k8s.io/kubernetes@v1.29.3/test/integration/scheduler/queue_test.go

/*
Copyright 2021 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package scheduler

import (
	"context"
	"fmt"
	"testing"
	"time"

	v1 "k8s.io/api/core/v1"
	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
	apiextensionsclient "k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset"
	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/uuid"
	"k8s.io/apimachinery/pkg/util/wait"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/kubernetes"
	featuregatetesting "k8s.io/component-base/featuregate/testing"
	"k8s.io/klog/v2"
	configv1 "k8s.io/kube-scheduler/config/v1"
	apiservertesting "k8s.io/kubernetes/cmd/kube-apiserver/app/testing"
	"k8s.io/kubernetes/pkg/features"
	"k8s.io/kubernetes/pkg/scheduler"
	configtesting "k8s.io/kubernetes/pkg/scheduler/apis/config/testing"
	"k8s.io/kubernetes/pkg/scheduler/framework"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/defaultbinder"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/names"
	frameworkruntime "k8s.io/kubernetes/pkg/scheduler/framework/runtime"
	st "k8s.io/kubernetes/pkg/scheduler/testing"
	testfwk "k8s.io/kubernetes/test/integration/framework"
	testutils "k8s.io/kubernetes/test/integration/util"
	imageutils "k8s.io/kubernetes/test/utils/image"
	"k8s.io/utils/pointer"
)

func TestSchedulingGates(t *testing.T) {
	tests := []struct {
		name                  string
		pods                  []*v1.Pod
		featureEnabled        bool
		want                  []string
		rmPodsSchedulingGates []int
		wantPostGatesRemoval  []string
	}{
		{
			name: "feature disabled, regular pods",
			pods: []*v1.Pod{
				st.MakePod().Name("p1").Container("pause").Obj(),
				st.MakePod().Name("p2").Container("pause").Obj(),
			},
			featureEnabled: false,
			want:           []string{"p1", "p2"},
		},
		{
			name: "feature enabled, regular pods",
			pods: []*v1.Pod{
				st.MakePod().Name("p1").Container("pause").Obj(),
				st.MakePod().Name("p2").Container("pause").Obj(),
			},
			featureEnabled: true,
			want:           []string{"p1", "p2"},
		},
		{
			name: "feature disabled, one pod carrying scheduling gates",
			pods: []*v1.Pod{
				st.MakePod().Name("p1").SchedulingGates([]string{"foo"}).Container("pause").Obj(),
				st.MakePod().Name("p2").Container("pause").Obj(),
			},
			featureEnabled: false,
			want:           []string{"p1", "p2"},
		},
		{
			name: "feature enabled, one pod carrying scheduling gates",
			pods: []*v1.Pod{
				st.MakePod().Name("p1").SchedulingGates([]string{"foo"}).Container("pause").Obj(),
				st.MakePod().Name("p2").Container("pause").Obj(),
			},
			featureEnabled: true,
			want:           []string{"p2"},
		},
		{
			name: "feature enabled, two pod carrying scheduling gates, and remove gates of one pod",
			pods: []*v1.Pod{
				st.MakePod().Name("p1").SchedulingGates([]string{"foo"}).Container("pause").Obj(),
				st.MakePod().Name("p2").SchedulingGates([]string{"bar"}).Container("pause").Obj(),
				st.MakePod().Name("p3").Container("pause").Obj(),
			},
			featureEnabled:        true,
			want:                  []string{"p3"},
			rmPodsSchedulingGates: []int{1}, // remove gates of 'p2'
			wantPostGatesRemoval:  []string{"p2"},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.PodSchedulingReadiness, tt.featureEnabled)()

			// Use zero backoff seconds to bypass backoffQ.
			// It's intended to not start the scheduler's queue, and hence to
			// not start any flushing logic. We will pop and schedule the Pods manually later.
			testCtx := testutils.InitTestSchedulerWithOptions(
				t,
				testutils.InitTestAPIServer(t, "pod-scheduling-gates", nil),
				0,
				scheduler.WithPodInitialBackoffSeconds(0),
				scheduler.WithPodMaxBackoffSeconds(0),
			)
			testutils.SyncSchedulerInformerFactory(testCtx)

			cs, ns, ctx := testCtx.ClientSet, testCtx.NS.Name, testCtx.Ctx
			for _, p := range tt.pods {
				p.Namespace = ns
				if _, err := cs.CoreV1().Pods(ns).Create(ctx, p, metav1.CreateOptions{}); err != nil {
					t.Fatalf("Failed to create Pod %q: %v", p.Name, err)
				}
			}

