前言

最近做项目，还是K8S的插件监听器（理论上插件都是通过API-server通信），官方的不同写法居然都能出现争议，争议点就是对API-Server的请求的耗时，说是会影响API-Server。实际上通过源码分析两着有差别，但是差别不大，对API-Server的影响几乎一样。

老式写法

package main

import (
	"controller/control"
	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/fields"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/util/workqueue"
	"k8s.io/klog/v2"
)

func main() {

	// 读取构建 config
	config, err := clientcmd.BuildConfigFromFlags("", "xxx/config")
	if err != nil {
		klog.Fatal(err)
	}

	// 创建 k8s client
	clientSet, err := kubernetes.NewForConfig(config)
	if err != nil {
		klog.Fatal(err)
	}

	// 指定 ListWatcher 在所有namespace下监听 pod 资源
	podListWatcher := cache.NewListWatchFromClient(clientSet.CoreV1().RESTClient(), "pods", v1.NamespaceAll, fields.Everything())

	// 创建 workqueue
	queue := workqueue.NewRateLimitingQueue(workqueue.DefaultControllerRateLimiter())

	// 创建 indexer 和 informer
	indexer, informer := cache.NewIndexerInformer(podListWatcher, &v1.Pod{}, 0, cache.ResourceEventHandlerFuncs{
		// 当有 pod 创建时，根据 Delta queue 弹出的 object 生成对应的Key，并加入到 workqueue中。此处可以根据Object的一些属性，进行过滤
		AddFunc: func(obj interface{}) {
			key, err := cache.MetaNamespaceKeyFunc(obj)
			if err == nil {
				queue.Add(key)
			}
		},
		UpdateFunc: func(obj, newObj interface{}) {
			key, err := cache.MetaNamespaceKeyFunc(newObj)
			if err == nil {
				queue.Add(key)
			}
		},
		// pod 删除操作
		DeleteFunc: func(obj interface{}) {
			// DeletionHandlingMetaNamespaceKeyFunc 会在生成key 之前检查。因为资源删除后有可能会进行重建等操作，监听时错过了删除信息，从而导致该条记录是陈旧的。
			key, err := cache.DeletionHandlingMetaNamespaceKeyFunc(obj)
			if err == nil {
				queue.Add(key)
			}
		},
	}, cache.Indexers{})

	controller := control.NewController(queue, indexer, informer)

	stop := make(chan struct{})

	defer close(stop)
	// 启动 control
	go controller.Run(1, stop)

	select {}
}

然后写个Controller代码

package control

import (
	"fmt"
	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/util/workqueue"
	"k8s.io/klog/v2"
	"time"
)

type Controller struct {
	indexer  cache.Indexer                   // Indexer 的引用
	queue    workqueue.RateLimitingInterface //workqueue 的引用
	informer cache.Controller                // Informer 的引用
}

func NewController(queue workqueue.RateLimitingInterface, indexer cache.Indexer, informer cache.Controller) *Controller {
	return &Controller{
		indexer:  indexer,
		queue:    queue,
		informer: informer,
	}
}

func (c *Controller) Run(threadiness int, stopCh chan struct{}) {
	defer runtime.HandleCrash()

	defer c.queue.ShutDown()

	klog.Info("Starting pod control")

	go c.informer.Run(stopCh) // 启动 informer

	if !cache.WaitForCacheSync(stopCh, c.informer.HasSynced) {
		runtime.HandleError(fmt.Errorf("time out waitng for caches to sync"))
		return
	}

	// 启动多个 worker 处理 workqueue 中的对象
	for i := 0; i < threadiness; i++ {
		go wait.Until(c.runWorker, time.Second, stopCh)
	}

	<-stopCh
	klog.Info("Stopping Pod control")
}

func (c *Controller) runWorker() {
	// 启动无限循环，接收并处理消息
	for c.processNextItem() {

	}
}

// 从 workqueue 中获取对象，并打印信息。
func (c *Controller) processNextItem() bool {
	key, shutdown := c.queue.Get()
	// 退出
	if shutdown {
		return false
	}

	// 标记此key已经处理
	defer c.queue.Done(key)

