kubernetes/kops · error

error marshaling object: %v

Error message

error marshaling object: %v

What it means

writeConfig() failed while serializing the object before any write occurred: c.serialize(o) returned an error (itself wrapping encoder.Encode failures) and is re-wrapped as 'error marshaling object'. Called by Create, Update, create, and update.

Source

Thrown at pkg/client/simple/vfsclientset/commonvfs.go:137

	data, err := configPath.ReadFile(ctx)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, err
		}
		return nil, fmt.Errorf("error reading %s: %v", configPath, err)
	}

	object, _, err := kopscodecs.Decode(data, nil)
	if err != nil {
		return nil, fmt.Errorf("error parsing %s: %v", configPath, err)
	}
	return object, nil
}

func (c *VFSClientBase) writeConfig(ctx context.Context, cluster *kops.Cluster, configPath vfs.Path, o runtime.Object, writeOptions ...vfs.WriteOption) error {
	data, err := c.serialize(o)
	if err != nil {
		return fmt.Errorf("error marshaling object: %v", err)
	}

	create := false
	for _, writeOption := range writeOptions {
		switch writeOption {
		case vfs.WriteOptionCreate:
			create = true
		case vfs.WriteOptionOnlyIfExists:
			_, err = configPath.ReadFile(ctx)
			if err != nil {
				if os.IsNotExist(err) {
					return fmt.Errorf("cannot update configuration file %s: does not exist", configPath)
				}
				return fmt.Errorf("error checking if configuration file %s exists already: %v", configPath, err)
			}
		default:
			return fmt.Errorf("unknown write option: %q", writeOption)
		}

View on GitHub (pinned to 4c8573c808)

Solutions

1. Inspect the wrapped cause (%v) to find which field/type failed marshaling.
2. Validate/fully populate the object (required fields, correct Kind/APIVersion) before Create/Update.
3. Ensure you use the matching kops API types for the clientset version.
4. If caused by a kops upgrade bug, pin/upgrade kops to a compatible release.

Example fix

// before
cluster := &kops.Cluster{}  // missing ObjectMeta/Spec
clientset.Create(ctx, cluster)
// after
cluster := &kops.Cluster{}
cluster.ObjectMeta.Name = "prod.example.com"
cluster.Spec = kops.ClusterSpec{ /* populated */ }
clientset.Create(ctx, cluster)

if obj == nil || reflect.ValueOf(obj).IsNil() {
    return errors.New("object must be non-nil")
}
if obj.GetObjectKind().GroupVersionKind().Empty() {
    return errors.New("object GroupVersionKind must be set before marshal")
}

func isMarshalable(o interface{}) bool {
    ro, ok := o.(runtime.Object)
    return ok && ro != nil && !reflect.ValueOf(ro).IsNil() && !ro.GetObjectKind().GroupVersionKind().Empty()
}

if err := client.Create(ctx, obj); err != nil && strings.Contains(err.Error(), "error marshaling object") {
    return fmt.Errorf("check object fields/kind: %w", err)
}

When it happens

Trigger: Create/Update on a vfs clientset where the object cannot be encoded by the configured encoder — unregistered type, invalid fields, or nil embedded structs.

Common situations: Programmatically built kops objects missing required fields; passing the wrong object kind to a typed client; kops version mismatch producing objects the current codecs cannot encode.

Related errors

• error encoding object: %v
• error marshaling yaml: %v
• error parsing Cluster %q: %v
• error parsing %s: %v
• ReadOnlyError

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/93239c418b765d82. Report an issue: GitHub.