			// Wait for the pods to be present in the scheduling queue.
			if err := wait.PollUntilContextTimeout(ctx, time.Millisecond*200, wait.ForeverTestTimeout, false, func(ctx context.Context) (bool, error) {
				pendingPods, _ := testCtx.Scheduler.SchedulingQueue.PendingPods()
				return len(pendingPods) == len(tt.pods), nil
			}); err != nil {
				t.Fatal(err)
			}

			// Pop the expected pods out. They should be de-queueable.
			for _, wantPod := range tt.want {
				podInfo := testutils.NextPodOrDie(t, testCtx)
				if got := podInfo.Pod.Name; got != wantPod {
					t.Errorf("Want %v to be popped out, but got %v", wantPod, got)
				}
			}

			if len(tt.rmPodsSchedulingGates) == 0 {
				return
			}
			// Remove scheduling gates from the pod spec.
			for _, idx := range tt.rmPodsSchedulingGates {
				patch := `{"spec": {"schedulingGates": null}}`
				podName := tt.pods[idx].Name
				if _, err := cs.CoreV1().Pods(ns).Patch(ctx, podName, types.StrategicMergePatchType, []byte(patch), metav1.PatchOptions{}); err != nil {
					t.Fatalf("Failed to patch pod %v: %v", podName, err)
				}
			}
			// Pop the expected pods out. They should be de-queueable.
			for _, wantPod := range tt.wantPostGatesRemoval {
				podInfo := testutils.NextPodOrDie(t, testCtx)
				if got := podInfo.Pod.Name; got != wantPod {
					t.Errorf("Want %v to be popped out, but got %v", wantPod, got)
				}
			}
		})
	}
}

// TestCoreResourceEnqueue verify Pods failed by in-tree default plugins can be
// moved properly upon their registered events.
func TestCoreResourceEnqueue(t *testing.T) {
	// Use zero backoff seconds to bypass backoffQ.
	// It's intended to not start the scheduler's queue, and hence to
	// not start any flushing logic. We will pop and schedule the Pods manually later.
	testCtx := testutils.InitTestSchedulerWithOptions(
		t,
		testutils.InitTestAPIServer(t, "core-res-enqueue", nil),
		0,
		scheduler.WithPodInitialBackoffSeconds(0),
		scheduler.WithPodMaxBackoffSeconds(0),
	)
	testutils.SyncSchedulerInformerFactory(testCtx)

	defer testCtx.Scheduler.SchedulingQueue.Close()

	cs, ns, ctx := testCtx.ClientSet, testCtx.NS.Name, testCtx.Ctx
	// Create one Node with a taint.
	node := st.MakeNode().Name("fake-node").Capacity(map[v1.ResourceName]string{v1.ResourceCPU: "2"}).Obj()
	node.Spec.Taints = []v1.Taint{{Key: "foo", Effect: v1.TaintEffectNoSchedule}}
	if _, err := cs.CoreV1().Nodes().Create(ctx, node, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Failed to create Node %q: %v", node.Name, err)
	}

	// Create two Pods that are both unschedulable.
	// - Pod1 is a best-effort Pod, but doesn't have the required toleration.
	// - Pod2 requests a large amount of CPU resource that the node cannot fit.
	//   Note: Pod2 will fail the tainttoleration plugin b/c that's ordered prior to noderesources.
	// - Pod3 has the required toleration, but requests a non-existing PVC.
	pod1 := st.MakePod().Namespace(ns).Name("pod1").Container("image").Obj()
	pod2 := st.MakePod().Namespace(ns).Name("pod2").Req(map[v1.ResourceName]string{v1.ResourceCPU: "4"}).Obj()
	pod3 := st.MakePod().Namespace(ns).Name("pod3").Toleration("foo").PVC("pvc").Container("image").Obj()
	for _, pod := range []*v1.Pod{pod1, pod2, pod3} {
		if _, err := cs.CoreV1().Pods(ns).Create(ctx, pod, metav1.CreateOptions{}); err != nil {
			t.Fatalf("Failed to create Pod %q: %v", pod.Name, err)
		}
	}

