pkg/resource: make patching applicator consistent and deprecate update applicator

Signed-off-by: Dr. Stefan Schimanski <[email protected]>

Author: sttts

pkg/resource/api.go

@@ -18,12 +18,12 @@ package resource
 
 import (
 	"context"
-	"encoding/json"
 
 	corev1 "k8s.io/api/core/v1"
 	kerrors "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/types"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 
@@ -121,41 +121,54 @@ func NewAPIPatchingApplicator(c client.Client) *APIPatchingApplicator {
 // Apply changes to the supplied object. The object will be created if it does
 // not exist, or patched if it does. If the object does exist, it will only be
 // patched if the passed object has the same or an empty resource version.
-func (a *APIPatchingApplicator) Apply(ctx context.Context, o client.Object, ao ...ApplyOption) error {
-	m, ok := o.(metav1.Object)
-	if !ok {
-		return errors.New("cannot access object metadata")
+func (a *APIPatchingApplicator) Apply(ctx context.Context, obj client.Object, ao ...ApplyOption) error {
+	if obj.GetName() == "" && obj.GetGenerateName() != "" {
+		return errors.Wrap(a.client.Create(ctx, obj), "cannot create object")
 	}
 
-	if m.GetName() == "" && m.GetGenerateName() != "" {
-		return errors.Wrap(a.client.Create(ctx, o), "cannot create object")
-	}
-
-	desired := o.DeepCopyObject()
-
-	err := a.client.Get(ctx, types.NamespacedName{Name: m.GetName(), Namespace: m.GetNamespace()}, o)
+	current := obj.DeepCopyObject().(client.Object)
+	err := a.client.Get(ctx, types.NamespacedName{Name: obj.GetName(), Namespace: obj.GetNamespace()}, current)
 	if kerrors.IsNotFound(err) {
 		// TODO(negz): Apply ApplyOptions here too?
-		return errors.Wrap(a.client.Create(ctx, o), "cannot create object")
+		return errors.Wrap(a.client.Create(ctx, obj), "cannot create object")
 	}
 	if err != nil {
 		return errors.Wrap(err, "cannot get object")
 	}
 
+	// Note: this check would ideally not be necessary if the Apply signature
+	// had a current object that we could us for the diff. But we have no
+	// current and for consistency of the patch it matter that the object we get
+	// above is the one that was originally used.
+	if obj.GetResourceVersion() != "" && obj.GetResourceVersion() != current.GetResourceVersion() {
+		gvr, err := groupResource(a.client, obj)
+		if err != nil {
+			return err
+		}
+		return kerrors.NewConflict(gvr, current.GetName(), errors.New("resource version does not match"))
+	}
+
 	for _, fn := range ao {
-		if err := fn(ctx, o, desired); err != nil {
+		if err := fn(ctx, current, obj); err != nil {
 			return err
 		}
 	}
 
 	// TODO(negz): Allow callers to override the kind of patch used.
-	return errors.Wrap(a.client.Patch(ctx, o, &patch{desired}), "cannot patch object")
+	return errors.Wrap(a.client.Patch(ctx, obj, client.MergeFromWithOptions(current, client.MergeFromWithOptimisticLock{})), "cannot patch object")
 }
 
-type patch struct{ from runtime.Object }
-
-func (p *patch) Type() types.PatchType                { return types.MergePatchType }
-func (p *patch) Data(_ client.Object) ([]byte, error) { return json.Marshal(p.from) }
+func groupResource(c client.Client, o client.Object) (schema.GroupResource, error) {
+	gvk, err := c.GroupVersionKindFor(o)
+	if err != nil {
+		return schema.GroupResource{}, errors.Wrapf(err, "cannot determine group version kind of %T", o)
+	}
+	m, err := c.RESTMapper().RESTMapping(gvk.GroupKind(), gvk.Version)
+	if err != nil {
+		return schema.GroupResource{}, errors.Wrapf(err, "cannot determine group resource of %v", gvk)
+	}
+	return m.Resource.GroupResource(), nil
+}
 
 // An APIUpdatingApplicator applies changes to an object by either creating or
 // updating it in a Kubernetes API server.
@@ -165,6 +178,9 @@ type APIUpdatingApplicator struct {
 
 // NewAPIUpdatingApplicator returns an Applicator that applies changes to an
 // object by either creating or updating it in a Kubernetes API server.
+//
+// Deprecated: Use NewAPIPatchingApplicator instead. The updating applicator
+// can lead to data-loss if the Golang types in this process are not up-to-date.
 func NewAPIUpdatingApplicator(c client.Client) *APIUpdatingApplicator {
 	return &APIUpdatingApplicator{client: c}
 }

pkg/resource/resource.go

@@ -231,7 +231,8 @@ func IsConditionTrue(c xpv1.Condition) bool {
 	return c.Status == corev1.ConditionTrue
 }
 
-// An Applicator applies changes to an object.
+// An Applicator applies changes to an object. The passed object is expected to
+// be complete, i.e. not partial.
 type Applicator interface {
 	Apply(context.Context, client.Object, ...ApplyOption) error
 }