflector以及DeltaFIFO；
（1）Reflector：Reflector從kube-apiserver中list&watch資源物件，然後將物件的變化包裝成Delta並將其丟到DeltaFIFO中；
（2）DeltaFIFO：DeltaFIFO儲存著map[object key]Deltas以及object key的queue，Delta裝有物件及物件的變化型別 ，Reflector負責DeltaFIFO的輸入，Controller負責處理DeltaFIFO的輸出；
// staging/src/k8s.io/client-go/tools/cache/controller.go
type controller struct {
config Config
reflector *Reflector
reflectorMutex sync.RWMutex
clock clock.Clock
}
type Config struct {
// The queue for your objects; either a FIFO or
// a DeltaFIFO. Your Process() function should accept
// the output of this Queue's Pop() method.
Queue
...
}
3.啟動sharedInformerFactory
sharedInformerFactory.Start為informer factory的啟動方法，其主要邏輯為迴圈遍歷informers，然後跑goroutine呼叫informer.Run來啟動sharedInformerFactory中儲存的各個informer。
// staging/src/k8s.io/client-go/informers/factory.go
func (f *sharedInformerFactory) Start(stopCh <-chan struct{}) {
f.lock.Lock()
defer f.lock.Unlock()
for informerType, informer := range f.informers {
if !f.startedInformers[informerType] {
go informer.Run(stopCh)
f.startedInformers[informerType] = true
}
}
}
sharedIndexInformer.Run
sharedIndexInformer.Run用於啟動informer，主要邏輯為：
（1）呼叫NewDeltaFIFO，初始化DeltaFIFO；
（2）構建Config結構體，這裡留意下Process屬性，賦值了s.HandleDeltas，後面會分析到該方法；
（3）呼叫New，利用Config結構體來初始化controller；
（4）呼叫s.processor.run，啟動processor；
（5）呼叫s.controller.Run，啟動controller；
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (s *sharedIndexInformer) Run(stopCh <-chan struct{}) {
defer utilruntime.HandleCrash()
// 初始化DeltaFIFO
fifo := NewDeltaFIFO(MetaNamespaceKeyFunc, s.indexer)
// 構建Config結構體
cfg := &Config{
Queue: fifo,
ListerWatcher: s.listerWatcher,
ObjectType: s.objectType,
FullResyncPeriod: s.resyncCheckPeriod,
RetryOnError: false,
ShouldResync: s.processor.shouldResync,
Process: s.HandleDeltas,
}
func() {
s.startedLock.Lock()
defer s.startedLock.Unlock()
// 初始化controller
s.controller = New(cfg)
s.controller.(*controller).clock = s.clock
s.started = true
}()
// Separate stop channel because Processor should be stopped strictly after controller
processorStopCh := make(chan struct{})
var wg wait.Group
defer wg.Wait() // Wait for Processor to stop
defer close(processorStopCh) // Tell Processor to stop
wg.StartWithChannel(processorStopCh, s.cacheMutationDetector.Run)
// 啟動processor
wg.StartWithChannel(processorStopCh, s.processor.run)
defer func() {
s.startedLock.Lock()
defer s.startedLock.Unlock()
s.stopped = true // Don't want any new listeners
}()
// 啟動controller
s.controller.Run(stopCh)
}
3.1 New
New函式初始化了controller並return。
// staging/src/k8s.io/client-go/tools/cache/controller.go
func New(c *Config) Controller {
ctlr := &controller{
config: *c,
clock: &clock.RealClock{},