	// Wait for the three pods to be present in the scheduling queue.
	if err := wait.PollUntilContextTimeout(ctx, time.Millisecond*200, wait.ForeverTestTimeout, false, func(ctx context.Context) (bool, error) {
		pendingPods, _ := testCtx.Scheduler.SchedulingQueue.PendingPods()
		return len(pendingPods) == 3, nil
	}); err != nil {
		t.Fatal(err)
	}

	// Pop the three pods out. They should be unschedulable.
	for i := 0; i < 3; i++ {
		podInfo := testutils.NextPodOrDie(t, testCtx)
		fwk, ok := testCtx.Scheduler.Profiles[podInfo.Pod.Spec.SchedulerName]
		if !ok {
			t.Fatalf("Cannot find the profile for Pod %v", podInfo.Pod.Name)
		}
		// Schedule the Pod manually.
		_, fitError := testCtx.Scheduler.SchedulePod(ctx, fwk, framework.NewCycleState(), podInfo.Pod)
		if fitError == nil {
			t.Fatalf("Expect Pod %v to fail at scheduling.", podInfo.Pod.Name)
		}
		testCtx.Scheduler.FailureHandler(ctx, fwk, podInfo, framework.NewStatus(framework.Unschedulable).WithError(fitError), nil, time.Now())
	}

	// Trigger a NodeTaintChange event.
	// We expect this event to trigger moving the test Pod from unschedulablePods to activeQ.
	node.Spec.Taints = nil
	if _, err := cs.CoreV1().Nodes().Update(ctx, node, metav1.UpdateOptions{}); err != nil {
		t.Fatalf("Failed to remove taints off the node: %v", err)
	}

	// Now we should be able to pop the Pod from activeQ again.
	podInfo := testutils.NextPodOrDie(t, testCtx)
	if podInfo.Attempts != 2 {
		t.Fatalf("Expected the Pod to be attempted 2 times, but got %v", podInfo.Attempts)
	}
	if got := podInfo.Pod.Name; got != "pod1" {
		t.Fatalf("Expected pod1 to be popped, but got %v", got)
	}

	// Pod2 and Pod3 are not expected to be popped out.
	// - Although the failure reason has been lifted, Pod2 still won't be moved to active due to
	//   the node event's preCheckForNode().
	// - Regarding Pod3, the NodeTaintChange event is irrelevant with its scheduling failure.
	podInfo = testutils.NextPod(t, testCtx)
	if podInfo != nil {
		t.Fatalf("Unexpected pod %v get popped out", podInfo.Pod.Name)
	}
}

var _ framework.FilterPlugin = &fakeCRPlugin{}
var _ framework.EnqueueExtensions = &fakeCRPlugin{}

type fakeCRPlugin struct{}

func (f *fakeCRPlugin) Name() string {
	return "fakeCRPlugin"
}

func (f *fakeCRPlugin) Filter(_ context.Context, _ *framework.CycleState, _ *v1.Pod, _ *framework.NodeInfo) *framework.Status {
	return framework.NewStatus(framework.Unschedulable, "always fail")
}

// EventsToRegister returns the possible events that may make a Pod
// failed by this plugin schedulable.
func (f *fakeCRPlugin) EventsToRegister() []framework.ClusterEventWithHint {
	return []framework.ClusterEventWithHint{
		{Event: framework.ClusterEvent{Resource: "foos.v1.example.com", ActionType: framework.All}},
	}
}

// TestCustomResourceEnqueue constructs a fake plugin that registers custom resources
// to verify Pods failed by this plugin can be moved properly upon CR events.
func TestCustomResourceEnqueue(t *testing.T) {
	// Start API Server with apiextensions supported.
	server := apiservertesting.StartTestServerOrDie(
		t, apiservertesting.NewDefaultTestServerOptions(),
		[]string{"--disable-admission-plugins=ServiceAccount,TaintNodesByCondition", "--runtime-config=api/all=true"},
		testfwk.SharedEtcd(),
	)
	testCtx := &testutils.TestContext{}
	ctx, cancel := context.WithCancel(context.Background())
	testCtx.Ctx = ctx
	testCtx.CloseFn = func() {
		cancel()
		server.TearDownFn()
	}

	apiExtensionClient := apiextensionsclient.NewForConfigOrDie(server.ClientConfig)
	dynamicClient := dynamic.NewForConfigOrDie(server.ClientConfig)

