kubernetes/kops · error

error encoding %T: %v

Error message

error encoding %T: %v

What it means

k8scodecs.ToVersionedYaml encodes a runtime.Object using a k8s.io/apimachinery serializer. If the universal encoder's Encode fails — typically because the object's GVK is unknown to the scheme, the object is nil or of an unregistered type — the error is wrapped and returned. It reports the concrete Go type that could not be encoded.

Source

Thrown at pkg/k8scodecs/codecs.go:56

	metav1.AddToGroupVersion(Scheme, schema.GroupVersion{Version: "v1"})
	corev1.AddToScheme(Scheme)
}

func encoder() runtime.Encoder {
	yaml, ok := runtime.SerializerInfoForMediaType(Codecs.SupportedMediaTypes(), "application/yaml")
	if !ok {
		klog.Fatalf("no YAML serializer registered")
	}
	gv := corev1.SchemeGroupVersion
	return Codecs.EncoderForVersion(yaml.Serializer, gv)
}

// ToVersionedYaml encodes the object to YAML
func ToVersionedYaml(obj runtime.Object) ([]byte, error) {
	var w bytes.Buffer
	err := encoder().Encode(obj, &w)
	if err != nil {
		return nil, fmt.Errorf("error encoding %T: %v", obj, err)
	}
	return w.Bytes(), nil
}

View on GitHub (pinned to 4c8573c808)

Solutions

1. Register the object's type in the codec scheme (AddKnownTypes for its group/version).
2. Ensure the object is non-nil and its TypeMeta (apiVersion/kind) is set or inferable from the scheme.
3. Pass the concrete registered API type (e.g. *v1.Cluster) rather than an unregistered wrapper.

Example fix

// before
yamlBytes, err := k8scodecs.ToVersionedYaml(myCustomStruct) // unregistered
// after
scheme.AddKnownTypes(v1.SchemeGroupVersion, &v1.MyType{})
var obj runtime.Object = &v1.MyType{...}
yamlBytes, err := k8scodecs.ToVersionedYaml(obj)

func encodable(obj runtime.Object, scheme *runtime.Scheme) bool {
	if obj == nil {
		return false
	}
	gvk, _, _ := scheme.ObjectKinds(obj)
	return len(gvk) > 0 // type registered in the scheme
}

yamlBytes, err := k8scodecs.ToVersionedYaml(obj)
if err != nil {
	return fmt.Errorf("cannot encode %T to yaml: %w", obj, err)
}

When it happens

Trigger: Calling ToVersionedYaml with a runtime.Object whose type is not registered in the scheme used by encoder(); passing a nil object; passing a type lacking TypeMeta/ObjectMeta required by the serializer.

Common situations: Encoding a custom or third-party resource type not added via Scheme.AddKnownTypes; refactoring that swapped in a plain struct for a registered API type; older serialized data decoded into the wrong type before re-encoding.

Related errors

• marshaling to yaml for %v: %w
• error building annotation patch: %v
• failed to parse objects: %w
• building node patch: %w
• error building node patch: %v

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/aa9deb73df3f60b6. Report an issue: GitHub.