	// 将key对应的 object 的信息进行打印
	err := c.syncToStdout(key.(string))

	c.handleError(err, key)
	return true
}

// 获取 key 对应的 object，并打印相关信息
func (c *Controller) syncToStdout(key string) error {
	obj, exists, err := c.indexer.GetByKey(key)
	if err != nil {
		klog.Errorf("Fetching object with key %s from store failed with %v", key, err)
		return err
	}
	if !exists {
		fmt.Printf("Pod %s does not exist\n", obj.(*v1.Pod).GetName())
	} else {
		fmt.Printf("Sync/Add/Update for Pod %s\n", obj.(*v1.Pod).GetName())
	}
	return nil
}

func (c *Controller) handleError(err error, key interface{}) {

}

这总写法的好处是自己处理各个环节，Informer和indexer，那个queue仅仅是队列，从cache缓存取数据用的，实际看看创建过程

创建lw的过程

cache.NewListWatchFromClient

// NewListWatchFromClient creates a new ListWatch from the specified client, resource, namespace and field selector.
func NewListWatchFromClient(c Getter, resource string, namespace string, fieldSelector fields.Selector) *ListWatch {
	optionsModifier := func(options *metav1.ListOptions) {
		options.FieldSelector = fieldSelector.String()
	}
	return NewFilteredListWatchFromClient(c, resource, namespace, optionsModifier)
}

// NewFilteredListWatchFromClient creates a new ListWatch from the specified client, resource, namespace, and option modifier.
// Option modifier is a function takes a ListOptions and modifies the consumed ListOptions. Provide customized modifier function
// to apply modification to ListOptions with a field selector, a label selector, or any other desired options.
func NewFilteredListWatchFromClient(c Getter, resource string, namespace string, optionsModifier func(options *metav1.ListOptions)) *ListWatch {
	listFunc := func(options metav1.ListOptions) (runtime.Object, error) {
		optionsModifier(&options)
		return c.Get().
			Namespace(namespace).
			Resource(resource).
			VersionedParams(&options, metav1.ParameterCodec).
			Do(context.TODO()).
			Get()
	}
	watchFunc := func(options metav1.ListOptions) (watch.Interface, error) {
		options.Watch = true
		optionsModifier(&options)
		return c.Get().
			Namespace(namespace).
			Resource(resource).
			VersionedParams(&options, metav1.ParameterCodec).
			Watch(context.TODO())
	}
	return &ListWatch{ListFunc: listFunc, WatchFunc: watchFunc}
}

ListAndWatch方法，函数指针，关键是List和Watch的函数，跟新的写法有些许区别

创建Informer

此处默认使用DeletionHandlingMetaNamespaceKeyFunc函数创建key

func NewIndexerInformer(
	lw ListerWatcher,
	objType runtime.Object,
	resyncPeriod time.Duration,
	h ResourceEventHandler,
	indexers Indexers,
) (Indexer, Controller) {
	// This will hold the client state, as we know it.
	clientState := NewIndexer(DeletionHandlingMetaNamespaceKeyFunc, indexers)

	return clientState, newInformer(lw, objType, resyncPeriod, h, clientState, nil)
}

func newInformer(
	lw ListerWatcher,
	objType runtime.Object,
	resyncPeriod time.Duration,
	h ResourceEventHandler,
	clientState Store,
	transformer TransformFunc,
) Controller {
	// This will hold incoming changes. Note how we pass clientState in as a
	// KeyLister, that way resync operations will result in the correct set
	// of update/delete deltas.
	fifo := NewDeltaFIFOWithOptions(DeltaFIFOOptions{
		KnownObjects:          clientState,
		EmitDeltaTypeReplaced: true,
	})

	cfg := &Config{
		Queue:            fifo,
		ListerWatcher:    lw,
		ObjectType:       objType,
		FullResyncPeriod: resyncPeriod,
		RetryOnError:     false,

