Create a new method UnsafeConvertToVersion for faster convert

Only encode/decode will call this path, to allow us to optimize for
unsafe operations.

pkg/api/conversion_test.go

@@ -50,11 +50,11 @@ func BenchmarkPodConversion(b *testing.B) {
 	var result *api.Pod
 	for i := 0; i < b.N; i++ {
 		pod := &items[i%width]
-		versionedObj, err := scheme.ConvertToVersion(pod, *testapi.Default.GroupVersion())
+		versionedObj, err := scheme.UnsafeConvertToVersion(pod, *testapi.Default.GroupVersion())
 		if err != nil {
 			b.Fatalf("Conversion error: %v", err)
 		}
-		obj, err := scheme.ConvertToVersion(versionedObj, testapi.Default.InternalGroupVersion())
+		obj, err := scheme.UnsafeConvertToVersion(versionedObj, testapi.Default.InternalGroupVersion())
 		if err != nil {
 			b.Fatalf("Conversion error: %v", err)
 		}
@@ -76,11 +76,11 @@ func BenchmarkNodeConversion(b *testing.B) {
 	scheme := api.Scheme
 	var result *api.Node
 	for i := 0; i < b.N; i++ {
-		versionedObj, err := scheme.ConvertToVersion(&node, *testapi.Default.GroupVersion())
+		versionedObj, err := scheme.UnsafeConvertToVersion(&node, *testapi.Default.GroupVersion())
 		if err != nil {
 			b.Fatalf("Conversion error: %v", err)
 		}
-		obj, err := scheme.ConvertToVersion(versionedObj, testapi.Default.InternalGroupVersion())
+		obj, err := scheme.UnsafeConvertToVersion(versionedObj, testapi.Default.InternalGroupVersion())
 		if err != nil {
 			b.Fatalf("Conversion error: %v", err)
 		}
@@ -104,11 +104,11 @@ func BenchmarkReplicationControllerConversion(b *testing.B) {
 	scheme := api.Scheme
 	var result *api.ReplicationController
 	for i := 0; i < b.N; i++ {
-		versionedObj, err := scheme.ConvertToVersion(&replicationController, *testapi.Default.GroupVersion())
+		versionedObj, err := scheme.UnsafeConvertToVersion(&replicationController, *testapi.Default.GroupVersion())
 		if err != nil {
 			b.Fatalf("Conversion error: %v", err)
 		}
-		obj, err := scheme.ConvertToVersion(versionedObj, testapi.Default.InternalGroupVersion())
+		obj, err := scheme.UnsafeConvertToVersion(versionedObj, testapi.Default.InternalGroupVersion())
 		if err != nil {
 			b.Fatalf("Conversion error: %v", err)
 		}

pkg/runtime/helper.go

@@ -43,10 +43,31 @@ func (t objectTyperToTyper) ObjectKind(obj Object) (*unversioned.GroupVersionKin
 	return &gvk, unversionedType, nil
 }
 
+// ObjectTyperToTyper casts the old typer interface to the new typer interface
 func ObjectTyperToTyper(typer ObjectTyper) Typer {
 	return objectTyperToTyper{typer: typer}
 }
 
+// unsafeObjectConvertor implements ObjectConvertor using the unsafe conversion path.
+type unsafeObjectConvertor struct {
+	*Scheme
+}
+
+var _ ObjectConvertor = unsafeObjectConvertor{}
+
+// ConvertToVersion converts in to the provided outVersion without copying the input first, which
+// is only safe if the output object is not mutated or reused.
+func (c unsafeObjectConvertor) ConvertToVersion(in Object, outVersion unversioned.GroupVersion) (Object, error) {
+	return c.Scheme.UnsafeConvertToVersion(in, outVersion)
+}
+
+// UnsafeObjectConvertor performs object conversion without copying the object structure,
+// for use when the converted object will not be reused or mutated. Primarily for use within
+// versioned codecs, which use the external object for serialization but do not return it.
+func UnsafeObjectConvertor(scheme *Scheme) ObjectConvertor {
+	return unsafeObjectConvertor{scheme}
+}
+
 // fieldPtr puts the address of fieldName, which must be a member of v,
 // into dest, which must be an address of a variable to which this field's
 // address can be assigned.

pkg/runtime/scheme.go

@@ -523,11 +523,80 @@ func (s *Scheme) ConvertToVersion(in Object, outVersion unversioned.GroupVersion
 	return out, nil
 }
 
