add new cache.Options field to customize transform

Author: Alexander Zielenski

pkg/cache/cache.go

@@ -128,6 +128,14 @@ type Options struct {
 	// 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
+
+	// TransformFuncByObject is a map from GVKs to transformer functions which
+	// get applied when objects of the transformation are about to be committed
+	// to cache.
+	//
+	// This function is called both for new objects to enter the cache,
+	// 	and for updated objects.
+	TransformFuncByObject TransformFuncByObject
 }
 
 var defaultResyncTime = 10 * time.Hour
@@ -146,7 +154,11 @@ 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)
+	transformByObjectAndGVK, err := convertToTransformByKindAndGVK(opts.TransformFuncByObject, opts.Scheme)
+	if err != nil {
+		return nil, err
+	}
+	im := internal.NewInformersMap(config, opts.Scheme, opts.Mapper, *opts.Resync, opts.Namespace, selectorsByGVK, disableDeepCopyByGVK, transformByObjectAndGVK)
 	return &informerCache{InformersMap: im}, nil
 }
 
@@ -241,3 +253,15 @@ func convertToDisableDeepCopyByGVK(disableDeepCopyByObject DisableDeepCopyByObje
 	}
 	return disableDeepCopyByGVK, nil
 }
+
+type TransformFuncByObject map[client.Object]toolscache.TransformFunc
+
+func convertToTransformByKindAndGVK(t TransformFuncByObject, scheme *runtime.Scheme) (internal.TransformFuncByObject, error) {
+	result := internal.NewTransformFuncByObject()
+	for obj, transformation := range t {
+		if err := result.Set(obj, scheme, transformation); err != nil {
+			return nil, err
+		}
+	}
+	return result, nil
+}

pkg/cache/internal/deleg_map.go

@@ -52,11 +52,12 @@ func NewInformersMap(config *rest.Config,
 	namespace string,
 	selectors SelectorsByGVK,
 	disableDeepCopy DisableDeepCopyByGVK,
+	transformers TransformFuncByObject,
 ) *InformersMap {
 	return &InformersMap{
-		structured:   newStructuredInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy),
-		unstructured: newUnstructuredInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy),
-		metadata:     newMetadataInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy),
+		structured:   newStructuredInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, transformers.Get(runtimeObjectKindStructured)),
+		unstructured: newUnstructuredInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, transformers.Get(runtimeObjectKindUnstructured)),
+		metadata:     newMetadataInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, transformers.Get(runtimeObjectKindMetadata)),
 
 		Scheme: scheme,
 	}
@@ -108,18 +109,18 @@ func (m *InformersMap) Get(ctx context.Context, gvk schema.GroupVersionKind, obj
 
 // newStructuredInformersMap creates a new InformersMap for structured objects.
 func newStructuredInformersMap(config *rest.Config, scheme *runtime.Scheme, mapper meta.RESTMapper, resync time.Duration,
-	namespace string, selectors SelectorsByGVK, disableDeepCopy DisableDeepCopyByGVK) *specificInformersMap {
-	return newSpecificInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, createStructuredListWatch)
+	namespace string, selectors SelectorsByGVK, disableDeepCopy DisableDeepCopyByGVK, transformers TransformFuncByGVK) *specificInformersMap {
+	return newSpecificInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, transformers, createStructuredListWatch)
 }
 
 // newUnstructuredInformersMap creates a new InformersMap for unstructured objects.
 func newUnstructuredInformersMap(config *rest.Config, scheme *runtime.Scheme, mapper meta.RESTMapper, resync time.Duration,
-	namespace string, selectors SelectorsByGVK, disableDeepCopy DisableDeepCopyByGVK) *specificInformersMap {
-	return newSpecificInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, createUnstructuredListWatch)
+	namespace string, selectors SelectorsByGVK, disableDeepCopy DisableDeepCopyByGVK, transformers TransformFuncByGVK) *specificInformersMap {
+	return newSpecificInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, transformers, createUnstructuredListWatch)
 }
 