		Process: func(obj interface{}) error {
			if deltas, ok := obj.(Deltas); ok {
				return processDeltas(h, clientState, transformer, deltas)
			}
			return errors.New("object given as Process argument is not Deltas")
		},
	}
	return New(cfg)
}

func New(c *Config) Controller {
	ctlr := &controller{
		config: *c,
		clock:  &clock.RealClock{},
	}
	return ctlr
}

这里注意，消费delta队列的过程 ，这里是没有加锁的，即Process函数指针

另外实际上还是创建controller内置结构体，也是client-go创建的。

 

新式写法

    config, err := clientcmd.BuildConfigFromFlags("", "~/.kube/config")//注意路径
	if err != nil {
		log.Fatal(err)
	}
    //这2行是抓包的时候使用，日常是不需要的
	config.TLSClientConfig.CAData = nil
	config.TLSClientConfig.Insecure = true
 
	clientSet, err := kubernetes.NewForConfig(config)
	if err != nil {
		log.Fatal(err)
	}
 
    //这里可以调一些参数，defaultResync很关键
	factory := informers.NewSharedInformerFactoryWithOptions(clientSet, 0, informers.WithNamespace("default"))
	informer := factory.Core().V1().Pods().Informer()//获取pod的informer，实际上使用client-go的api很多informer都创建了，直接拿过来用，避免使用的时候重复创建
	informer.AddEventHandler(xxx) //事件处理，是一个回调hook
 
	stopper := make(chan struct{}, 1)
	go informer.Run(stopper)
	log.Println("----- list and watch pod starting...")
 
	sigs := make(chan os.Signal, 1)
	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
	<-sigs
 
	close(stopper)
	log.Println("main stopped...")

实际上就是很多过程封装了，比如创建Controller的过程

lw的创建过程

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(context.TODO(), options)
			},
			WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
				if tweakListOptions != nil {
					tweakListOptions(&options)
				}
				return client.CoreV1().Pods(namespace).Watch(context.TODO(), options)
			},
		},
		&corev1.Pod{},
		resyncPeriod,
		indexers,
	)
}

实际上实现是有pod实现的，List最后取结果略有区别

// List takes label and field selectors, and returns the list of Pods that match those selectors.
func (c *pods) List(ctx context.Context, opts metav1.ListOptions) (result *v1.PodList, err error) {
	var timeout time.Duration
	if opts.TimeoutSeconds != nil {
		timeout = time.Duration(*opts.TimeoutSeconds) * time.Second
	}
	result = &v1.PodList{}
	err = c.client.Get().
		Namespace(c.ns).
		Resource("pods").
		VersionedParams(&opts, scheme.ParameterCodec).
		Timeout(timeout).
		Do(ctx).
		Into(result)
	return
}

// Watch returns a watch.Interface that watches the requested pods.
func (c *pods) Watch(ctx context.Context, opts metav1.ListOptions) (watch.Interface, error) {
	var timeout time.Duration
	if opts.TimeoutSeconds != nil {
		timeout = time.Duration(*opts.TimeoutSeconds) * time.Second
	}
	opts.Watch = true
	return c.client.Get().
		Namespace(c.ns).
		Resource("pods").
		VersionedParams(&opts, scheme.ParameterCodec).
		Timeout(timeout).
		Watch(ctx)
}

最关键的一点，超时，老式写法是没有超时设置的，超时的重要性不言而喻，推荐使用新写法

indexer的创建

默认使用MetaNamespaceIndexFunc函数创建key

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)
}

创建Informer的同时创建indexer

func NewSharedIndexInformer(lw ListerWatcher, exampleObject runtime.Object, defaultEventHandlerResyncPeriod time.Duration, indexers Indexers) SharedIndexInformer {
	realClock := &clock.RealClock{}
	sharedIndexInformer := &sharedIndexInformer{
		processor:                       &sharedProcessor{clock: realClock},
		indexer:                         NewIndexer(DeletionHandlingMetaNamespaceKeyFunc, indexers),
		listerWatcher:                   lw,
		objectType:                      exampleObject,
		resyncCheckPeriod:               defaultEventHandlerResyncPeriod,
		defaultEventHandlerResyncPeriod: defaultEventHandlerResyncPeriod,
		cacheMutationDetector:           NewCacheMutationDetector(fmt.Sprintf("%T", exampleObject)),
		clock:                           realClock,
	}
	return sharedIndexInformer
}

