kubernetes/kops · error

cannot create cluster validator: %v

Error message

cannot create cluster validator: %v

What it means

With a restConfig in hand, RunRollingUpdateCluster calls validation.NewClusterValidator(cluster, cloud, list, nil, nil, 0, restConfig, k8sClient) to build the validator used to confirm rolling-update progress via the API. If constructing it fails, the error is wrapped as "cannot create cluster validator: %v". This indicates an internal inconsistency — e.g. client construction inside the validator failed despite the restConfig being valid.

Source

Thrown at cmd/kops/rolling-update_cluster.go:465

		fmt.Printf("\nNo rolling-update required.\n")
		return nil
	}

	if !options.Yes {
		fmt.Printf("\nMust specify --yes to rolling-update.\n")
		return nil
	}

	var clusterValidator validation.ClusterValidator
	if !options.CloudOnly {
		restConfig, err := f.RESTConfig(ctx, cluster, options.CreateKubecfgOptions)
		if err != nil {
			return fmt.Errorf("getting rest config: %w", err)
		}

		clusterValidator, err = validation.NewClusterValidator(cluster, cloud, list, nil, nil, 0, restConfig, k8sClient)
		if err != nil {
			return fmt.Errorf("cannot create cluster validator: %v", err)
		}
	}
	d.ClusterValidator = clusterValidator

	return d.RollingUpdate(ctx, groups, list)
}

func completeInstanceGroup(f commandutils.Factory, selectedInstanceGroups *[]string, selectedInstanceGroupRoles *[]string) func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
	return func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
		ctx := cmd.Context()

		commandutils.ConfigureKlogForCompletion()

		cluster, clientSet, completions, directive := GetClusterForCompletion(ctx, f, args)
		if cluster == nil {
			return completions, directive
		}

View on GitHub (pinned to 4c8573c808)

Solutions

1. Check whether k8sClient is nil (kops builds without k8s client imply --cloudonly); pass --cloudonly explicitly
2. Run the same kops version against a matching cluster spec and retry
3. Inspect the wrapped cause (%v) for the underlying failure and fix that (e.g. rebuild kops with CGO/client support)
4. Update kops to the latest patch version if the validator fails deterministically

Example fix

// before
kops rolling-update cluster mycluster.k8s.local
// cannot create cluster validator: unable to create kubernetes client
// after (skip API validation)
kops rolling-update cluster mycluster.k8s.local --cloudonly

// ensure both restConfig and k8sClient are non-nil before validation path
if restConfig == nil || k8sClient == nil {
    return errors.New("cannot build cluster validator without k8s client; use --cloudonly")
}

func canValidate(restConfig *rest.Config, k8sClient kubernetes.Interface) bool {
    return restConfig != nil && k8sClient != nil
}

clusterValidator, err := validation.NewClusterValidator(cluster, cloud, list, nil, nil, 0, restConfig, k8sClient)
if err != nil {
    klog.Warningf("cannot create cluster validator: %v; continuing cloudonly", err)
    // proceed with cloud-only rolling update instead of aborting
}

When it happens

Trigger: validation.NewClusterValidator returns a non-nil error when passed the cluster config, cloud provider, InstanceGroup list, restConfig, and k8sClient — only when --cloudonly is not set.

Common situations: k8sClient is nil (e.g. because kops was built without k8s client support, a known kops case where --cloudonly is implied), mismatched kops/cli and k8s.io/client-go versions, or cloud state contradicting the cluster spec.

Related errors

• failed to parse apiVersion %q
• failed to find kind in object
• invalid InstanceGroup name: %v
• getting kubernetes client: %w
• unexpected error creating validatior: %v

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/a53b0e5699cf0807. Report an issue: GitHub.