thanos-io/thanos · error

unknown alertState

Error message

unknown alertState: %v

What it means

Raised in AlertState.UnmarshalJSON when the quoted string decodes fine but does not match any name in AlertState_value (case-insensitively via strings.ToUpper). The JSON carries an alert state label unknown to this build — usually a version mismatch between producer and consumer.

Solutions

1. Use only known AlertState names: inactive, pending, firing
2. Align producer and consumer Thanos/Prometheus versions
3. Check for typos or locale-specific casing in the state string

When it happens

Trigger: Thrown at pkg/rules/rulespb/custom.go:284 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/33076e7813befdcb. Report an issue: GitHub.

Appendix: source

Thrown at pkg/rules/rulespb/custom.go:284

		r.Rules = make([]*Rule, 0)
	}
	type plain RuleGroup
	return json.Marshal((*plain)(r))
}

func (x *AlertState) UnmarshalJSON(entry []byte) error {
	fieldStr, err := strconv.Unquote(string(entry))
	if err != nil {
		return errors.Wrapf(err, "alertState: unquote %v", string(entry))
	}

	if fieldStr == "" {
		return errors.New("empty alertState")
	}

	state, ok := AlertState_value[strings.ToUpper(fieldStr)]
	if !ok {
		return errors.Errorf("unknown alertState: %v", string(entry))
	}
	*x = AlertState(state)
	return nil
}

func (x *AlertState) MarshalJSON() ([]byte, error) {
	return []byte(strconv.Quote(strings.ToLower(x.String()))), nil
}

// Compare compares alert state x and y and returns:
//
//	< 0 if x < y  (alert state x is more critical than alert state y)
//	  0 if x == y
//	> 0 if x > y  (alert state x is less critical than alert state y)
//
// For sorting this makes sure that more "critical" alert states come first.
func (x AlertState) Compare(y AlertState) int {
	return int(y) - int(x)

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