Add unit tests for Data Consistency Detector

staging/src/k8s.io/client-go/tools/cache/controller.go

@@ -596,16 +596,7 @@ func newInformer(clientState Store, options InformerOptions) Controller {
 	// KeyLister, that way resync operations will result in the correct set
 	// of update/delete deltas.
 
-	var fifo Queue
-	if clientgofeaturegate.FeatureGates().Enabled(clientgofeaturegate.InOrderInformers) {
-		fifo = NewRealFIFO(MetaNamespaceKeyFunc, clientState, options.Transform)
-	} else {
-		fifo = NewDeltaFIFOWithOptions(DeltaFIFOOptions{
-			KnownObjects:          clientState,
-			EmitDeltaTypeReplaced: true,
-			Transformer:           options.Transform,
-		})
-	}
+	fifo := newQueueFIFO(clientState, options.Transform)
 
 	cfg := &Config{
 		Queue:            fifo,
@@ -623,3 +614,15 @@ func newInformer(clientState Store, options InformerOptions) Controller {
 	}
 	return New(cfg)
 }
+
+func newQueueFIFO(clientState Store, transform TransformFunc) Queue {
+	if clientgofeaturegate.FeatureGates().Enabled(clientgofeaturegate.InOrderInformers) {
+		return NewRealFIFO(MetaNamespaceKeyFunc, clientState, transform)
+	} else {
+		return NewDeltaFIFOWithOptions(DeltaFIFOOptions{
+			KnownObjects:          clientState,
+			EmitDeltaTypeReplaced: true,
+			Transformer:           transform,
+		})
+	}
+}

staging/src/k8s.io/client-go/tools/cache/reflector_data_consistency_detector_test.go

@@ -0,0 +1,114 @@
+/*
+Copyright 2024 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 cache
+
+import (
+	"context"
+	"fmt"
+	"testing"
+	"time"
+
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/apimachinery/pkg/watch"
+	clientfeatures "k8s.io/client-go/features"
+	clientfeaturestesting "k8s.io/client-go/features/testing"
+	"k8s.io/client-go/util/consistencydetector"
+	"k8s.io/klog/v2/ktesting"
+)
+
+func TestReflectorDataConsistencyDetector(t *testing.T) {
+	clientfeaturestesting.SetFeatureDuringTest(t, clientfeatures.WatchListClient, true)
+	restore := consistencydetector.SetDataConsistencyDetectionForWatchListEnabledForTest(true)
+	defer restore()
+
+	markTransformed := func(obj interface{}) (interface{}, error) {
+		pod, ok := obj.(*v1.Pod)
+		if !ok {
+			return obj, nil
+		}
+		newPod := pod.DeepCopy()
+		if newPod.Labels == nil {
+			newPod.Labels = make(map[string]string)
+		}
+		newPod.Labels["transformed"] = "true"
+		return newPod, nil
+	}
+
+	for _, inOrder := range []bool{false, true} {
+		t.Run(fmt.Sprintf("InOrder=%v", inOrder), func(t *testing.T) {
+			clientfeaturestesting.SetFeatureDuringTest(t, clientfeatures.InOrderInformers, inOrder)
+			for _, transformerEnabled := range []bool{false, true} {
+				var transformer TransformFunc
+				if transformerEnabled {
+					transformer = markTransformed
+				}
+				t.Run(fmt.Sprintf("Transformer=%v", transformerEnabled), func(t *testing.T) {
+					runTestReflectorDataConsistencyDetector(t, transformer)
+				})
+			}
+		})
+	}
+}
+
+func runTestReflectorDataConsistencyDetector(t *testing.T, transformer TransformFunc) {
+	_, ctx := ktesting.NewTestContext(t)
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	store := NewStore(MetaNamespaceKeyFunc)
+	fifo := newQueueFIFO(store, transformer)
+
+	lw := &ListWatch{
+		ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+			return &v1.PodList{
+				ListMeta: metav1.ListMeta{ResourceVersion: "1"},
+				Items: []v1.Pod{
+					{ObjectMeta: metav1.ObjectMeta{Name: "pod-1", ResourceVersion: "1"}},
+				},
+			}, nil
+		},
+		WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+			w := watch.NewFake()
+			go func() {
+				w.Add(&v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "pod-1", ResourceVersion: "1"}})
+				w.Action(watch.Bookmark, &v1.Pod{ObjectMeta: metav1.ObjectMeta{
+					Name:            "pod-1",
+					ResourceVersion: "1",
+					Annotations:     map[string]string{metav1.InitialEventsAnnotationKey: "true"},
+				}})
+			}()
+			return w, nil
+		},
+	}
+
+	r := NewReflector(lw, &v1.Pod{}, fifo, 0)
+
+	go func() {
+		_ = wait.PollUntilContextTimeout(ctx, 10*time.Millisecond, 5*time.Second, true, func(ctx context.Context) (bool, error) {
+			return r.LastSyncResourceVersion() != "", nil
+		})
+		cancel()
+	}()
+
+	err := r.ListAndWatchWithContext(ctx)
+	if err != nil {
+		t.Errorf("ListAndWatchWithContext returned error: %v", err)
+	}
+}

staging/src/k8s.io/client-go/tools/cache/shared_informer.go

@@ -539,16 +539,7 @@ func (s *sharedIndexInformer) RunWithContext(ctx context.Context) {
 		s.startedLock.Lock()
 		defer s.startedLock.Unlock()
 
-		var fifo Queue
-		if clientgofeaturegate.FeatureGates().Enabled(clientgofeaturegate.InOrderInformers) {
-			fifo = NewRealFIFO(MetaNamespaceKeyFunc, s.indexer, s.transform)
-		} else {
-			fifo = NewDeltaFIFOWithOptions(DeltaFIFOOptions{
-				KnownObjects:          s.indexer,
-				EmitDeltaTypeReplaced: true,
-				Transformer:           s.transform,
-			})
-		}
+		fifo := newQueueFIFO(s.indexer, s.transform)
 
 		cfg := &Config{
 			Queue:             fifo,

staging/src/k8s.io/client-go/util/consistencydetector/data_consistency_detector.go

@@ -45,6 +45,16 @@ func IsDataConsistencyDetectionForWatchListEnabled() bool {
 	return dataConsistencyDetectionForWatchListEnabled
 }
 
+// SetDataConsistencyDetectionForWatchListEnabledForTest allows to enable/disable data consistency detection for testing purposes.
+// It returns a function that restores the original value.
+func SetDataConsistencyDetectionForWatchListEnabledForTest(enabled bool) func() {
+	original := dataConsistencyDetectionForWatchListEnabled
+	dataConsistencyDetectionForWatchListEnabled = enabled
+	return func() {
+		dataConsistencyDetectionForWatchListEnabled = original
+	}
+}
+
 type RetrieveItemsFunc[U any] func() []U
 
 type ListFunc[T runtime.Object] func(ctx context.Context, options metav1.ListOptions) (T, error)