// NewIndexer returns an Indexer implemented simply with a map and a lock.
func NewIndexer(keyFunc KeyFunc, indexers Indexers) Indexer {
	return &cache{
		cacheStorage: NewThreadSafeStore(indexers, Indices{}),
		keyFunc:      keyFunc,
	}
}

除了创建key的函数不同，其他一模一样 ，但是解析delta队列确加了锁

func (s *sharedIndexInformer) HandleDeltas(obj interface{}) error {
	s.blockDeltas.Lock()
	defer s.blockDeltas.Unlock()

	if deltas, ok := obj.(Deltas); ok {
		return processDeltas(s, s.indexer, s.transform, deltas)
	}
	return errors.New("object given as Process argument is not Deltas")
}

实际上http请求而言，http response关闭后http的访问就结束了，本地加锁仅仅会影响本地的执行效率，api-server无影响

 

根源

从代码分析，两种写法没有区别，对API-Server造成的影响仅仅是Http response的解析，老式写法解析后直接返回，新式写法的意思是创建结构体，然后结构体去处理值，并带上了超时时间。

那么为什么API-Server觉得一次请求时间很长呢，比如List的过程（Watch是长轮询，不涉及请求时长），根源在于API-Server在低版本（测试版本1.20.x）分页参数会失效。笔者自己尝试的1.25.4分页是有效的。估计是中间某次提交修复了，笔者在github看到很多关于List的提交优化

还有

 

 

1.25.4的API-Server的List过程

func ListResource(r rest.Lister, rw rest.Watcher, scope *RequestScope, forceWatch bool, minRequestTimeout time.Duration) http.HandlerFunc {
	return func(w http.ResponseWriter, req *http.Request) {
		// For performance tracking purposes. 创建埋点
		trace := utiltrace.New("List", traceFields(req)...)

		namespace, err := scope.Namer.Namespace(req)
		if err != nil {
			scope.err(err, w, req)
			return
		}

		// Watches for single objects are routed to this function.
		// Treat a name parameter the same as a field selector entry.
		hasName := true
		_, name, err := scope.Namer.Name(req)
		if err != nil {
			hasName = false
		}

		ctx := req.Context()
		ctx = request.WithNamespace(ctx, namespace)

		outputMediaType, _, err := negotiation.NegotiateOutputMediaType(req, scope.Serializer, scope)
		if err != nil {
			scope.err(err, w, req)
			return
		}

		opts := metainternalversion.ListOptions{}
		if err := metainternalversionscheme.ParameterCodec.DecodeParameters(req.URL.Query(), scope.MetaGroupVersion, &opts); err != nil {
			err = errors.NewBadRequest(err.Error())
			scope.err(err, w, req)
			return
		}

		if errs := metainternalversionvalidation.ValidateListOptions(&opts); len(errs) > 0 {
			err := errors.NewInvalid(schema.GroupKind{Group: metav1.GroupName, Kind: "ListOptions"}, "", errs)
			scope.err(err, w, req)
			return
		}

		// transform fields
		// TODO: DecodeParametersInto should do this.
		if opts.FieldSelector != nil {
			fn := func(label, value string) (newLabel, newValue string, err error) {
				return scope.Convertor.ConvertFieldLabel(scope.Kind, label, value)
			}
			if opts.FieldSelector, err = opts.FieldSelector.Transform(fn); err != nil {
				// TODO: allow bad request to set field causes based on query parameters
				err = errors.NewBadRequest(err.Error())
				scope.err(err, w, req)
				return
			}
		}

		if hasName {
			// metadata.name is the canonical internal name.
			// SelectionPredicate will notice that this is a request for
			// a single object and optimize the storage query accordingly.
			nameSelector := fields.OneTermEqualSelector("metadata.name", name)