}
return ctlr
}
3.2 s.processor.run
s.processor.run啟動了processor，其中注意到listener.run與listener.pop兩個核心方法即可，暫時沒有用到，等下面用到他們的時候再做分析。
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (p *sharedProcessor) run(stopCh <-chan struct{}) {
func() {
p.listenersLock.RLock()
defer p.listenersLock.RUnlock()
for _, listener := range p.listeners {
p.wg.Start(listener.run)
p.wg.Start(listener.pop)
}
p.listenersStarted = true
}()
<-stopCh
p.listenersLock.RLock()
defer p.listenersLock.RUnlock()
for _, listener := range p.listeners {
close(listener.addCh) // Tell .pop() to stop. .pop() will tell .run() to stop
}
p.wg.Wait() // Wait for all .pop() and .run() to stop
}
3.3 controller.Run
controller.Run為controller的啟動方法，這裡主要看到幾個點：
（1）呼叫NewReflector，初始化Reflector；
（2）呼叫r.Run，實際上是呼叫了Reflector的啟動方法來啟動Reflector；
（3）呼叫c.processLoop，開始controller的核心處理；
// k8s.io/client-go/tools/cache/controller.go
func (c *controller) Run(stopCh <-chan struct{}) {
defer utilruntime.HandleCrash()
go func() {
<-stopCh
c.config.Queue.Close()
}()
r := NewReflector(
c.config.ListerWatcher,
c.config.ObjectType,
c.config.Queue,
c.config.FullResyncPeriod,
)
r.ShouldResync = c.config.ShouldResync
r.clock = c.clock
c.reflectorMutex.Lock()
c.reflector = r
c.reflectorMutex.Unlock()
var wg wait.Group
defer wg.Wait()
wg.StartWithChannel(stopCh, r.Run)
wait.Until(c.processLoop, time.Second, stopCh)
}
3.3.1 Reflector結構體
先來看到Reflector結構體，這裡重點看到以下屬性：
（1）expectedType：放到Store中（即DeltaFIFO中）的物件型別；
（2）store：store會賦值為DeltaFIFO，具體可以看之前的informer初始化與啟動分析即可得知，這裡不再展開分析；
（3）listerWatcher：存放list方法和watch方法的ListerWatcher interface實現；
// k8s.io/client-go/tools/cache/reflector.go
type Reflector struct {
...
expectedType reflect.Type
store Store
listerWatcher ListerWatcher
...
}
3.3.2 r.Run/Reflector.Run
Reflector.Run方法中啟動了Reflector，而Reflector的核心處理邏輯為從kube-apiserver處做list&watch操作，然後將得到的物件封裝儲存進DeltaFIFO中。
// staging/src/k8s.io/client-go/tools/cache/reflector.go
func (r *Reflector) Run(stopCh <-chan struct{}) {
klog.V(3).Infof("Starting reflector %v (%s) from %s", r.expectedTypeName, r.resyncPeriod, r.name)
wait.Until(func() {
if err := r.ListAndWatch(stopCh); err != nil {
utilruntime.HandleError(err)
}
}, r.period, stopCh)
}
3.3.3 controller.processLoop
controller的核心處理方法processLoop中，最重要的邏輯是迴圈呼叫c.config.Queue.Pop將DeltaFIFO中的隊頭元素給pop出來，然後呼叫c.config.Process方法來做處理，當處理出錯時，再呼叫c.config.Queue.AddIfNotPresent將物件重新加入到DeltaFIFO中去。
// k8s.io/client-go/tools/cache/controller.go
func (c *controller) processLoop() {
for {
obj, err := c.config.Queue.Pop(PopProcessFunc(c.config.Process))
if err != nil {
if err == ErrFIFOClosed {
return
}
if c.config.RetryOnError {
// This is the safe way to re-enqueue.