+// UnsafeConvertToVersion will convert in to the provided outVersion if such a conversion is possible,
+// but does not guarantee the output object does not share fields with the input object. It attempts to be as
+// efficient as possible when doing conversion.
+func (s *Scheme) UnsafeConvertToVersion(in Object, outVersion unversioned.GroupVersion) (Object, error) {
+	switch t := in.(type) {
+	case *Unknown:
+		t.APIVersion = outVersion.String()
+		return t, nil
+	case *Unstructured:
+		t.SetAPIVersion(outVersion.String())
+		return t, nil
+	case *UnstructuredList:
+		t.SetAPIVersion(outVersion.String())
+		return t, nil
+	}
+
+	// determine the incoming kinds with as few allocations as possible.
+	t := reflect.TypeOf(in)
+	if t.Kind() != reflect.Ptr {
+		return nil, fmt.Errorf("only pointer types may be converted: %v", t)
+	}
+	t = t.Elem()
+	if t.Kind() != reflect.Struct {
+		return nil, fmt.Errorf("only pointers to struct types may be converted: %v", t)
+	}
+	kinds, ok := s.typeToGVK[t]
+	if !ok || len(kinds) == 0 {
+		return nil, fmt.Errorf("%v is not a registered type and cannot be converted into version %q", t, outVersion)
+	}
+
+	// if the Go type is also registered to the destination kind, no conversion is necessary
+	for i := range kinds {
+		if kinds[i].Version == outVersion.Version && kinds[i].Group == outVersion.Group {
+			setTargetKind(in, kinds[i])
+			return in, nil
+		}
+	}
+
+	// type is unversioned, no conversion necessary
+	// it should be possible to avoid this allocation
+	if unversionedKind, ok := s.unversionedTypes[t]; ok {
+		kind := unversionedKind
+		outKind := outVersion.WithKind(kind.Kind)
+		setTargetKind(in, outKind)
+		return in, nil
+	}
+
+	// allocate a new object as the target using the target kind
+	// TODO: this should look in the target group version and find the first kind that matches, rather than the
+	//   first kind registered in typeToGVK
+	kind := kinds[0]
+	kind.Version = outVersion.Version
+	kind.Group = outVersion.Group
+	out, err := s.New(kind)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO: try to avoid the allocations here - in fast paths we are not likely to need these flags or meta
+	flags, meta := s.converter.DefaultMeta(t)
+	if err := s.converter.Convert(in, out, flags, meta); err != nil {
+		return nil, err
+	}
+
+	setTargetKind(out, kind)
+	return out, nil
+}
+
 // generateConvertMeta constructs the meta value we pass to Convert.
 func (s *Scheme) generateConvertMeta(srcGroupVersion, destGroupVersion unversioned.GroupVersion, in interface{}) (conversion.FieldMatchingFlags, *conversion.Meta) {
 	return s.converter.DefaultMeta(reflect.TypeOf(in))
 }
 
+// setTargetVersion is deprecated and should be replaced by use of setTargetKind
 func setTargetVersion(obj Object, raw *Scheme, gv unversioned.GroupVersion) {
 	if gv.Version == APIVersionInternal {
 		// internal is a special case
@@ -537,3 +606,14 @@ func setTargetVersion(obj Object, raw *Scheme, gv unversioned.GroupVersion) {
 	gvk, _ := raw.ObjectKind(obj)
 	obj.GetObjectKind().SetGroupVersionKind(unversioned.GroupVersionKind{Group: gv.Group, Version: gv.Version, Kind: gvk.Kind})
 }
+
+// setTargetKind sets the kind on an object, taking into account whether the target kind is the internal version.
+func setTargetKind(obj Object, kind unversioned.GroupVersionKind) {
+	if kind.Version == APIVersionInternal {
+		// internal is a special case
+		// TODO: look at removing the need to special case this
+		obj.GetObjectKind().SetGroupVersionKind(unversioned.GroupVersionKind{})
+		return
+	}
+	obj.GetObjectKind().SetGroupVersionKind(kind)
+}

pkg/runtime/serializer/versioning/versioning.go

@@ -71,7 +71,7 @@ func NewCodecForScheme(
 	encodeVersion []unversioned.GroupVersion,
 	decodeVersion []unversioned.GroupVersion,
 ) runtime.Codec {
-	return NewCodec(encoder, decoder, scheme, scheme, scheme, runtime.ObjectTyperToTyper(scheme), encodeVersion, decodeVersion)
+	return NewCodec(encoder, decoder, runtime.UnsafeObjectConvertor(scheme), scheme, scheme, runtime.ObjectTyperToTyper(scheme), encodeVersion, decodeVersion)
 }
 
 // NewCodec takes objects in their internal versions and converts them to external versions before
@@ -263,21 +263,19 @@ func (c *codec) EncodeToStream(obj runtime.Object, w io.Writer, overrides ...unv
 	}
 
 	// Perform a conversion if necessary
-	if gvk.GroupVersion() != targetGV {
-		out, err := c.convertor.ConvertToVersion(obj, targetGV)
-		if err != nil {
-			if ok {
-				return err
-			}
-		} else {
-			obj = out
-		}
-	}
-
 	objectKind := obj.GetObjectKind()
 	old := objectKind.GroupVersionKind()
-	objectKind.SetGroupVersionKind(unversioned.GroupVersionKind{Group: targetGV.Group, Version: targetGV.Version, Kind: gvk.Kind})
+	out, err := c.convertor.ConvertToVersion(obj, targetGV)
+	if err != nil {
+		if ok {
+			return err
+		}
+	} else {
+		obj = out
+	}
+	// Conversion is responsible for setting the proper group, version, and kind onto the outgoing object
 	err = c.encoder.EncodeToStream(obj, w, overrides...)
+	// restore the old GVK, in case conversion returned the same object
 	objectKind.SetGroupVersionKind(old)
 	return err
 }