kubernetes/kops · error

building static config: %w

Error message

building static config: %w

What it means

During etcd-manager pod construction for bare-metal ("metal") clusters, kOps builds a StaticConfig struct (fixed etcd member list) and JSON-serializes it. If json.Marshal fails, the error is wrapped as "building static config: %w". Marshal of this in-memory struct essentially only fails if something injected unsupported types (e.g. non-serializable values via NaN floats), so this is a defensive internal error rather than a user-facing config problem.

Source

Thrown at pkg/model/components/etcdmanager/model.go:545

		case kops.CloudProviderMetal:
			config.VolumeProvider = "external"
			config.BackupStore = "file:///mnt/disks/backups"
			config.VolumeTag = []string{
				fmt.Sprintf("%s--%s--", b.Cluster.Name, etcdCluster.Name),
			}

			staticConfig := &StaticConfig{
				EtcdVersion: etcdCluster.Version,
			}
			staticConfig.Nodes = append(staticConfig.Nodes, StaticConfigNode{
				ID: fmt.Sprintf("%s--%s--%d", b.Cluster.Name, etcdCluster.Name, 0),
				// TODO: Support multiple control-plane nodes (will be interesting!)
				IP: []string{"node0" + "." + etcdCluster.Name + "." + b.Cluster.Name},
			})
			b, err := json.Marshal(staticConfig)
			if err != nil {
				return nil, fmt.Errorf("building static config: %w", err)
			}
			config.StaticConfig = string(b)

		default:
			return nil, fmt.Errorf("CloudProvider %q not supported with etcd-manager", b.Cluster.GetCloudProvider())
		}
	}

	args, err := flagbuilder.BuildFlagsList(config)
	if err != nil {
		return nil, err
	}

	{
		container.Command = []string{"/go-runner"}
		container.Args = []string{
			"--log-file=/var/log/etcd.log",
			"--also-stdout",

View on GitHub (pinned to 4c8573c808)

Solutions

1. Upgrade kOps to the latest patch release, since the wrapped marshal error points to an internal defect
2. Inspect the wrapped inner error (%w) for the exact json.UnsupportedType/Value message to identify which field broke serialization
3. File a kOps issue with the full cluster spec and kOps version if it reproduces on the latest release

// Go caller of buildPod
pod, err := buildPod(ctx, b, etcdCluster)
if err != nil {
    var marshalErr *json.UnsupportedTypeError
    if errors.As(err, &marshalErr) {
        klog.Errorf("static config marshal failed: %v", marshalErr)
    }
    return fmt.Errorf("etcd-manager pod build failed: %w", err)
}

When it happens

Trigger: Running `kops create cluster`/`kops update cluster --target terraform|direct` on a cluster with cloudProvider "metal", causing buildPod (called from buildManifest) to reach the CloudProviderMetal case and call json.Marshal(staticConfig); only fails if marshal returns an error, which for this fixed struct is practically unreachable.

Common situations: Seen in bug reports about bare-metal etcd-manager clusters; almost always indicates a kOps internal bug or a corrupted in-memory cluster spec rather than a user mistake.

Related errors

• error building metal node identifier: %w
• creating metal IPAM controller: %w
• failed to marshal object to JSON: %w
• failed to marsal %q into json: %w
• bare-metal support requires the Metal feature flag to be ena

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/0c66c578a632950c. Report an issue: GitHub.