kubernetes/kops · error

creating discovery client: %w

Error message

creating discovery client: %w

What it means

After listing namespaces, DumpResources builds a discovery client via discovery.NewDiscoveryClientForConfig(d.k8sConfig) to query the server's preferred API resources. This error wraps a failure to construct the REST client itself, which is rare because construction only fails on invalid rest.Config (e.g. unparsable host URL, conflicting TLS settings) rather than on network problems.

Source

Thrown at pkg/dump/resourcedumper.go:110

		artifactsDir:  artifactsDir,
	}, nil
}

func (d *resourceDumper) DumpResources(ctx context.Context) error {
	klog.Info("Dumping k8s resources")
	clientSet, err := kubernetes.NewForConfig(d.k8sConfig)
	if err != nil {
		return fmt.Errorf("creating clientset: %w", err)
	}

	namespaces, err := clientSet.CoreV1().Namespaces().List(ctx, metav1.ListOptions{})
	if err != nil {
		return fmt.Errorf("listing namespaces: %w", err)
	}

	discoveryClient, err := discovery.NewDiscoveryClientForConfig(d.k8sConfig)
	if err != nil {
		return fmt.Errorf("creating discovery client: %w", err)
	}

	resourceLists, err := discoveryClient.ServerPreferredResources()
	var discoveryErr *discovery.ErrGroupDiscoveryFailed
	if errors.As(err, &discoveryErr) {
		klog.Warningf("using incomplete list of API groups: %v", discoveryErr)
	} else if err != nil {
		return fmt.Errorf("listing server preferred resources: %w", err)
	}

	gvrNamespaces, err := getGVRNamespaces(resourceLists, namespaces.Items)
	if err != nil {
		return fmt.Errorf("getting GVR namespaces: %w", err)
	}

	jobs := make(chan gvrNamespace, len(gvrNamespaces))
	results := make(chan resourceDumpResult, len(gvrNamespaces))

View on GitHub (pinned to 4c8573c808)

Solutions

1. Inspect d.k8sConfig (Host, TLS fields) and fix invalid values before calling NewResourceDumper.
2. Build the config from a known-good source via clientcmd or rest.InClusterConfig instead of hand-constructing it.
3. Confirm NewResourceDumper's dynamic.NewForConfig succeeded (same config), isolating the field that discovery-specific construction rejects.

if cfg.Host == "" {
	return fmt.Errorf("rest.Config.Host is empty")
}
u, err := url.Parse(cfg.Host)
if err != nil || (u.Scheme != "https" && u.Scheme != "http") {
	return fmt.Errorf("invalid rest.Config.Host %q", cfg.Host)
}
if _, err := dynamic.NewForConfig(cfg); err != nil {
	return fmt.Errorf("config rejected by client construction: %w", err)
}

if err := dumper.DumpResources(ctx); err != nil {
	var ce *url.Error
	if strings.Contains(err.Error(), "creating discovery client") {
		// config construction problem: log rest.Config (redact secrets) and fix Host/TLS
	}
	_ = ce
	return err
}

When it happens

Trigger: d.k8sConfig has a malformed Host, invalid TLS/cert configuration, or other fields that rest.RESTClientFor rejects during client construction.

Common situations: Programmatically mutated rest.Config (bad URL scheme, whitespace in host), a config assembled without setting Host at all, or a TLS key/cert pair that cannot be loaded into transport config.

Related errors

• error building corev1 client: %v
• cannot build kube client: %w
• cannot load kubecfg settings for %q: %w
• cannot build kube client for %q: %w
• building kubernetes client: %w

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/2db569f0bc84602d. Report an issue: GitHub.