			// Note that fieldSelector setting explicitly the "metadata.name"
			// will result in reaching this branch (as the value of that field
			// is propagated to requestInfo as the name parameter.
			// That said, the allowed field selectors in this branch are:
			// nil, fields.Everything and field selector matching metadata.name
			// for our name.
			if opts.FieldSelector != nil && !opts.FieldSelector.Empty() {
				selectedName, ok := opts.FieldSelector.RequiresExactMatch("metadata.name")
				if !ok || name != selectedName {
					scope.err(errors.NewBadRequest("fieldSelector metadata.name doesn't match requested name"), w, req)
					return
				}
			} else {
				opts.FieldSelector = nameSelector
			}
		}

		if opts.Watch || forceWatch {
			if rw == nil {
				scope.err(errors.NewMethodNotSupported(scope.Resource.GroupResource(), "watch"), w, req)
				return
			}
			// TODO: Currently we explicitly ignore ?timeout= and use only ?timeoutSeconds=.
			timeout := time.Duration(0)
			if opts.TimeoutSeconds != nil {
				timeout = time.Duration(*opts.TimeoutSeconds) * time.Second
			}
			if timeout == 0 && minRequestTimeout > 0 {
				timeout = time.Duration(float64(minRequestTimeout) * (rand.Float64() + 1.0))
			}
			klog.V(3).InfoS("Starting watch", "path", req.URL.Path, "resourceVersion", opts.ResourceVersion, "labels", opts.LabelSelector, "fields", opts.FieldSelector, "timeout", timeout)
			ctx, cancel := context.WithTimeout(ctx, timeout)
			defer cancel()
			watcher, err := rw.Watch(ctx, &opts)
			if err != nil {
				scope.err(err, w, req)
				return
			}
			requestInfo, _ := request.RequestInfoFrom(ctx)
			metrics.RecordLongRunning(req, requestInfo, metrics.APIServerComponent, func() {
				serveWatch(watcher, scope, outputMediaType, req, w, timeout)
			})
			return
		}

		// Log only long List requests (ignore Watch).
		defer trace.LogIfLong(500 * time.Millisecond) //超过500ms就埋点打印日志，这个埋点非常好用，建议使用
		trace.Step("About to List from storage")
		result, err := r.List(ctx, &opts) //API-Server实际上也是去ETCD取数据
		if err != nil {
			scope.err(err, w, req)
			return
		}
		trace.Step("Listing from storage done")
		defer trace.Step("Writing http response done", utiltrace.Field{"count", meta.LenList(result)})
		transformResponseObject(ctx, scope, trace, req, w, http.StatusOK, outputMediaType, result)
	}

可以看出超过500毫秒就会打印数据，笔者测试差不多500个pod的List就是差不多500毫秒少一点，Client-Go设计默认分页参数就是500条，😅精确设计。

// GetList implements storage.Interface.
func (s *store) GetList(ctx context.Context, key string, opts storage.ListOptions, listObj runtime.Object) error {
	preparedKey, err := s.prepareKey(key)
	if err != nil {
		return err
	}
	recursive := opts.Recursive
	resourceVersion := opts.ResourceVersion
	match := opts.ResourceVersionMatch
	pred := opts.Predicate
	trace := utiltrace.New(fmt.Sprintf("List(recursive=%v) etcd3", recursive),
		utiltrace.Field{"audit-id", endpointsrequest.GetAuditIDTruncated(ctx)},
		utiltrace.Field{"key", key},
		utiltrace.Field{"resourceVersion", resourceVersion},
		utiltrace.Field{"resourceVersionMatch", match},
		utiltrace.Field{"limit", pred.Limit},
		utiltrace.Field{"continue", pred.Continue})
	defer trace.LogIfLong(500 * time.Millisecond)
	listPtr, err := meta.GetItemsPtr(listObj)
	if err != nil {
		return err
	}
	v, err := conversion.EnforcePtr(listPtr)
	if err != nil || v.Kind() != reflect.Slice {
		return fmt.Errorf("need ptr to slice: %v", err)
	}