 // newMetadataInformersMap creates a new InformersMap for metadata-only objects.
 func newMetadataInformersMap(config *rest.Config, scheme *runtime.Scheme, mapper meta.RESTMapper, resync time.Duration,
-	namespace string, selectors SelectorsByGVK, disableDeepCopy DisableDeepCopyByGVK) *specificInformersMap {
-	return newSpecificInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, createMetadataListWatch)
+	namespace string, selectors SelectorsByGVK, disableDeepCopy DisableDeepCopyByGVK, transformers TransformFuncByGVK) *specificInformersMap {
+	return newSpecificInformersMap(config, scheme, mapper, resync, namespace, selectors, disableDeepCopy, transformers, createMetadataListWatch)
 }

pkg/cache/internal/informers_map.go

@@ -54,7 +54,9 @@ func newSpecificInformersMap(config *rest.Config,
 	namespace string,
 	selectors SelectorsByGVK,
 	disableDeepCopy DisableDeepCopyByGVK,
-	createListWatcher createListWatcherFunc) *specificInformersMap {
+	transformers TransformFuncByGVK,
+	createListWatcher createListWatcherFunc,
+) *specificInformersMap {
 	ip := &specificInformersMap{
 		config:            config,
 		Scheme:            scheme,
@@ -135,6 +137,9 @@ type specificInformersMap struct {
 
 	// disableDeepCopy indicates not to deep copy objects during get or list objects.
 	disableDeepCopy DisableDeepCopyByGVK
+
+	// transform funcs are applied to objects before they are committed to the cache
+	transformers TransformFuncByGVK
 }
 
 // Start calls Run on each of the informers and sets started to true.  Blocks on the context.
@@ -227,6 +232,10 @@ func (ip *specificInformersMap) addInformerToMap(gvk schema.GroupVersionKind, ob
 	ni := cache.NewSharedIndexInformer(lw, obj, resyncPeriod(ip.resync)(), cache.Indexers{
 		cache.NamespaceIndex: cache.MetaNamespaceIndexFunc,
 	})
+
+	// Check to see if there is a transformer for this gvk
+	ni.SetTransform(ip.transformers.Get(gvk))
+
 	rm, err := ip.mapper.RESTMapping(gvk.GroupKind(), gvk.Version)
 	if err != nil {
 		return nil, false, err

pkg/cache/internal/transformers.go

@@ -0,0 +1,72 @@
+package internal
+
+import (
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/tools/cache"
+	"sigs.k8s.io/controller-runtime/pkg/client/apiutil"
+)
+
+type runtimeObjectKind int
+
+const (
+	// prefixed names since there are packages with these names that conflict
+	runtimeObjectKindStructured runtimeObjectKind = iota
+	runtimeObjectKindUnstructured
+	runtimeObjectKindMetadata
+)
+
+func runtimeObjectKindForObject(obj runtime.Object) runtimeObjectKind {
+	switch obj.(type) {
+	case *unstructured.Unstructured:
+		return runtimeObjectKindUnstructured
+	case *unstructured.UnstructuredList:
+		return runtimeObjectKindUnstructured
+	case *metav1.PartialObjectMetadata:
+		return runtimeObjectKindMetadata
+	case *metav1.PartialObjectMetadataList:
+		return runtimeObjectKindMetadata
+	default:
+		return runtimeObjectKindStructured
+	}
+}
+
+type TransformFuncByObject map[runtimeObjectKind]map[schema.GroupVersionKind]cache.TransformFunc
+type TransformFuncByGVK map[schema.GroupVersionKind]cache.TransformFunc
+
+func NewTransformFuncByObject() TransformFuncByObject {
+	return TransformFuncByObject{}
+}
+
+func (t TransformFuncByObject) Set(obj runtime.Object, scheme *runtime.Scheme, transformer cache.TransformFunc) error {
+	kind := runtimeObjectKindForObject(obj)
+	existing, ok := t[kind]
+	if !ok {
+		existing = TransformFuncByGVK{}
+		t[kind] = existing
+	}
+
+	gvk, err := apiutil.GVKForObject(obj, nil)
+	if err != nil {
+		return err
+	}
+
+	existing[gvk] = transformer
+	return nil
+}
+
+func (t TransformFuncByObject) Get(kind runtimeObjectKind) TransformFuncByGVK {
+	if val, ok := t[kind]; ok {
+		return val
+	}
+	return nil
+}
+
+func (t TransformFuncByGVK) Get(gvk schema.GroupVersionKind) cache.TransformFunc {
+	if val, ok := t[gvk]; ok {
+		return val
+	}
+	return nil
+}