kubernetes · valerian-roche · Jul 28, 2025 · Jul 31, 2025 · Aug 5, 2025
diff --git a/staging/src/k8s.io/client-go/tools/cache/delta_fifo.go b/staging/src/k8s.io/client-go/tools/cache/delta_fifo.go
@@ -270,7 +270,8 @@ func NewDeltaFIFOWithOptions(opts DeltaFIFOOptions) *DeltaFIFO {
 }
 
 var (
-	_ = Queue(&DeltaFIFO{}) // DeltaFIFO is a Queue
+	_ = Queue(&DeltaFIFO{})             // DeltaFIFO is a Queue
+	_ = TransformingStore(&DeltaFIFO{}) // DeltaFIFO implements TransformingStore to allow memory optimizations
 )
 
 var (

diff --git a/staging/src/k8s.io/client-go/tools/cache/delta_fifo_test.go b/staging/src/k8s.io/client-go/tools/cache/delta_fifo_test.go
@@ -28,7 +28,7 @@ import (
 // from the most recent Delta.
 // You should treat the items returned inside the deltas as immutable.
 // This function was moved here because it is not consistent with normal list semantics, but is used in unit testing.
-func (f *DeltaFIFO) List() []interface{} {
+func (f *DeltaFIFO) list() []interface{} {
 	f.lock.RLock()
 	defer f.lock.RUnlock()
 	return f.listLocked()
@@ -46,7 +46,7 @@ func (f *DeltaFIFO) listLocked() []interface{} {
 // ListKeys returns a list of all the keys of the objects currently
 // in the FIFO.
 // This function was moved here because it is not consistent with normal list semantics, but is used in unit testing.
-func (f *DeltaFIFO) ListKeys() []string {
+func (f *DeltaFIFO) listKeys() []string {
 	f.lock.RLock()
 	defer f.lock.RUnlock()
 	list := make([]string, 0, len(f.queue))
@@ -60,19 +60,19 @@ func (f *DeltaFIFO) ListKeys() []string {
 // or sets exists=false.
 // You should treat the items returned inside the deltas as immutable.
 // This function was moved here because it is not consistent with normal list semantics, but is used in unit testing.
-func (f *DeltaFIFO) Get(obj interface{}) (item interface{}, exists bool, err error) {
+func (f *DeltaFIFO) get(obj interface{}) (item interface{}, exists bool, err error) {
 	key, err := f.KeyOf(obj)
 	if err != nil {
 		return nil, false, KeyError{obj, err}
 	}
-	return f.GetByKey(key)
+	return f.getByKey(key)
 }
 
 // GetByKey returns the complete list of deltas for the requested item,
 // setting exists=false if that list is empty.
 // You should treat the items returned inside the deltas as immutable.
 // This function was moved here because it is not consistent with normal list semantics, but is used in unit testing.
-func (f *DeltaFIFO) GetByKey(key string) (item interface{}, exists bool, err error) {
+func (f *DeltaFIFO) getByKey(key string) (item interface{}, exists bool, err error) {
 	f.lock.RLock()
 	defer f.lock.RUnlock()
 	d, exists := f.items[key]
@@ -320,10 +320,10 @@ func TestDeltaFIFO_addUpdate(t *testing.T) {
 	f.Update(mkFifoObj("foo", 12))
 	f.Delete(mkFifoObj("foo", 15))
 
-	if e, a := []interface{}{mkFifoObj("foo", 15)}, f.List(); !reflect.DeepEqual(e, a) {
+	if e, a := []interface{}{mkFifoObj("foo", 15)}, f.list(); !reflect.DeepEqual(e, a) {
 		t.Errorf("Expected %+v, got %+v", e, a)
 	}
-	if e, a := []string{"foo"}, f.ListKeys(); !reflect.DeepEqual(e, a) {
+	if e, a := []string{"foo"}, f.listKeys(); !reflect.DeepEqual(e, a) {
 		t.Errorf("Expected %+v, got %+v", e, a)
 	}
 
@@ -349,7 +349,7 @@ func TestDeltaFIFO_addUpdate(t *testing.T) {
 		t.Errorf("Got second value %v", unexpected.val)
 	case <-time.After(50 * time.Millisecond):
 	}
-	_, exists, _ := f.Get(mkFifoObj("foo", ""))
+	_, exists, _ := f.get(mkFifoObj("foo", ""))
 	if exists {
 		t.Errorf("item did not get removed")
 	}
@@ -397,7 +397,7 @@ func TestDeltaFIFO_transformer(t *testing.T) {
 	must(f.Replace([]interface{}{}, ""))
 
