Allow config to accept a Transformer

staging/src/k8s.io/apiserver/pkg/storage/storagebackend/config.go

@@ -16,7 +16,10 @@ limitations under the License.
 
 package storagebackend
 
-import "k8s.io/apimachinery/pkg/runtime"
+import (
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apiserver/pkg/storage/value"
+)
 
 const (
 	StorageTypeUnset = ""
@@ -45,6 +48,8 @@ type Config struct {
 
 	Codec  runtime.Codec
 	Copier runtime.ObjectCopier
+	// Transformer allows the value to be transformed prior to persisting into etcd.
+	Transformer value.Transformer
 }
 
 func NewDefaultConfig(prefix string, copier runtime.ObjectCopier, codec runtime.Codec) *Config {

staging/src/k8s.io/apiserver/pkg/storage/storagebackend/factory/etcd3.go

@@ -17,14 +17,14 @@ limitations under the License.
 package factory
 
 import (
+	"github.com/coreos/etcd/clientv3"
+	"github.com/coreos/etcd/pkg/transport"
+	"golang.org/x/net/context"
+
 	"k8s.io/apiserver/pkg/storage"
 	"k8s.io/apiserver/pkg/storage/etcd3"
 	"k8s.io/apiserver/pkg/storage/storagebackend"
 	"k8s.io/apiserver/pkg/storage/value"
-
-	"github.com/coreos/etcd/clientv3"
-	"github.com/coreos/etcd/pkg/transport"
-	"golang.org/x/net/context"
 )
 
 func newETCD3Storage(c storagebackend.Config) (storage.Interface, DestroyFunc, error) {
@@ -56,8 +56,12 @@ func newETCD3Storage(c storagebackend.Config) (storage.Interface, DestroyFunc, e
 		cancel()
 		client.Close()
 	}
+	transformer := c.Transformer
+	if transformer == nil {
+		transformer = value.IdentityTransformer
+	}
 	if c.Quorum {
-		return etcd3.New(client, c.Codec, c.Prefix, value.IdentityTransformer), destroyFunc, nil
+		return etcd3.New(client, c.Codec, c.Prefix, transformer), destroyFunc, nil
 	}
-	return etcd3.NewWithNoQuorumRead(client, c.Codec, c.Prefix, value.IdentityTransformer), destroyFunc, nil
+	return etcd3.NewWithNoQuorumRead(client, c.Codec, c.Prefix, transformer), destroyFunc, nil
 }