	// Create a Foo CRD.
	fooCRD := &apiextensionsv1.CustomResourceDefinition{
		ObjectMeta: metav1.ObjectMeta{
			Name: "foos.example.com",
		},
		Spec: apiextensionsv1.CustomResourceDefinitionSpec{
			Group: "example.com",
			Scope: apiextensionsv1.NamespaceScoped,
			Names: apiextensionsv1.CustomResourceDefinitionNames{
				Plural: "foos",
				Kind:   "Foo",
			},
			Versions: []apiextensionsv1.CustomResourceDefinitionVersion{
				{
					Name:    "v1",
					Served:  true,
					Storage: true,
					Schema: &apiextensionsv1.CustomResourceValidation{
						OpenAPIV3Schema: &apiextensionsv1.JSONSchemaProps{
							Type: "object",
							Properties: map[string]apiextensionsv1.JSONSchemaProps{
								"field": {Type: "string"},
							},
						},
					},
				},
			},
		},
	}
	var err error
	fooCRD, err = apiExtensionClient.ApiextensionsV1().CustomResourceDefinitions().Create(testCtx.Ctx, fooCRD, metav1.CreateOptions{})
	if err != nil {
		t.Fatal(err)
	}

	registry := frameworkruntime.Registry{
		"fakeCRPlugin": func(_ context.Context, _ runtime.Object, fh framework.Handle) (framework.Plugin, error) {
			return &fakeCRPlugin{}, nil
		},
	}
	cfg := configtesting.V1ToInternalWithDefaults(t, configv1.KubeSchedulerConfiguration{
		Profiles: []configv1.KubeSchedulerProfile{{
			SchedulerName: pointer.String(v1.DefaultSchedulerName),
			Plugins: &configv1.Plugins{
				Filter: configv1.PluginSet{
					Enabled: []configv1.Plugin{
						{Name: "fakeCRPlugin"},
					},
				},
			},
		}}})

	testCtx.KubeConfig = server.ClientConfig
	testCtx.ClientSet = kubernetes.NewForConfigOrDie(server.ClientConfig)
	testCtx.NS, err = testCtx.ClientSet.CoreV1().Namespaces().Create(testCtx.Ctx, &v1.Namespace{
		ObjectMeta: metav1.ObjectMeta{Name: fmt.Sprintf("cr-enqueue-%v", string(uuid.NewUUID()))}}, metav1.CreateOptions{})
	if err != nil && !errors.IsAlreadyExists(err) {
		t.Fatalf("Failed to integration test ns: %v", err)
	}

	// Use zero backoff seconds to bypass backoffQ.
	// It's intended to not start the scheduler's queue, and hence to
	// not start any flushing logic. We will pop and schedule the Pods manually later.
	testCtx = testutils.InitTestSchedulerWithOptions(
		t,
		testCtx,
		0,
		scheduler.WithProfiles(cfg.Profiles...),
		scheduler.WithFrameworkOutOfTreeRegistry(registry),
		scheduler.WithPodInitialBackoffSeconds(0),
		scheduler.WithPodMaxBackoffSeconds(0),
	)
	testutils.SyncSchedulerInformerFactory(testCtx)

	defer testutils.CleanupTest(t, testCtx)

	cs, ns, ctx := testCtx.ClientSet, testCtx.NS.Name, testCtx.Ctx
	logger := klog.FromContext(ctx)
	// Create one Node.
	node := st.MakeNode().Name("fake-node").Obj()
	if _, err := cs.CoreV1().Nodes().Create(ctx, node, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Failed to create Node %q: %v", node.Name, err)
	}

	// Create a testing Pod.
	pause := imageutils.GetPauseImageName()
	pod := st.MakePod().Namespace(ns).Name("fake-pod").Container(pause).Obj()
	if _, err := cs.CoreV1().Pods(ns).Create(ctx, pod, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Failed to create Pod %q: %v", pod.Name, err)
	}