 	// Should be empty
-	if e, a := []string{"foo", "bar"}, f.ListKeys(); !reflect.DeepEqual(e, a) {
+	if e, a := []string{"foo", "bar"}, f.listKeys(); !reflect.DeepEqual(e, a) {
 		t.Errorf("Expected %+v, got %+v", e, a)
 	}
 
@@ -507,7 +507,7 @@ func TestDeltaFIFO_addReplace(t *testing.T) {
 		t.Errorf("Got second value %v", unexpected.val)
 	case <-time.After(50 * time.Millisecond):
 	}
-	_, exists, _ := f.Get(mkFifoObj("foo", ""))
+	_, exists, _ := f.get(mkFifoObj("foo", ""))
 	if exists {
 		t.Errorf("item did not get removed")
 	}
@@ -991,7 +991,7 @@ func BenchmarkDeltaFIFOListKeys(b *testing.B) {
 	b.ResetTimer()
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
-			_ = f.ListKeys()
+			_ = f.listKeys()
 		}
 	})
 	b.StopTimer()

diff --git a/staging/src/k8s.io/client-go/tools/cache/reflector.go b/staging/src/k8s.io/client-go/tools/cache/reflector.go
@@ -80,7 +80,7 @@ type ReflectorStore interface {
 // TransformingStore is an optional interface that can be implemented by the provided store.
 // If implemented on the provided store reflector will use the same transformer in its internal stores.
 type TransformingStore interface {
-	Store
+	ReflectorStore
 	Transformer() TransformFunc
 }
 

diff --git a/staging/src/k8s.io/client-go/tools/cache/reflector_test.go b/staging/src/k8s.io/client-go/tools/cache/reflector_test.go
@@ -20,10 +20,12 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"maps"
 	"math/rand"
 	"net/http"
 	"reflect"
 	goruntime "runtime"
+	"slices"
 	"strconv"
 	"sync"
 	"sync/atomic"
@@ -1962,7 +1964,7 @@ func TestReflectorReplacesStoreOnUnsafeDelete(t *testing.T) {
 	s := NewFIFO(MetaNamespaceKeyFunc)
 	var replaceInvoked atomic.Int32
 	store := &fakeStore{
-		Store: s,
+		ReflectorStore: s,
 		beforeReplace: func(list []interface{}, rv string) {
 			// interested in the Replace call that happens after the Error event
 			if rv == lastExpectedRV {
@@ -2057,131 +2059,165 @@ func TestReflectorReplacesStoreOnUnsafeDelete(t *testing.T) {
 }
 
 func TestReflectorRespectStoreTransformer(t *testing.T) {
-	mkPod := func(id string, rv string) *v1.Pod {
-		return &v1.Pod{
-			ObjectMeta: metav1.ObjectMeta{Namespace: "ns", Name: id, ResourceVersion: rv},
-			Spec: v1.PodSpec{
-				Hostname: "test",
+	for name, test := range map[string]struct {
+		storeBuilder func(counter *atomic.Int32) ReflectorStore
+		items        func(rs ReflectorStore) []interface{}
+	}{
+		"real-fifo": {
+			storeBuilder: func(counter *atomic.Int32) ReflectorStore {
+				return NewRealFIFO(MetaNamespaceKeyFunc, NewStore(MetaNamespaceKeyFunc), func(i interface{}) (interface{}, error) {
+					counter.Add(1)
+					cast := i.(*v1.Pod)
+					cast.Spec.Hostname = "transformed"
+					return cast, nil
+				})
 			},
-		}
-	}
-
-	preExisting1 := mkPod("foo-1", "1")
-	preExisting2 := mkPod("foo-2", "2")
-	pod3 := mkPod("foo-3", "3")
-
-	lastExpectedRV := "3"
-	events := []watch.Event{
-		{Type: watch.Added, Object: preExisting1},
-		{Type: watch.Added, Object: preExisting2},
-		{Type: watch.Bookmark, Object: &v1.Pod{
-			ObjectMeta: metav1.ObjectMeta{
-				ResourceVersion: lastExpectedRV,
-				Annotations: map[string]string{
-					metav1.InitialEventsAnnotationKey: "true",
-				},
+			items: func(rs ReflectorStore) []interface{} {
+				store := rs.(*RealFIFO)
+				objects := make(map[string]interface{})
+				for _, item := range store.getItems() {
+					key, _ := store.keyFunc(item.Object)
+					if item.Type == Deleted {
+						delete(objects, key)
+					} else {
+						objects[key] = item.Object
+					}
+				}
+				return slices.Collect(maps.Values(objects))
 			},
-		}},
-		{Type: watch.Added, Object: pod3},
-	}
+		},
+		"delta-fifo": {
+			storeBuilder: func(counter *atomic.Int32) ReflectorStore {
+				return NewDeltaFIFOWithOptions(DeltaFIFOOptions{
+					KeyFunction: MetaNamespaceKeyFunc,
+					Transformer: func(i interface{}) (interface{}, error) {
+						counter.Add(1)
+						cast := i.(*v1.Pod)
+						cast.Spec.Hostname = "transformed"
+						return cast, nil
+					},
+				})
+			},
+			items: func(rs ReflectorStore) []interface{} {
+				return rs.(*DeltaFIFO).list()
+			},
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			mkPod := func(id string, rv string) *v1.Pod {
+				return &v1.Pod{
+					ObjectMeta: metav1.ObjectMeta{Namespace: "ns", Name: id, ResourceVersion: rv},
+					Spec: v1.PodSpec{
+						Hostname: "test",
+					},
+				}
+			}
 