c.config.Queue.AddIfNotPresent(obj)
}
}
}
}
3.3.4 c.config.Process/sharedIndexInformer.HandleDeltas
根據前面sharedIndexInformer.Run方法的分析中可以得知，c.config.Process其實就是sharedIndexInformer.HandleDeltas。
HandleDeltas方法中，將從DeltaFIFO中pop出來的物件以及型別，相應的在indexer中做新增、更新、刪除操作，並呼叫s.processor.distribute通知自定義的ResourceEventHandler。
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (s *sharedIndexInformer) HandleDeltas(obj interface{}) error {
s.blockDeltas.Lock()
defer s.blockDeltas.Unlock()
// from oldest to newest
for _, d := range obj.(Deltas) {
switch d.Type {
case Sync, Added, Updated:
isSync := d.Type == Sync
s.cacheMutationDetector.AddObject(d.Object)
if old, exists, err := s.indexer.Get(d.Object); err == nil && exists {
if err := s.indexer.Update(d.Object); err != nil {
return err
}
s.processor.distribute(updateNotification{oldObj: old, newObj: d.Object}, isSync)
} else {
if err := s.indexer.Add(d.Object); err != nil {
return err
}
s.processor.distribute(addNotification{newObj: d.Object}, isSync)
}
case Deleted:
if err := s.indexer.Delete(d.Object); err != nil {
return err
}
s.processor.distribute(deleteNotification{oldObj: d.Object}, false)
}
}
return nil
}
怎麼通知到自定義的ResourceEventHandler呢？繼續往下看。
3.3.5 sharedIndexInformer.processor.distribute
可以看到distribute方法最終是將構造好的addNotification、updateNotification、deleteNotification物件寫入到p.addCh中。
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (p *sharedProcessor) distribute(obj interface{}, sync bool) {
p.listenersLock.RLock()
defer p.listenersLock.RUnlock()
if sync {
for _, listener := range p.syncingListeners {
listener.add(obj)
}
} else {
for _, listener := range p.listeners {
listener.add(obj)
}
}
}
func (p *processorListener) add(notification interface{}) {
p.addCh <- notification
}
到這裡，processor中的listener.pop以及listener.run方法終於派上了用場，繼續往下看。
3.3.6 listener.pop
分析processorListener的pop方法可以得知，其邏輯實際上就是將p.addCh中的物件給拿出來，然後丟進了p.nextCh中。那麼誰來處理p.nextCh呢？繼續往下看。
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (p *processorListener) pop() {
defer utilruntime.HandleCrash()
defer close(p.nextCh) // Tell .run() to stop
var nextCh chan<- interface{}
var notification interface{}
for {
select {
case nextCh <- notification:
// Notification dispatched
var ok bool
notification, ok = p.pendingNotifications.ReadOne()
if !ok { // Nothing to pop
nextCh = nil // Disable this select case
}
case notificationToAdd, ok := <-p.addCh:
if !ok {
return
}
if notification == nil { // No notification to pop (and pendingNotifications is empty)
// Optimize the case - skip adding to pendingNotifications
notification = notificationToAdd
nextCh = p.nextCh
} else { // There is already a notification waiting to be dispatched
p.pendingNotifications.WriteOne(notificationToAdd)
}
}
}
}
3.3.7 listener.run
在processorListener的run方法中，將迴圈讀取p.nextCh，判斷物件型別，是updateNotification則呼叫p.handler.OnUpdate方法，是addNotification則呼叫p.handler.OnAdd方法，是deleteNotification則呼叫p.handler.OnDelete方法做處理。
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (p *processorListener) run() {
// this call blocks until the channel is closed. When a panic happens during the notification
// we will catch it, **the offending item will be skipped!**, and after a short delay (one second)
// the next notification will be attempted. This is usually better than the alternative of never
// delivering again.
