refactor etcd store conditional delete

staging/src/k8s.io/apiserver/pkg/storage/etcd3/store.go

@@ -271,13 +271,15 @@ func (s *store) Delete(
 	if err != nil {
 		return fmt.Errorf("unable to convert output object to pointer: %v", err)
 	}
-	return s.conditionalDelete(ctx, preparedKey, out, v, preconditions, validateDeletion, cachedExistingObject)
+
+	skipTransformDecode := false
+	return s.conditionalDelete(ctx, preparedKey, out, v, preconditions, validateDeletion, cachedExistingObject, skipTransformDecode)
 }
 
 func (s *store) conditionalDelete(
 	ctx context.Context, key string, out runtime.Object, v reflect.Value, preconditions *storage.Preconditions,
-	validateDeletion storage.ValidateObjectFunc, cachedExistingObject runtime.Object) error {
+	validateDeletion storage.ValidateObjectFunc, cachedExistingObject runtime.Object, skipTransformDecode bool) error {
-	getCurrentState := s.getCurrentState(ctx, key, v, false)
+	getCurrentState := s.getCurrentState(ctx, key, v, false, skipTransformDecode)
 
 	var origState *objState
 	var err error
@@ -361,7 +363,7 @@ func (s *store) conditionalDelete(
 		if !txnResp.Succeeded {
 			getResp := (*clientv3.GetResponse)(txnResp.Responses[0].GetResponseRange())
 			klog.V(4).Infof("deletion of %s failed because of a conflict, going to retry", key)
-			origState, err = s.getState(ctx, getResp, key, v, false)
+			origState, err = s.getState(ctx, getResp, key, v, false, skipTransformDecode)
 			if err != nil {
 				return err
 			}
@@ -376,11 +378,13 @@ func (s *store) conditionalDelete(
 		if deleteResp.Header == nil {
 			return errors.New("invalid DeleteRange response - nil header")
 		}
+		if !skipTransformDecode {
 			err = decode(s.codec, s.versioner, origState.data, out, deleteResp.Header.Revision)
 			if err != nil {
 				recordDecodeError(s.groupResourceString, key)
 				return err
 			}
+		}
 		return nil
 	}
 }
@@ -405,7 +409,8 @@ func (s *store) GuaranteedUpdate(
 		return fmt.Errorf("unable to convert output object to pointer: %v", err)
 	}
 
-	getCurrentState := s.getCurrentState(ctx, preparedKey, v, ignoreNotFound)
+	skipTransformDecode := false
+	getCurrentState := s.getCurrentState(ctx, preparedKey, v, ignoreNotFound, skipTransformDecode)
 
 	var origState *objState
 	var origStateIsCurrent bool
@@ -531,7 +536,8 @@ func (s *store) GuaranteedUpdate(
 		if !txnResp.Succeeded {
 			getResp := (*clientv3.GetResponse)(txnResp.Responses[0].GetResponseRange())
 			klog.V(4).Infof("GuaranteedUpdate of %s failed because of a conflict, going to retry", preparedKey)
-			origState, err = s.getState(ctx, getResp, preparedKey, v, ignoreNotFound)
+			skipTransformDecode := false
+			origState, err = s.getState(ctx, getResp, preparedKey, v, ignoreNotFound, skipTransformDecode)
 			if err != nil {
 				return err
 			}
@@ -878,7 +884,7 @@ func (s *store) watchContext(ctx context.Context) context.Context {
 	return clientv3.WithRequireLeader(ctx)
 }
 
-func (s *store) getCurrentState(ctx context.Context, key string, v reflect.Value, ignoreNotFound bool) func() (*objState, error) {
+func (s *store) getCurrentState(ctx context.Context, key string, v reflect.Value, ignoreNotFound bool, skipTransformDecode bool) func() (*objState, error) {
 	return func() (*objState, error) {
 		startTime := time.Now()
 		getResp, err := s.client.KV.Get(ctx, key)
@@ -886,11 +892,17 @@ func (s *store) getCurrentState(ctx context.Context, key string, v reflect.Value
 		if err != nil {
 			return nil, err
 		}
-		return s.getState(ctx, getResp, key, v, ignoreNotFound)
+		return s.getState(ctx, getResp, key, v, ignoreNotFound, skipTransformDecode)
 	}
 }
 
-func (s *store) getState(ctx context.Context, getResp *clientv3.GetResponse, key string, v reflect.Value, ignoreNotFound bool) (*objState, error) {
+// getState constructs a new objState from the given response from the storage.
+// skipTransformDecode: if true, the function will neither transform the data
+// from the storage nor decode it into an object; otherwise, data from the
+// storage will be transformed and decoded.
+// NOTE: when skipTransformDecode is true, the 'data', and the 'obj' fields
+// of the objState will be nil, and 'stale' will be set to true.
+func (s *store) getState(ctx context.Context, getResp *clientv3.GetResponse, key string, v reflect.Value, ignoreNotFound bool, skipTransformDecode bool) (*objState, error) {
 	state := &objState{
 		meta: &storage.ResponseMeta{},
 	}
@@ -909,14 +921,24 @@ func (s *store) getState(ctx context.Context, getResp *clientv3.GetResponse, key
 			return nil, err
 		}
 	} else {
+		state.rev = getResp.Kvs[0].ModRevision
+		state.meta.ResourceVersion = uint64(state.rev)
+
+		if skipTransformDecode {
+			// be explicit that we don't have the object
+			state.obj = nil
+			state.stale = true // this seems a more sane value here
+			return state, nil
+		}
+
 		data, stale, err := s.transformer.TransformFromStorage(ctx, getResp.Kvs[0].Value, authenticatedDataString(key))
 		if err != nil {
 			return nil, storage.NewInternalError(err.Error())
 		}
-		state.rev = getResp.Kvs[0].ModRevision
+
-		state.meta.ResourceVersion = uint64(state.rev)
 		state.data = data
 		state.stale = stale
+
 		if err := decode(s.codec, s.versioner, state.data, state.obj, state.rev); err != nil {
 			recordDecodeError(s.groupResourceString, key)
 			return nil, err

staging/src/k8s.io/apiserver/pkg/storage/interfaces.go

@@ -108,6 +108,8 @@ type UpdateFunc func(input runtime.Object, res ResponseMeta) (output runtime.Obj
 // ValidateObjectFunc is a function to act on a given object. An error may be returned
 // if the hook cannot be completed. The function may NOT transform the provided
 // object.
+// NOTE: the object in obj may be nil if it cannot be read from the
+// storage, due to transformation or decode error.
 type ValidateObjectFunc func(ctx context.Context, obj runtime.Object) error
 
 // ValidateAllObjectFunc is a "admit everything" instance of ValidateObjectFunc.

staging/src/k8s.io/apiserver/pkg/storage/interfaces_test.go

@@ -0,0 +1,39 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package storage
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+func TestPreconditionsCheckWithNilObject(t *testing.T) {
+	p := &Preconditions{}
+	err := p.Check("foo", nil)
+	if err == nil {
+		t.Fatalf("expected an error")
+	}
+
+	var internalErr InternalError
+	if !errors.As(err, &internalErr) {
+		t.Fatalf("expected error to be of type: %T, but got: %#v", InternalError{}, err)
+	}
+	if want := "can't enforce preconditions"; !strings.Contains(internalErr.Error(), want) {
+		t.Errorf("expected error to contain %q", want)
+	}
+}