-	s := NewFIFO(MetaNamespaceKeyFunc)
-	var replaceInvoked atomic.Int32
-	store := &fakeStore{
-		Store: s,
-		beforeReplace: func(list []interface{}, rv string) {
-			replaceInvoked.Add(1)
-			// Only two pods are present at the point when Replace is called.
-			if len(list) != 2 {
-				t.Errorf("unexpected nb of objects: expected 2 received %d", len(list))
+			preExisting1 := mkPod("foo-1", "1")
+			preExisting2 := mkPod("foo-2", "2")
+			pod3 := mkPod("foo-3", "3")
+
+			lastExpectedRV := "3"
+			events := []watch.Event{
+				{Type: watch.Added, Object: preExisting1},
+				{Type: watch.Added, Object: preExisting2},
+				{Type: watch.Bookmark, Object: &v1.Pod{
+					ObjectMeta: metav1.ObjectMeta{
+						ResourceVersion: lastExpectedRV,
+						Annotations: map[string]string{
+							metav1.InitialEventsAnnotationKey: "true",
+						},
+					},
+				}},
+				{Type: watch.Added, Object: pod3},
 			}
-			for _, obj := range list {
-				cast := obj.(*v1.Pod)
-				if cast.Spec.Hostname != "transformed" {
-					t.Error("Object was not transformed prior to replacement")
-				}
+
+			var transformerInvoked atomic.Int32
+			s := test.storeBuilder(&transformerInvoked)
+
+			var once sync.Once
+			lw := &ListWatch{
+				WatchFunc: func(metav1.ListOptions) (watch.Interface, error) {
+					fw := watch.NewFake()
+					go func() {
+						once.Do(func() {
+							for _, e := range events {
+								fw.Action(e.Type, e.Object)
+							}
+						})
+					}()
+					return fw, nil
+				},
+				// ListFunc should never be used in WatchList mode
+				ListFunc: func(metav1.ListOptions) (runtime.Object, error) {
+					return nil, errors.New("list call not expected in WatchList mode")
+				},
 			}
-		},
-		afterReplace: func(rv string, err error) {},
-		transformer: func(i interface{}) (interface{}, error) {
-			cast := i.(*v1.Pod)
-			cast.Spec.Hostname = "transformed"
-			return cast, nil
-		},
-	}
 
-	var once sync.Once
-	lw := &ListWatch{
-		WatchFunc: func(metav1.ListOptions) (watch.Interface, error) {
-			fw := watch.NewFake()
+			clientfeaturestesting.SetFeatureDuringTest(t, clientfeatures.WatchListClient, true)
+			r := NewReflector(lw, &v1.Pod{}, s, 0)
+			ctx, cancel := context.WithCancel(context.Background())
+			doneCh := make(chan struct{})
 			go func() {
-				once.Do(func() {
-					for _, e := range events {
-						fw.Action(e.Type, e.Object)
-					}
-				})
+				defer close(doneCh)
+				r.RunWithContext(ctx)
 			}()
-			return fw, nil
-		},
-		// ListFunc should never be used in WatchList mode
-		ListFunc: func(metav1.ListOptions) (runtime.Object, error) {
-			return nil, errors.New("list call not expected in WatchList mode")
-		},
-	}
 