	// Wait for the testing Pod to be present in the scheduling queue.
	if err := wait.PollUntilContextTimeout(ctx, time.Millisecond*200, wait.ForeverTestTimeout, false, func(ctx context.Context) (bool, error) {
		pendingPods, _ := testCtx.Scheduler.SchedulingQueue.PendingPods()
		return len(pendingPods) == 1, nil
	}); err != nil {
		t.Fatal(err)
	}

	// Pop fake-pod out. It should be unschedulable.
	podInfo := testutils.NextPodOrDie(t, testCtx)
	fwk, ok := testCtx.Scheduler.Profiles[podInfo.Pod.Spec.SchedulerName]
	if !ok {
		t.Fatalf("Cannot find the profile for Pod %v", podInfo.Pod.Name)
	}
	// Schedule the Pod manually.
	_, fitError := testCtx.Scheduler.SchedulePod(ctx, fwk, framework.NewCycleState(), podInfo.Pod)
	// The fitError is expected to be non-nil as it failed the fakeCRPlugin plugin.
	if fitError == nil {
		t.Fatalf("Expect Pod %v to fail at scheduling.", podInfo.Pod.Name)
	}
	testCtx.Scheduler.FailureHandler(ctx, fwk, podInfo, framework.NewStatus(framework.Unschedulable).WithError(fitError), nil, time.Now())

	// Scheduling cycle is incremented from 0 to 1 after NextPod() is called, so
	// pass a number larger than 1 to move Pod to unschedulablePods.
	testCtx.Scheduler.SchedulingQueue.AddUnschedulableIfNotPresent(logger, podInfo, 10)

	// Trigger a Custom Resource event.
	// We expect this event to trigger moving the test Pod from unschedulablePods to activeQ.
	crdGVR := schema.GroupVersionResource{Group: fooCRD.Spec.Group, Version: fooCRD.Spec.Versions[0].Name, Resource: "foos"}
	crClient := dynamicClient.Resource(crdGVR).Namespace(ns)
	if _, err := crClient.Create(ctx, &unstructured.Unstructured{
		Object: map[string]interface{}{
			"apiVersion": "example.com/v1",
			"kind":       "Foo",
			"metadata":   map[string]interface{}{"name": "foo1"},
		},
	}, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Unable to create cr: %v", err)
	}

	// Now we should be able to pop the Pod from activeQ again.
	podInfo = testutils.NextPodOrDie(t, testCtx)
	if podInfo.Attempts != 2 {
		t.Errorf("Expected the Pod to be attempted 2 times, but got %v", podInfo.Attempts)
	}
}

// TestRequeueByBindFailure verify Pods failed by bind plugin are
// put back to the queue regardless of whether event happens or not.
func TestRequeueByBindFailure(t *testing.T) {
	fakeBind := &firstFailBindPlugin{}
	registry := frameworkruntime.Registry{
		"firstFailBindPlugin": func(ctx context.Context, o runtime.Object, fh framework.Handle) (framework.Plugin, error) {
			binder, err := defaultbinder.New(ctx, nil, fh)
			if err != nil {
				return nil, err
			}

			fakeBind.defaultBinderPlugin = binder.(framework.BindPlugin)
			return fakeBind, nil
		},
	}

	cfg := configtesting.V1ToInternalWithDefaults(t, configv1.KubeSchedulerConfiguration{
		Profiles: []configv1.KubeSchedulerProfile{{
			SchedulerName: pointer.String(v1.DefaultSchedulerName),
			Plugins: &configv1.Plugins{
				MultiPoint: configv1.PluginSet{
					Enabled: []configv1.Plugin{
						{Name: "firstFailBindPlugin"},
					},
					Disabled: []configv1.Plugin{
						{Name: names.DefaultBinder},
					},
				},
			},
		}}})

