✨ Take context when getting informer

Passing the context down to the `ip.InformersMap.Get()` makes it possible
to handle scenarios where the cache takes too long to sync or will
never sync.

Author: djzager

pkg/cache/cache_test.go

@@ -261,6 +261,20 @@ func CacheTest(createCacheFunc func(config *rest.Config, opts cache.Options) (ca
 					err := informerCache.Get(context.Background(), svcKey, svc)
 					Expect(err).To(HaveOccurred())
 				})
+
+				It("should return an error when context is cancelled", func() {
+					By("creating a context and cancelling it")
+					ctx, cancel := context.WithCancel(context.Background())
+					cancel()
+
+					By("listing pods in test-namespace-1 with a cancelled context")
+					listObj := &kcorev1.PodList{}
+					err := informerCache.List(ctx, listObj, client.InNamespace(testNamespaceOne))
+
+					By("verifying that an error is returned")
+					Expect(err).To(HaveOccurred())
+					Expect(errors.IsTimeout(err)).To(BeTrue())
+				})
 			})
 			Context("with unstructured objects", func() {
 				It("should be able to list objects that haven't been watched previously", func() {

pkg/cache/informer_cache.go

@@ -57,7 +57,7 @@ func (ip *informerCache) Get(ctx context.Context, key client.ObjectKey, out runt
 		return err
 	}
 
-	started, cache, err := ip.InformersMap.Get(gvk, out)
+	started, cache, err := ip.InformersMap.Get(ctx, gvk, out)
 	if err != nil {
 		return err
 	}
@@ -76,7 +76,7 @@ func (ip *informerCache) List(ctx context.Context, out runtime.Object, opts ...c
 		return err
 	}
 
-	started, cache, err := ip.InformersMap.Get(*gvk, cacheTypeObj)
+	started, cache, err := ip.InformersMap.Get(ctx, *gvk, cacheTypeObj)
 	if err != nil {
 		return err
 	}
@@ -128,7 +128,6 @@ func (ip *informerCache) objectTypeForListObject(list runtime.Object) (*schema.G
 	}
 
 	return &gvk, cacheTypeObj, nil
-
 }
 
 // GetInformerForKind returns the informer for the GroupVersionKind
@@ -138,7 +137,10 @@ func (ip *informerCache) GetInformerForKind(gvk schema.GroupVersionKind) (Inform
 	if err != nil {
 		return nil, err
 	}
-	_, i, err := ip.InformersMap.Get(gvk, obj)
+
+	// TODO(djzager): before a context can be passed down, the Informers interface
+	// must be updated to accept a context when getting an informer
+	_, i, err := ip.InformersMap.Get(context.TODO(), gvk, obj)
 	if err != nil {
 		return nil, err
 	}
@@ -151,7 +153,10 @@ func (ip *informerCache) GetInformer(obj runtime.Object) (Informer, error) {
 	if err != nil {
 		return nil, err
 	}
-	_, i, err := ip.InformersMap.Get(gvk, obj)
+
+	// TODO(djzager): before a context can be passed down, the Informers interface
+	// must be updated to accept a context when getting an informer
+	_, i, err := ip.InformersMap.Get(context.TODO(), gvk, obj)
 	if err != nil {
 		return nil, err
 	}

pkg/cache/internal/deleg_map.go

@@ -17,6 +17,7 @@ limitations under the License.
 package internal
 
 import (
+	"context"
 	"time"
 
 	"k8s.io/apimachinery/pkg/api/meta"
@@ -79,16 +80,16 @@ func (m *InformersMap) WaitForCacheSync(stop <-chan struct{}) bool {
 
 // Get will create a new Informer and add it to the map of InformersMap if none exists.  Returns
 // the Informer from the map.
-func (m *InformersMap) Get(gvk schema.GroupVersionKind, obj runtime.Object) (bool, *MapEntry, error) {
+func (m *InformersMap) Get(ctx context.Context, gvk schema.GroupVersionKind, obj runtime.Object) (bool, *MapEntry, error) {
 	_, isUnstructured := obj.(*unstructured.Unstructured)
 	_, isUnstructuredList := obj.(*unstructured.UnstructuredList)
 	isUnstructured = isUnstructured || isUnstructuredList
 
 	if isUnstructured {
-		return m.unstructured.Get(gvk, obj)
+		return m.unstructured.Get(ctx, gvk, obj)
 	}
 
-	return m.structured.Get(gvk, obj)
+	return m.structured.Get(ctx, gvk, obj)
 }
 
 // newStructuredInformersMap creates a new InformersMap for structured objects.

pkg/cache/internal/informers_map.go

@@ -17,11 +17,13 @@ limitations under the License.
 package internal
 
 import (
+	"context"
 	"fmt"
 	"math/rand"
 	"sync"
 	"time"
 
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -163,7 +165,7 @@ func (ip *specificInformersMap) HasSyncedFuncs() []cache.InformerSynced {
 
 // Get will create a new Informer and add it to the map of specificInformersMap if none exists.  Returns
 // the Informer from the map.
-func (ip *specificInformersMap) Get(gvk schema.GroupVersionKind, obj runtime.Object) (bool, *MapEntry, error) {
+func (ip *specificInformersMap) Get(ctx context.Context, gvk schema.GroupVersionKind, obj runtime.Object) (bool, *MapEntry, error) {
 	// Return the informer if it is found
 	i, started, ok := func() (*MapEntry, bool, bool) {
 		ip.mu.RLock()
@@ -181,8 +183,8 @@ func (ip *specificInformersMap) Get(gvk schema.GroupVersionKind, obj runtime.Obj
 
 	if started && !i.Informer.HasSynced() {
 		// Wait for it to sync before returning the Informer so that folks don't read from a stale cache.
-		if !cache.WaitForCacheSync(ip.stop, i.Informer.HasSynced) {
-			return started, nil, fmt.Errorf("failed waiting for %T Informer to sync", obj)
+		if !cache.WaitForCacheSync(ctx.Done(), i.Informer.HasSynced) {
+			return started, nil, apierrors.NewTimeoutError(fmt.Sprintf("failed waiting for %T Informer to sync", obj), 0)
 		}
 	}