From 6080042e26473a2a818de647d177603772ff89c5 Mon Sep 17 00:00:00 2001
From: dongming <dongming@dongming-pc>
Date: Tue, 13 Dec 2022 16:23:04 +0800
Subject: [PATCH] l-20

---
 .../k8s.io/client-go/tools/cache/reflector.go | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/vendor/k8s.io/client-go/tools/cache/reflector.go b/vendor/k8s.io/client-go/tools/cache/reflector.go
index d2d21ca..4e4be02 100644
--- a/vendor/k8s.io/client-go/tools/cache/reflector.go
+++ b/vendor/k8s.io/client-go/tools/cache/reflector.go
@@ -317,8 +317,11 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 	}()
 
 	// 执行 watch 操作
+
+	// 创建 retry 对象，来控制下面的循环行为
 	retry := NewRetryWithDeadline(r.MaxInternalErrorRetryDuration, time.Minute, apierrors.IsInternalError, r.clock)
 	for {
+		// 控制循环退出的逻辑，只有发送stop信号，才能退出 *是说仅仅这里的控制*
 		// give the stopCh a chance to stop the loop, even in case of continue statements further down on errors
 		select {
 		case <-stopCh:
@@ -340,6 +343,8 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 
 		// start the clock before sending the request, since some proxies won't flush headers until after the first watch event is sent
 		start := r.clock.Now()
+
+		// 执行外部传进来对象的 watch 操作。返回的是一个对象，这个对象可以被看作一个进程，他会一直watch着变化的事件，供后续可以不断从中读出事件
 		w, err := r.listerWatcher.Watch(options)
 		if err != nil {
 			// If this is "connection refused" error, it means that most likely apiserver is not responsive.
@@ -348,12 +353,14 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 			// If that's the case begin exponentially backing off and resend watch request.
 			// Do the same for "429" errors.
 			if utilnet.IsConnectionRefused(err) || apierrors.IsTooManyRequests(err) {
+				// 如果时上面的两种错误之一，则会重新进入循环，但是要等待一定的时间
 				<-r.initConnBackoffManager.Backoff().C()
 				continue
 			}
 			return err
 		}
 
+		// 处理watch对象的函数，主要是不断的读出event
 		err = watchHandler(start, w, r.store, r.expectedType, r.expectedGVK, r.name, r.expectedTypeName, r.setLastSyncResourceVersion, r.clock, resyncerrc, stopCh)
 		retry.After(err)
 		if err != nil {
@@ -536,34 +543,48 @@ loop:
 	for {
 		select {
 		case <-stopCh:
+			// 如果是收到结束信号，返回的这个错误，在外面调用方，不会判断其他错误，直接退出
 			return errorStopRequested
 		case err := <-errc:
 			return err
 		case event, ok := <-w.ResultChan():
+			// 获取 watch 对象中的事件
+			// 如果 ok 时 false， 则时应为 watch 被关闭，而不是读出了event
 			if !ok {
 				break loop
 			}
+
+			// 这里时说 event 的错误类型时 watch.Error，并不是获取event的时候出错
 			if event.Type == watch.Error {
 				return apierrors.FromObject(event.Object)
 			}
+
+			// 期望的类型和 event的类型 是否相同，不同的时候会产生错误，并跳过后面的执行，开始下次循环
 			if expectedType != nil {
 				if e, a := expectedType, reflect.TypeOf(event.Object); e != a {
 					utilruntime.HandleError(fmt.Errorf("%s: expected type %v, but watch event object had type %v", name, e, a))
 					continue
 				}
 			}
+
+			// 期望的 GVK 和 event的 GVK 是否相同，不同的时候会产生错误，并跳过后面的执行，开始下次循环
 			if expectedGVK != nil {
 				if e, a := *expectedGVK, event.Object.GetObjectKind().GroupVersionKind(); e != a {
 					utilruntime.HandleError(fmt.Errorf("%s: expected gvk %v, but watch event object had gvk %v", name, e, a))
 					continue
 				}
 			}
+
+			// 备份 resourceVersion
+			// 创建一个提取器
 			meta, err := meta.Accessor(event.Object)
 			if err != nil {
 				utilruntime.HandleError(fmt.Errorf("%s: unable to understand watch event %#v", name, event))
 				continue
 			}
 			resourceVersion := meta.GetResourceVersion()
+
+			// 根据不同的事件类型做不同的处理
 			switch event.Type {
 			case watch.Added:
 				err := store.Add(event.Object)
@@ -596,6 +617,8 @@ loop:
 		}
 	}
 
+	// 到这里 watch 操作就结束了
+
 	watchDuration := clock.Since(start)
 	if watchDuration < 1*time.Second && eventCount == 0 {
 		return fmt.Errorf("very short watch: %s: Unexpected watch close - watch lasted less than a second and no items received", name)