🌱 Test cache reader waits for cache sync

We don't seem to have any test coverage of this at all, change that.

Author: alvaroaleman

pkg/cache/cache_test.go

@@ -24,6 +24,8 @@ import (
 	"slices"
 	"strconv"
 	"strings"
+	"testing"
+	"testing/synctest"
 	"time"
 
 	. "github.com/onsi/ginkgo/v2"
@@ -2588,3 +2590,70 @@ func cancelledCtx(ctx context.Context) context.Context {
 	cancel()
 	return cancelCtx
 }
+
+type fakeRESTMapper struct {
+	meta.RESTMapper
+}
+
+func (f *fakeRESTMapper) RESTMapping(gk schema.GroupKind, versions ...string) (*meta.RESTMapping, error) {
+	return &meta.RESTMapping{Scope: meta.RESTScopeNamespace}, nil
+}
+
+func TestReaderWaitsForCacheSync(t *testing.T) {
+	t.Parallel()
+	for _, readerFailOnMissingInformer := range []bool{true, false} {
+		t.Run(fmt.Sprintf("ReaderFailOnMissingInformer=%v", readerFailOnMissingInformer), func(t *testing.T) {
+			t.Parallel()
+			synctest.Test(t, func(t *testing.T) {
+				g := NewWithT(t)
+
+				fakeInformer := &controllertest.FakeInformer{Synced: false}
+				c, err := cache.New(&rest.Config{}, cache.Options{
+					ReaderFailOnMissingInformer: readerFailOnMissingInformer,
+					Mapper:                      &fakeRESTMapper{},
+					NewInformer: func(kcache.ListerWatcher, runtime.Object, time.Duration, kcache.Indexers) kcache.SharedIndexInformer {
+						return fakeInformer
+					},
+				})
+				g.Expect(err).NotTo(HaveOccurred())
+
+				ctx, cancel := context.WithCancel(t.Context())
+				defer cancel()
+				cacheDone := make(chan struct{})
+				go func() {
+					g.Expect(c.Start(ctx)).To(Succeed())
+					close(cacheDone)
+				}()
+				synctest.Wait() // Let the cache finish starting
+				_, err = c.GetInformer(ctx, &corev1.Service{}, cache.BlockUntilSynced(false))
+				g.Expect(err).ToNot(HaveOccurred())
+
+				listCtx, listCtxCancel := context.WithTimeout(ctx, time.Second)
+				defer listCtxCancel()
+				services := &corev1.ServiceList{}
+				err = c.List(listCtx, services)
+				g.Expect(err).To(HaveOccurred())
+				g.Expect(apierrors.IsTimeout(err)).To(BeTrue())
+
+				getCtx, getCtxCancel := context.WithTimeout(ctx, time.Second)
+				defer getCtxCancel()
+				err = c.Get(getCtx, client.ObjectKey{Name: "default", Namespace: "kubernetes"}, &corev1.Service{})
+				g.Expect(err).To(HaveOccurred())
+				g.Expect(apierrors.IsTimeout(err)).To(BeTrue())
+
+				fakeInformer.SyncedLock.Lock()
+				fakeInformer.Synced = true
+				fakeInformer.SyncedLock.Unlock()
+
+				g.Expect(c.List(ctx, services)).To(Succeed())
+
+				err = c.Get(getCtx, client.ObjectKey{Name: "default", Namespace: "kubernetes"}, &corev1.Service{})
+				g.Expect(err).To(HaveOccurred())
+				g.Expect(apierrors.IsNotFound(err)).To(BeTrue())
+
+				cancel()
+				<-cacheDone
+			})
+		})
+	}
+}

pkg/controller/controllertest/util.go

@@ -18,6 +18,7 @@ package controllertest
 
 import (
 	"context"
+	"sync"
 	"time"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -29,7 +30,8 @@ var _ cache.SharedIndexInformer = &FakeInformer{}
 // FakeInformer provides fake Informer functionality for testing.
 type FakeInformer struct {
 	// Synced is returned by the HasSynced functions to implement the Informer interface
-	Synced bool
+	Synced     bool
+	SyncedLock sync.Mutex
 
 	// RunCount is incremented each time RunInformersAndControllers is called
 	RunCount int
@@ -44,6 +46,9 @@ type fakeHandlerRegistration struct {
 
 // HasSynced implements cache.ResourceEventHandlerRegistration.
 func (f *fakeHandlerRegistration) HasSynced() bool {
+	f.informer.SyncedLock.Lock()
+	defer f.informer.SyncedLock.Unlock()
+
 	return f.informer.Synced
 }
 
@@ -54,7 +59,7 @@ func (f *FakeInformer) AddIndexers(indexers cache.Indexers) error {
 
 // GetIndexer does nothing.  TODO(community): Implement this.
 func (f *FakeInformer) GetIndexer() cache.Indexer {
-	return nil
+	return cache.NewIndexer(cache.DeletionHandlingMetaNamespaceKeyFunc, nil)
 }
 
 // Informer returns the fake Informer.
@@ -64,6 +69,9 @@ func (f *FakeInformer) Informer() cache.SharedIndexInformer {
 
 // HasSynced implements the Informer interface.  Returns f.Synced.
 func (f *FakeInformer) HasSynced() bool {
+	f.SyncedLock.Lock()
+	defer f.SyncedLock.Unlock()
+
 	return f.Synced
 }