thanos-io/thanos · error

unexpected meta file Thanos section version

Error message

unexpected meta file Thanos section version %d

What it means

Read rejects meta.json files whose thanos section version is not ThanosVersion1 (1). Note the message incorrectly reports m.Version (the TSDB version) instead of the Thanos version. After defaulting version 0 to ThanosVersion1 for backwards compatibility, any other value is rejected.

Solutions

1. Inspect meta.json's "thanos"."version" field; only 0/1 are accepted by this reader.
2. Upgrade Thanos to a version matching the block's thanos meta version.
3. Rewrite the block's meta.json with a compatible writer (e.g. re-upload from source).
4. If hand-edited, restore thanos.version to 1 (or remove it for compatibility default).

Example fix

// before (meta.json)
{"version":1,"thanos":{"version":2,...}}
// after
{"version":1,"thanos":{"version":1,...}}

var raw struct{ Thanos struct{ Version int `json:"version"` } `json:"thanos"` }
b, _ := os.ReadFile(filepath.Join(bdir, "meta.json"))
if json.Unmarshal(b, &raw) == nil {
    if v := raw.Thanos.Version; v != 0 && v != 1 {
        return fmt.Errorf("unsupported thanos meta version %d in %s", v, bdir)
    }
}

func isThanosMetaV1(raw []byte) bool {
    var m struct{ Thanos struct{ Version int `json:"version"` } `json:"thanos"` }
    return json.Unmarshal(raw, &m) == nil && (m.Thanos.Version == 0 || m.Thanos.Version == 1)
}

m, err := metadata.ReadFromDir(ctx, bdir)
if err != nil {
    if strings.Contains(err.Error(), "unexpected meta file Thanos section version") {
        logger.Log("msg", "block written by newer Thanos; upgrade required", "dir", bdir)
        return nil
    }
    return err
}

When it happens

Trigger: Calling Read on a meta.json whose "thanos.version" field is set to a value other than 0 or 1 (e.g. 2) — typically a block written by a newer Thanos with a bumped Thanos meta format.

Common situations: Older Thanos binary reading blocks produced by a newer Thanos that bumped thanos.version; hand-edited thanos section; corrupted meta.json.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• unexpected meta file version
• failed to parse the template
• failed to execute the template
• empty external labels are not allowed for Thanos block.
• read new meta

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/4cb8c175d8b9fdc9. Report an issue: GitHub.

Appendix: source

Thrown at pkg/block/metadata/meta.go:291

	defer runutil.ExhaustCloseWithErrCapture(&err, rc, "close meta JSON")

	var m Meta
	if err = json.NewDecoder(rc).Decode(&m); err != nil {
		return nil, err
	}

	if m.Version != TSDBVersion1 {
		return nil, errors.Errorf("unexpected meta file version %d", m.Version)
	}

	version := m.Thanos.Version
	if version == 0 {
		// For compatibility.
		version = ThanosVersion1
	}

	if version != ThanosVersion1 {
		return nil, errors.Errorf("unexpected meta file Thanos section version %d", m.Version)
	}

	if m.Thanos.Labels == nil {
		// To avoid extra nil checks, allocate map here if empty.
		m.Thanos.Labels = make(map[string]string)
	}
	return &m, nil
}

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