stopCh := make(chan struct{})
wait.Until(func() {
// this gives us a few quick retries before a long pause and then a few more quick retries
err := wait.ExponentialBackoff(retry.DefaultRetry, func() (bool, error) {
for next := range p.nextCh {
switch notification := next.(type) {
case updateNotification:
p.handler.OnUpdate(notification.oldObj, notification.newObj)
case addNotification:
p.handler.OnAdd(notification.newObj)
case deleteNotification:
p.handler.OnDelete(notification.oldObj)
default:
utilruntime.HandleError(fmt.Errorf("unrecognized notification: %T", next))
}
}
// the only way to get here is if the p.nextCh is empty and closed
return true, nil
})
// the only way to get here is if the p.nextCh is empty and closed
if err == nil {
close(stopCh)
}
}, 1*time.Minute, stopCh)
}
而p.handler.OnUpdate、p.handler.OnAdd、p.handler.OnDelete方法實際上就是自定義的的ResourceEventHandlerFuncs了。
informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
AddFunc: onAdd,
UpdateFunc: onUpdate,
DeleteFunc: onDelete,
})
// staging/src/k8s.io/client-go/tools/cache/controller.go
type ResourceEventHandlerFuncs struct {
AddFunc func(obj interface{})
UpdateFunc func(oldObj, newObj interface{})
DeleteFunc func(obj interface{})
}
func (r ResourceEventHandlerFuncs) OnAdd(obj interface{}) {
if r.AddFunc != nil {
r.AddFunc(obj)
}
}
func (r ResourceEventHandlerFuncs) OnUpdate(oldObj, newObj interface{}) {
if r.UpdateFunc != nil {
r.UpdateFunc(oldObj, newObj)
}
}
func (r ResourceEventHandlerFuncs) OnDelete(obj interface{}) {
if r.DeleteFunc != nil {
r.DeleteFunc(obj)
}
}
4.cache.WaitForCacheSync(stopper, informer.HasSynced)
可以看出在cache.WaitForCacheSync方法中，實際上是呼叫方法入參cacheSyncs ...InformerSynced來判斷cache是否同步完成（即呼叫informer.HasSynced方法），而這裡說的cache同步完成，意思是等待informer從kube-apiserver同步資源完成，即informer的list操作獲取的物件都存入到informer中的indexer本地快取中；
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func WaitForCacheSync(stopCh <-chan struct{}, cacheSyncs ...InformerSynced) bool {
err := wait.PollImmediateUntil(syncedPollPeriod,
func() (bool, error) {
for _, syncFunc := range cacheSyncs {
if !syncFunc() {
return false, nil
}
}
return true, nil
},
stopCh)
if err != nil {
klog.V(2).Infof("stop requested")
return false
}
klog.V(4).Infof("caches populated")
return true
}
4.1 informer.HasSynced
HasSynced方法實際上是呼叫了sharedIndexInformer.controller.HasSynced方法；
// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (s *sharedIndexInformer) HasSynced() bool {
s.startedLock.Lock()
defer s.startedLock.Unlock()
if s.controller == nil {
return false
}
return s.controller.HasSynced()
}
s.controller.HasSynced
這裡的c.config.Queue.HasSynced()方法，實際上是指DeltaFIFO的HasSynced方法，會在DeltaFIFO的分析中再詳細分析，這裡只需要知道當informer的list操作獲取的物件都存入到informer中的indexer本地快取中則返回true即可；
// staging/src/k8s.io/client-go/tools/cache/controller.go
func (c *controller) HasSynced() bool {
return c.config.Queue.HasSynced()
}
4.2 sharedInformerFactory.WaitForCacheSync
可以順帶看下sharedInformerFactory.WaitForCacheSync方法，其實際上是遍歷factory中的所有informer，呼叫cache.WaitForCacheSync，然後傳入每個informer的HasSynced方法作為入參；
// staging/src/k8s.io/client-go/informers/factory.go
func (f *sharedInformerFactory) WaitForCacheSync(stopCh <-chan struct{}) map[reflect.Type]bool {
informers := func() map[reflect.Type]cache.SharedIndexInformer {
f.lock.Lock()
defer f.lock.Unlock()
informers := map[reflect.Type]cache.SharedIndexInformer{}
for informerType, informer := range f.informers {
if f.startedInformers[informerType] {
informers[informerType] = informer
}
}
return informers
}()
res := map[reflect.Type]bool{}
for informType, informer := range informers {
res[informType] = cache.WaitForCacheSync(stopCh, informer.HasSynced)
}
return res
}
至此，整個informer的初始化與啟動的分析就結束了，後面會對informer中的各個核心部件進行詳細分析，敬請期待。
總結
下面用兩張圖片總結一下informer的初始化與啟動；
informer初始化
informer啟動
