kubernetes/kops · error

K8sClient not set

Error message

K8sClient not set

What it means

drainNode requires a Kubernetes client to evict pods from the node. This guard error means RollingUpdateCluster was constructed without a K8sClient, so draining is impossible. It propagates into drainTerminateAndWait and (with FailOnDrainError) fails the roll.

Source

Thrown at pkg/instancegroups/instancegroups.go:672

		klog.Infof("Stopping instance %q, node %q, in group %q (this may take a while).", id, nodeName, u.CloudInstanceGroup.HumanName)
	} else {
		klog.Infof("Stopping instance %q, in group %q (this may take a while).", id, u.CloudInstanceGroup.HumanName)
	}

	if err := c.Cloud.DeleteInstance(u); err != nil {
		if nodeName != "" {
			return fmt.Errorf("error deleting instance %q, node %q: %v", id, nodeName, err)
		}
		return fmt.Errorf("error deleting instance %q: %v", id, err)
	}

	return nil
}

// drainNode drains a K8s node.
func (c *RollingUpdateCluster) drainNode(ctx context.Context, u *cloudinstances.CloudInstance) error {
	if c.K8sClient == nil {
		return fmt.Errorf("K8sClient not set")
	}

	if u.Node == nil {
		return fmt.Errorf("node not set")
	}

	if u.Node.Name == "" {
		return fmt.Errorf("node name not set")
	}

	helper := &drain.Helper{
		Ctx:                 ctx,
		Client:              c.K8sClient,
		Force:               true,
		GracePeriodSeconds:  -1,
		IgnoreAllDaemonSets: true,
		Out:                 os.Stdout,
		ErrOut:              os.Stderr,

View on GitHub (pinned to 4c8573c808)

Solutions

1. Ensure K8sClient is set when constructing RollingUpdateCluster (clientset from a valid kubeconfig)
2. If no cluster access is intended, use --cloud-only so drain is skipped
3. Verify kubeconfig availability/validity for the target cluster

Example fix

// before
ru := &instancegroups.RollingUpdateCluster{Cloud: cloud, ...} // K8sClient nil
// after
k8sClient, err := kubernetes.NewForConfig(config)
ru := &instancegroups.RollingUpdateCluster{Cloud: cloud, K8sClient: k8sClient, ...}

if c.K8sClient == nil {
    clientset, err := kubernetes.NewForConfig(restConfig)
    if err != nil { return err }
    c.K8sClient = clientset
}

func drainable(c *RollingUpdateCluster) bool { return c != nil && c.K8sClient != nil }

if err := c.drainNode(ctx, u); err != nil {
    if err.Error() == "K8sClient not set" {
        return fmt.Errorf("cannot drain: configure a Kubernetes clientset or use --cloud-only")
    }
    return err
}

When it happens

Trigger: Rolling update invoked without building a kubeconfig-backed clientset — e.g. --cloud-only flows or programmatic use that leaves K8sClient nil while still attempting to drain a registered node.

Common situations: Programmatic/library use of RollingUpdateCluster forgetting to set K8sClient; kops run in an environment where no kubeconfig can be resolved; intentionally cloud-only operations hitting the drain path.

Related errors

• node not set
• building kubernetes client for node labeler: %w
• clientset is not initialized
• getting kubernetes client: %w
• cannot create cluster validator: %v

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/1d270fb52f659b82. Report an issue: GitHub.