client-go/consistencydetector: introduce CheckWatchListFromCacheDataConsistencyIfRequested

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

@@ -36,6 +36,12 @@ var (
 	emptyListOptions = metav1.ListOptions{}
 )
 
+func TestDriveCheckWatchListFromCacheDataConsistencyIfRequested(t *testing.T) {
+	ctx := context.TODO()
+
+	CheckWatchListFromCacheDataConsistencyIfRequested(ctx, "", emptyListFunc, emptyListOptions, &v1.PodList{})
+}
+
 func TestDriveCheckListFromCacheDataConsistencyIfRequested(t *testing.T) {
 	ctx := context.TODO()
 

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

@@ -0,0 +1,54 @@
+/*
+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 consistencydetector
+
+import (
+	"context"
+	"os"
+	"strconv"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+var dataConsistencyDetectionForWatchListEnabled = false
+
+func init() {
+	dataConsistencyDetectionForWatchListEnabled, _ = strconv.ParseBool(os.Getenv("KUBE_WATCHLIST_INCONSISTENCY_DETECTOR"))
+}
+
+// IsDataConsistencyDetectionForWatchListEnabled returns true when
+// the KUBE_WATCHLIST_INCONSISTENCY_DETECTOR environment variable was set during a binary startup.
+func IsDataConsistencyDetectionForWatchListEnabled() bool {
+	return dataConsistencyDetectionForWatchListEnabled
+}
+
+// CheckWatchListFromCacheDataConsistencyIfRequested performs a data consistency check only when
+// the KUBE_WATCHLIST_INCONSISTENCY_DETECTOR environment variable was set during a binary startup.
+//
+// The consistency check is meant to be enforced only in the CI, not in production.
+// The check ensures that data retrieved by the watch-list api call
+// is exactly the same as data received by the standard list api call against etcd.
+//
+// Note that this function will panic when data inconsistency is detected.
+// This is intentional because we want to catch it in the CI.
+func CheckWatchListFromCacheDataConsistencyIfRequested[T runtime.Object](ctx context.Context, identity string, listItemsFn ListFunc[T], optionsUsedToReceiveList metav1.ListOptions, receivedList runtime.Object) {
+	if !IsDataConsistencyDetectionForWatchListEnabled() {
+		return
+	}
+	checkListFromCacheDataConsistencyIfRequestedInternal(ctx, identity, listItemsFn, optionsUsedToReceiveList, receivedList)
+}