去读取ETCD3的数据，可以试试把k8s的低版本安装上debug试试。分析limit失效的原因，笔者是高版本的K8S，是已经修复版本。自定义的埋点List的代码

package main

import (
	"context"
	"fmt"
	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/meta"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/fields"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/watch"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/tools/pager"
	"k8s.io/utils/trace"
	"time"
)

func TimeNewFilteredPodInformer(client *kubernetes.Clientset) error {
	options := metav1.ListOptions{ResourceVersion: "0"}

	initTrace := trace.New("Reflector ListAndWatch", trace.Field{Key: "name", Value: r.name})
	defer initTrace.LogIfLong(1 * time.Millisecond)
	var list runtime.Object
	var paginatedResult bool
	var err error
	listCh := make(chan struct{}, 1)
	panicCh := make(chan interface{}, 1)
	go func() {
		defer func() {
			if r := recover(); r != nil {
				panicCh <- r
			}
		}()
		// Attempt to gather list in chunks, if supported by listerWatcher, if not, the first
		// list request will return the full response.
		pager := pager.New(pager.SimplePageFunc(func(opts metav1.ListOptions) (runtime.Object, error) {
			lw := &cache.ListWatch{
				ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
					return client.CoreV1().Pods(v1.NamespaceAll).List(context.TODO(), options)
				},
				WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
					return client.CoreV1().Pods(v1.NamespaceAll).Watch(context.TODO(), options)
				},
			}
			return lw.List(opts)
		}))

		list, paginatedResult, err = pager.List(context.Background(), options)
		initTrace.Step("Objects listed: ")
		fmt.Println("list END, is pager ", paginatedResult)
		if err != nil {
			fmt.Println("error is : ", err.Error())
		}
		close(listCh)
	}()
	select {
	case r := <-panicCh:
		panic(r)
	case <-listCh:
	}

	initTrace.Step("Resource version extracted")
	items, err := meta.ExtractList(list)
	fmt.Println("list items size is : ", len(items))
	if err != nil {
		return fmt.Errorf("unable to understand list result %#v (%v)", list, err)
	}
	initTrace.Step("Objects extracted")
	return nil
}

func TimeNewIndexerInformer(client *kubernetes.Clientset) error {
	options := metav1.ListOptions{ResourceVersion: "0"}

	initTrace := trace.New("Reflector ListAndWatch", trace.Field{Key: "name", Value: r.name})
	defer initTrace.LogIfLong(1 * time.Millisecond)
	var list runtime.Object
	var paginatedResult bool
	var err error
	listCh := make(chan struct{}, 1)
	panicCh := make(chan interface{}, 1)
	go func() {
		defer func() {
			if r := recover(); r != nil {
				panicCh <- r
			}
		}()
		// Attempt to gather list in chunks, if supported by listerWatcher, if not, the first
		// list request will return the full response.
		pager := pager.New(pager.SimplePageFunc(func(opts metav1.ListOptions) (runtime.Object, error) {
			lw := cache.NewListWatchFromClient(client.CoreV1().RESTClient(), "pods", v1.NamespaceAll, fields.Everything())
			return lw.List(opts)
		}))

		list, paginatedResult, err = pager.List(context.Background(), options)
		initTrace.Step("Objects listed: ")
		fmt.Println("list END, is pager ", paginatedResult)
		if err != nil {
			fmt.Println("error is : ", err.Error())
		}
		close(listCh)
	}()
	select {
	case r := <-panicCh:
		panic(r)
	case <-listCh:
	}

	initTrace.Step("Resource version extracted")
	items, err := meta.ExtractList(list)
	fmt.Println("list items size is : ", len(items))
	if err != nil {
		return fmt.Errorf("unable to understand list result %#v (%v)", list, err)
	}
	initTrace.Step("Objects extracted")
	return nil
}

trace的包好用，这里使用的k8s的包，实际上sdk基础包也有相似的功能。

func (t *Trace) durationIsWithinThreshold() bool {
	if t.endTime == nil { // we don't assume incomplete traces meet the threshold
		return false
	}
	return t.threshold == nil || *t.threshold == 0 || t.endTime.Sub(t.startTime) >= *t.threshold
}

总结

知其然知其所以然，要想知道为什么分页不生效，需要自定义API-Server debug才行，看代码很难看出原因，因为K8S实际上估计设计的时候也考虑过这个。