Harden watcher relist storage

event-exporter/kubernetes/watchers/storage.go

@@ -66,6 +66,11 @@ func (s *watcherStore) Delete(obj interface{}) error {
 	return nil
 }
 
+func (s *watcherStore) Replace(_ []interface{}, _ string) error {
+	// List responses are handled by watcher-specific OnList callbacks.
+	return nil
+}
+
 func newWatcherStore(config *WatcherStoreConfig) *watcherStore {
 	var cacheStorage cache.ReflectorStore
 	switch config.StorageType {

event-exporter/kubernetes/watchers/storage_test.go

@@ -0,0 +1,73 @@
+/*
+Copyright 2026 Google Inc.
+
+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 watchers
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/tools/cache"
+)
+
+func TestWatcherStoreReplaceDoesNotPopulateDeltaFIFO(t *testing.T) {
+	store := newWatcherStore(&WatcherStoreConfig{
+		KeyFunc:     cache.MetaNamespaceKeyFunc,
+		Handler:     cache.ResourceEventHandlerFuncs{},
+		StorageType: DeltaFIFOStorage,
+	})
+
+	err := store.Replace([]interface{}{
+		&corev1.Event{
+			ObjectMeta: metav1.ObjectMeta{
+				Namespace: "default",
+				Name:      "event",
+			},
+		},
+	}, "1")
+	if err != nil {
+		t.Fatalf("Replace returned error: %v", err)
+	}
+
+	queue, ok := store.ReflectorStore.(cache.Queue)
+	if !ok {
+		t.Fatal("DeltaFIFO store does not implement cache.Queue")
+	}
+
+	popped := make(chan struct{}, 1)
+	done := make(chan error, 1)
+	go func() {
+		_, err := queue.Pop(func(interface{}, bool) error {
+			popped <- struct{}{}
+			return nil
+		})
+		done <- err
+	}()
+
+	select {
+	case <-popped:
+		t.Fatal("Replace added an item to the queue")
+	case <-time.After(50 * time.Millisecond):
+	}
+
+	queue.Close()
+	if err := <-done; !errors.Is(err, cache.ErrFIFOClosed) {
+		t.Fatalf("Pop returned error %v, want %v", err, cache.ErrFIFOClosed)
+	}
+}