	// Use zero backoff seconds to bypass backoffQ.
	testCtx := testutils.InitTestSchedulerWithOptions(
		t,
		testutils.InitTestAPIServer(t, "core-res-enqueue", nil),
		0,
		scheduler.WithPodInitialBackoffSeconds(0),
		scheduler.WithPodMaxBackoffSeconds(0),
		scheduler.WithProfiles(cfg.Profiles...),
		scheduler.WithFrameworkOutOfTreeRegistry(registry),
	)
	testutils.SyncSchedulerInformerFactory(testCtx)

	go testCtx.Scheduler.Run(testCtx.Ctx)

	cs, ns, ctx := testCtx.ClientSet, testCtx.NS.Name, testCtx.Ctx
	node := st.MakeNode().Name("fake-node").Obj()
	if _, err := cs.CoreV1().Nodes().Create(ctx, node, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Failed to create Node %q: %v", node.Name, err)
	}
	// create a pod.
	pod := st.MakePod().Namespace(ns).Name("pod-1").Container(imageutils.GetPauseImageName()).Obj()
	if _, err := cs.CoreV1().Pods(ns).Create(ctx, pod, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Failed to create Pod %q: %v", pod.Name, err)
	}

	// 1. first binding try should fail.
	// 2. The pod should be enqueued to activeQ/backoffQ without any event.
	// 3. The pod should be scheduled in the second binding try.
	// Here, waiting until (3).
	err := wait.PollUntilContextTimeout(ctx, 200*time.Millisecond, wait.ForeverTestTimeout, false, testutils.PodScheduled(cs, ns, pod.Name))
	if err != nil {
		t.Fatalf("Expect pod-1 to be scheduled by the bind plugin: %v", err)
	}

	// Make sure the first binding trial was failed, and this pod is scheduled at the second trial.
	if fakeBind.counter != 1 {
		t.Fatalf("Expect pod-1 to be scheduled by the bind plugin in the second binding try: %v", err)
	}
}

// firstFailBindPlugin rejects the Pod in the first Bind call.
type firstFailBindPlugin struct {
	counter             int
	defaultBinderPlugin framework.BindPlugin
}

func (*firstFailBindPlugin) Name() string {
	return "firstFailBindPlugin"
}

func (p *firstFailBindPlugin) Bind(ctx context.Context, state *framework.CycleState, pod *v1.Pod, nodename string) *framework.Status {
	if p.counter == 0 {
		// fail in the first Bind call.
		p.counter++
		return framework.NewStatus(framework.Error, "firstFailBindPlugin rejects the Pod")
	}

	return p.defaultBinderPlugin.Bind(ctx, state, pod, nodename)
}

// TestRequeueByPermitRejection verify Pods failed by permit plugins in the binding cycle are
// put back to the queue, according to the correct scheduling cycle number.
func TestRequeueByPermitRejection(t *testing.T) {
	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.SchedulerQueueingHints, true)()
	queueingHintCalledCounter := 0
	fakePermit := &fakePermitPlugin{}
	registry := frameworkruntime.Registry{
		fakePermitPluginName: func(ctx context.Context, o runtime.Object, fh framework.Handle) (framework.Plugin, error) {
			fakePermit = &fakePermitPlugin{
				frameworkHandler: fh,
				schedulingHint: func(logger klog.Logger, pod *v1.Pod, oldObj, newObj interface{}) (framework.QueueingHint, error) {
					queueingHintCalledCounter++
					return framework.Queue, nil
				},
			}
			return fakePermit, nil
		},
	}
	cfg := configtesting.V1ToInternalWithDefaults(t, configv1.KubeSchedulerConfiguration{
		Profiles: []configv1.KubeSchedulerProfile{{
			SchedulerName: pointer.String(v1.DefaultSchedulerName),
			Plugins: &configv1.Plugins{
				MultiPoint: configv1.PluginSet{
					Enabled: []configv1.Plugin{
						{Name: fakePermitPluginName},
					},
				},
			},
		}}})

