grafana/k6 · error

failed to create gauge for %q: %w

Error message

failed to create gauge for %q: %w

What it means

When a gauge is not yet cached, getOrCreateGauge calls meter.Float64Gauge to create it; an error here (wrapped with the metric name) comes from the OpenTelemetry meter — typically an invalid metric name/unit per OTel semantics. It aborts dispatch of that metric to the exporter.

Source

Thrown at internal/output/opentelemetry/registry.go:126

}

func (r *registry) getOrCreateGauge(name, unit string) (otelMetric.Float64Gauge, error) {
	if gauge, ok := r.gauges.Load(name); ok {
		if v, ok := gauge.(otelMetric.Float64Gauge); ok {
			return v, nil
		}

		return nil, fmt.Errorf("metric %q is not a gauge", name)
	}

	opts := []otelMetric.Float64GaugeOption{}
	if unit != "" {
		opts = append(opts, otelMetric.WithUnit(unit))
	}

	gauge, err := r.meter.Float64Gauge(name, opts...)
	if err != nil {
		return nil, fmt.Errorf("failed to create gauge for %q: %w", name, err)
	}

	r.logger.Debugf("registered gauge metric %q ", name)

	r.gauges.Store(name, gauge)
	return gauge, nil
}

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Check the wrapped error from the meter provider
2. Use a unique metric name for the gauge instrument

When it happens

Trigger: Thrown at internal/output/opentelemetry/registry.go:126 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/89655ea16ab51e36. Report an issue: GitHub.