kubernetes/kops · error

error encoding %T

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.

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
• building node patch
• converting kubeconfig to yaml
• error building annotation patch
• error building node patch

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

Appendix: 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)