	// Use zero backoff seconds to bypass backoffQ.
	testCtx := testutils.InitTestSchedulerWithOptions(
		t,
		testutils.InitTestAPIServer(t, "core-res-enqueue", nil),
		0,
		scheduler.WithPodInitialBackoffSeconds(0),
		scheduler.WithPodMaxBackoffSeconds(0),
		scheduler.WithProfiles(cfg.Profiles...),
		scheduler.WithFrameworkOutOfTreeRegistry(registry),
	)
	testutils.SyncSchedulerInformerFactory(testCtx)

	go testCtx.Scheduler.Run(testCtx.Ctx)

	cs, ns, ctx := testCtx.ClientSet, testCtx.NS.Name, testCtx.Ctx
	node := st.MakeNode().Name("fake-node").Obj()
	if _, err := cs.CoreV1().Nodes().Create(ctx, node, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Failed to create Node %q: %v", node.Name, err)
	}
	// create a pod.
	pod := st.MakePod().Namespace(ns).Name("pod-1").Container(imageutils.GetPauseImageName()).Obj()
	if _, err := cs.CoreV1().Pods(ns).Create(ctx, pod, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Failed to create Pod %q: %v", pod.Name, err)
	}

	// update node label. (causes the NodeUpdate event)
	node.Labels = map[string]string{"updated": ""}
	if _, err := cs.CoreV1().Nodes().Update(ctx, node, metav1.UpdateOptions{}); err != nil {
		t.Fatalf("Failed to add labels to the node: %v", err)
	}

	// create a pod to increment the scheduling cycle number in the scheduling queue.
	// We can make sure NodeUpdate event, that has happened in the previous scheduling cycle, makes Pod to be enqueued to activeQ via the scheduling queue.
	pod = st.MakePod().Namespace(ns).Name("pod-2").Container(imageutils.GetPauseImageName()).Obj()
	if _, err := cs.CoreV1().Pods(ns).Create(ctx, pod, metav1.CreateOptions{}); err != nil {
		t.Fatalf("Failed to create Pod %q: %v", pod.Name, err)
	}

	// reject pod-1 to simulate the failure in Permit plugins.
	// This pod-1 should be enqueued to activeQ because the NodeUpdate event has happened.
	fakePermit.frameworkHandler.IterateOverWaitingPods(func(wp framework.WaitingPod) {
		if wp.GetPod().Name == "pod-1" {
			wp.Reject(fakePermitPluginName, "fakePermitPlugin rejects the Pod")
			return
		}
	})

	// Wait for pod-2 to be scheduled.
	err := wait.PollUntilContextTimeout(ctx, 200*time.Millisecond, wait.ForeverTestTimeout, false, func(ctx context.Context) (done bool, err error) {
		fakePermit.frameworkHandler.IterateOverWaitingPods(func(wp framework.WaitingPod) {
			if wp.GetPod().Name == "pod-2" {
				wp.Allow(fakePermitPluginName)
			}
		})

		return testutils.PodScheduled(cs, ns, "pod-2")(ctx)
	})
	if err != nil {
		t.Fatalf("Expect pod-2 to be scheduled")
	}

	err = wait.PollUntilContextTimeout(ctx, 200*time.Millisecond, wait.ForeverTestTimeout, false, func(ctx context.Context) (done bool, err error) {
		pod1Found := false
		fakePermit.frameworkHandler.IterateOverWaitingPods(func(wp framework.WaitingPod) {
			if wp.GetPod().Name == "pod-1" {
				pod1Found = true
				wp.Allow(fakePermitPluginName)
			}
		})
		return pod1Found, nil
	})
	if err != nil {
		t.Fatal("Expect pod-1 to be scheduled again")
	}

	if queueingHintCalledCounter != 1 {
		t.Fatalf("Expected the scheduling hint to be called 1 time, but %v", queueingHintCalledCounter)
	}
}

type fakePermitPlugin struct {
	frameworkHandler framework.Handle
	schedulingHint   framework.QueueingHintFn
}

const fakePermitPluginName = "fakePermitPlugin"

func (p *fakePermitPlugin) Name() string {
	return fakePermitPluginName
}

func (p *fakePermitPlugin) Permit(ctx context.Context, state *framework.CycleState, _ *v1.Pod, _ string) (*framework.Status, time.Duration) {
	return framework.NewStatus(framework.Wait), wait.ForeverTestTimeout
}

func (p *fakePermitPlugin) EventsToRegister() []framework.ClusterEventWithHint {
	return []framework.ClusterEventWithHint{
		{Event: framework.ClusterEvent{Resource: framework.Node, ActionType: framework.UpdateNodeLabel}, QueueingHintFn: p.schedulingHint},
	}
}