thanos-io/thanos · error

unrecognized label matcher type

Error message

unrecognized label matcher type %d

What it means

The inverse conversion guard: a Thanos LabelMatcher proto carrying a Type outside EQ/NEQ/RE/NRE cannot be mapped to a Prometheus labels.MatchType. Since the proto enum only defines those four values, this fires on out-of-range enum numbers (corrupted or unknown-version wire data), not on normal query input.

Solutions

  1. Check for version skew between the components exchanging storepb matchers
  2. Reject/replace the malformed request data at the boundary
  3. Upgrade both sides to compatible Thanos versions
Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at pkg/store/storepb/custom.go:423 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/f7a6d330f25c975d. Report an issue: GitHub.

Appendix: source

Thrown at pkg/store/storepb/custom.go:423

	}
	return res, nil
}

// MatcherToPromMatcher converts a Thanos label matcher to Prometheus label matcher.
func MatcherToPromMatcher(m LabelMatcher) (*labels.Matcher, error) {
	var t labels.MatchType

	switch m.Type {
	case LabelMatcher_EQ:
		t = labels.MatchEqual
	case LabelMatcher_NEQ:
		t = labels.MatchNotEqual
	case LabelMatcher_RE:
		t = labels.MatchRegexp
	case LabelMatcher_NRE:
		t = labels.MatchNotRegexp
	default:
		return nil, errors.Errorf("unrecognized label matcher type %d", m.Type)
	}
	return labels.NewMatcher(t, m.Name, m.Value)
}

// MatchersToString converts label matchers to string format.
// String should be parsable as a valid PromQL query metric selector.
func MatchersToString(ms ...LabelMatcher) string {
	var res string
	for i, m := range ms {
		res += m.PromString()
		if i < len(ms)-1 {
			res += ", "
		}
	}
	return "{" + res + "}"
}

// PromMatchersToString converts prometheus label matchers to string format.

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