-	clientfeaturestesting.SetFeatureDuringTest(t, clientfeatures.WatchListClient, true)
-	r := NewReflector(lw, &v1.Pod{}, store, 0)
-	ctx, cancel := context.WithCancel(context.Background())
-	doneCh := make(chan struct{})
-	go func() {
-		defer close(doneCh)
-		r.RunWithContext(ctx)
-	}()
+			// wait for the RV to sync to the version returned by the final list
+			err := wait.PollUntilContextTimeout(context.Background(), 100*time.Millisecond, 5*time.Second, true, func(ctx context.Context) (done bool, err error) {
+				if rv := r.LastSyncResourceVersion(); rv == lastExpectedRV {
+					return true, nil
+				}
+				return false, nil
+			})
+			if err != nil {
+				t.Fatalf("reflector never caught up with expected revision: %q, err: %v", lastExpectedRV, err)
+			}
 
-	// wait for the RV to sync to the version returned by the final list
-	err := wait.PollUntilContextTimeout(context.Background(), 100*time.Millisecond, 5*time.Second, true, func(ctx context.Context) (done bool, err error) {
-		if rv := r.LastSyncResourceVersion(); rv == lastExpectedRV {
-			return true, nil
-		}
-		return false, nil
-	})
-	if err != nil {
-		t.Fatalf("reflector never caught up with expected revision: %q, err: %v", lastExpectedRV, err)
-	}
+			if want, got := lastExpectedRV, r.LastSyncResourceVersion(); want != got {
+				t.Errorf("expected LastSyncResourceVersion to be %q, but got: %q", want, got)
+			}
 
-	if want, got := lastExpectedRV, r.LastSyncResourceVersion(); want != got {
-		t.Errorf("expected LastSyncResourceVersion to be %q, but got: %q", want, got)
-	}
-	if want, got := 1, int(replaceInvoked.Load()); want != got {
-		t.Errorf("expected replace to be invoked %d times, but got: %d", want, got)
-	}
+			informerItems := test.items(s)
+			if want, got := 3, len(informerItems); want != got {
+				t.Errorf("expected informer to contain %d objects, but got: %d", want, got)
+			}
+			for _, item := range informerItems {
+				cast := item.(*v1.Pod)
+				if cast.Spec.Hostname != "transformed" {
+					t.Error("Object was not transformed prior to replacement")
+				}
+			}
 
-	cancel()
-	select {
-	case <-doneCh:
-	case <-time.After(wait.ForeverTestTimeout):
-		t.Errorf("timed out waiting for Run to return")
+			// Transformer should have been invoked twice for the initial sync in the informer on the temporary store,
+			// then twice on replace, then once on the following update.
+			if want, got := 5, int(transformerInvoked.Load()); want != got {
+				t.Errorf("expected transformer to be invoked %d times, but got: %d", want, got)
+			}
+
+			cancel()
+			select {
+			case <-doneCh:
+			case <-time.After(wait.ForeverTestTimeout):
+				t.Errorf("timed out waiting for Run to return")
+			}
+		})
 	}
 }
 
 type fakeStore struct {
-	Store
+	ReflectorStore
 	beforeReplace func(list []interface{}, s string)
 	afterReplace  func(rv string, err error)
-	transformer   TransformFunc
 }
 
 func (f *fakeStore) Replace(list []interface{}, rv string) error {
 	f.beforeReplace(list, rv)
-	err := f.Store.Replace(list, rv)
+	err := f.ReflectorStore.Replace(list, rv)
 	f.afterReplace(rv, err)
 	return err
 }
 
-func (f *fakeStore) Transformer() TransformFunc {
-	return f.transformer
-}
-
 func BenchmarkExtractList(b *testing.B) {
 	_, _, podList := getPodListItems(0, fakeItemsNum)
 	_, _, configMapList := getConfigmapListItems(0, fakeItemsNum)
-Original file line number
+Diff line change
@@ Expand Up @@
     }
     var (
-    	_ = Queue(&DeltaFIFO{}) // DeltaFIFO is a Queue
+    	_ = Queue(&DeltaFIFO{})             // DeltaFIFO is a Queue
+    	_ = TransformingStore(&DeltaFIFO{}) // DeltaFIFO implements TransformingStore to allow memory optimizations
     )
     var (
@@ Expand Down @@