Merge pull request #3127 from k8s-infra-cherrypick-robot/cherry-pick-3126-to-release-0.20

[release-0.20] 🐛 fix: cache should list out of global cache when present and necessary

Author: k8s-ci-robot

pkg/cache/cache_test.go

@@ -130,16 +130,16 @@ var _ = Describe("Informer Cache with ReaderFailOnMissingInformer", func() {
 var _ = Describe("Multi-Namespace Informer Cache", func() {
 	CacheTest(cache.New, cache.Options{
 		DefaultNamespaces: map[string]cache.Config{
-			testNamespaceOne: {},
-			testNamespaceTwo: {},
-			"default":        {},
+			cache.AllNamespaces: {FieldSelector: fields.OneTermEqualSelector("metadata.namespace", testNamespaceOne)},
+			testNamespaceTwo:    {},
+			"default":           {},
 		},
 	})
 	NonBlockingGetTest(cache.New, cache.Options{
 		DefaultNamespaces: map[string]cache.Config{
-			testNamespaceOne: {},
-			testNamespaceTwo: {},
-			"default":        {},
+			cache.AllNamespaces: {FieldSelector: fields.OneTermEqualSelector("metadata.namespace", testNamespaceOne)},
+			testNamespaceTwo:    {},
+			"default":           {},
 		},
 	})
 })

pkg/cache/multi_namespace_cache.go

@@ -262,6 +262,9 @@ func (c *multiNamespaceCache) List(ctx context.Context, list client.ObjectList,
 	if listOpts.Namespace != corev1.NamespaceAll {
 		cache, ok := c.namespaceToCache[listOpts.Namespace]
 		if !ok {
+			if global, hasGlobal := c.namespaceToCache[AllNamespaces]; hasGlobal {
+				return global.List(ctx, list, opts...)
+			}
 			return fmt.Errorf("unable to list: %v because of unknown namespace for the cache", listOpts.Namespace)
 		}
 		return cache.List(ctx, list, opts...)