grafana/k6 · error

failed parsing method from expression

Error message

failed parsing method from expression

What it means

parseThresholdAggregationMethod could not recognize the left-hand side: the input is neither one of the aggregation method keywords nor a percentile expression of the form p(number). Generic guard for any unrecognized aggregation method token in the threshold expression.

Source

Thrown at metrics/thresholds_parser.go:213

		if m == input {
			return m, null.Float{}, nil
		}
	}

	// Otherwise, attempt to parse a percentile expression
	if strings.HasPrefix(input, tokenPercentile+"(") && strings.HasSuffix(input, ")") {
		aggregationValue, err := strconv.ParseFloat(trimDelimited("p(", input, ")"), 64)
		if err != nil {
			return "", null.Float{}, fmt.Errorf("malformed percentile value; reason: %w", err)
		}
		if math.IsNaN(aggregationValue) || aggregationValue < 0 || aggregationValue > 100 {
			return "", null.Float{}, fmt.Errorf("malformed percentile value, provide a number between 0 and 100")
		}

		return tokenPercentile, null.FloatFrom(aggregationValue), nil
	}

	return "", null.Float{}, fmt.Errorf("failed parsing method from expression")
}

func trimDelimited(prefix, input, suffix string) string {
	return strings.TrimSuffix(strings.TrimPrefix(input, prefix), suffix)
}

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Use one of the supported methods: avg, min, max, med, count, rate, value, or p(N)
2. Check spelling and casing of the method name
3. Confirm the method applies to the metric type the threshold is set on

When it happens

Trigger: Thrown at metrics/thresholds_parser.go:213 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/03033626175081de. Report an issue: GitHub.