Add UnsafeDisableCacheDeepCopy as list option to avoid deep copy duri…

…ng list (#1274)

Signed-off-by: Siyu Wang <FillZpp.pub@gmail.com>

pkg/cache/cache.go

@@ -113,6 +113,12 @@ type Options struct {
 	// [1] https://pkg.go.dev/k8s.io/apimachinery/pkg/fields#Selector
 	// [2] https://pkg.go.dev/k8s.io/apimachinery/pkg/fields#Set
 	SelectorsByObject SelectorsByObject
+
+	// UnsafeDisableDeepCopyByObject indicates not to deep copy objects during get or
+	// list objects per GVK at the specified object.
+	// Be very careful with this, when enabled you must DeepCopy any object before mutating it,
+	// otherwise you will mutate the object in the cache.
+	UnsafeDisableDeepCopyByObject DisableDeepCopyByObject
 }
 
 var defaultResyncTime = 10 * time.Hour
@@ -127,7 +133,11 @@ func New(config *rest.Config, opts Options) (Cache, error) {
 	if err != nil {
 		return nil, err
 	}
-	im := internal.NewInformersMap(config, opts.Scheme, opts.Mapper, *opts.Resync, opts.Namespace, selectorsByGVK)
+	disableDeepCopyByGVK, err := convertToDisableDeepCopyByGVK(opts.UnsafeDisableDeepCopyByObject, opts.Scheme)
+	if err != nil {
+		return nil, err
+	}
+	im := internal.NewInformersMap(config, opts.Scheme, opts.Mapper, *opts.Resync, opts.Namespace, selectorsByGVK, disableDeepCopyByGVK)
 	return &informerCache{InformersMap: im}, nil
 }
 
@@ -136,6 +146,8 @@ func New(config *rest.Config, opts Options) (Cache, error) {
 // SelectorsByObject
 // WARNING: if SelectorsByObject is specified. filtered out resources are not
 //          returned.
+// WARNING: if UnsafeDisableDeepCopy is enabled, you must DeepCopy any object
+//          returned from cache get/list before mutating it.
 func BuilderWithOptions(options Options) NewCacheFunc {
 	return func(config *rest.Config, opts Options) (Cache, error) {
 		if opts.Scheme == nil {
@@ -151,6 +163,7 @@ func BuilderWithOptions(options Options) NewCacheFunc {
 			opts.Namespace = options.Namespace
 		}
 		opts.SelectorsByObject = options.SelectorsByObject
+		opts.UnsafeDisableDeepCopyByObject = options.UnsafeDisableDeepCopyByObject
 		return New(config, opts)
 	}
 }
@@ -189,3 +202,30 @@ func convertToSelectorsByGVK(selectorsByObject SelectorsByObject, scheme *runtim
 	}
 	return selectorsByGVK, nil
 }
+
+// DisableDeepCopyByObject associate a client.Object's GVK to disable DeepCopy during get or list from cache.
+type DisableDeepCopyByObject map[client.Object]bool
+
+var _ client.Object = &ObjectAll{}
+
+// ObjectAll is the argument to represent all objects' types.
+type ObjectAll struct {
+	client.Object
+}
+
+func convertToDisableDeepCopyByGVK(disableDeepCopyByObject DisableDeepCopyByObject, scheme *runtime.Scheme) (internal.DisableDeepCopyByGVK, error) {
+	disableDeepCopyByGVK := internal.DisableDeepCopyByGVK{}
+	for obj, disable := range disableDeepCopyByObject {
+		switch obj.(type) {
+		case ObjectAll, *ObjectAll:
+			disableDeepCopyByGVK[internal.GroupVersionKindAll] = disable
+		default:
+			gvk, err := apiutil.GVKForObject(obj, scheme)
+			if err != nil {
+				return nil, err
+			}
+			disableDeepCopyByGVK[gvk] = disable
+		}
+	}
+	return disableDeepCopyByGVK, nil
+}