grafana/k6 · error

failed to create histogram for %q: %w

Error message

failed to create histogram for %q: %w

What it means

The OTel Meter rejected creation of a Float64Histogram instrument for this metric name. getOrCreateHistogram wraps the SDK error, typically a name conflict with an existing instrument of another kind.

Source

Thrown at internal/output/opentelemetry/registry.go:71

}

func (r *registry) getOrCreateHistogram(name, unit string) (otelMetric.Float64Histogram, error) {
	if histogram, ok := r.histograms.Load(name); ok {
		if v, ok := histogram.(otelMetric.Float64Histogram); ok {
			return v, nil
		}

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

	opts := []otelMetric.Float64HistogramOption{}
	if unit != "" {
		opts = append(opts, otelMetric.WithUnit(unit))
	}

	h, err := r.meter.Float64Histogram(name, opts...)
	if err != nil {
		return nil, fmt.Errorf("failed to create histogram for %q: %w", name, err)
	}

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

	r.histograms.Store(name, h)
	return h, nil
}

func (r *registry) getOrCreateCounterForRate(name string) (otelMetric.Int64Counter, error) {
	// k6's rate metric tracks how frequently a non-zero value occurs.
	// To be accurate is a percentage, which is a ratio.
	// To correctly calculate this metric in a metrics backend,
	// we need to split the rate metric via a dedicated attribute.

	totalName := name + ".total"

	var err error
	var totalCounter otelMetric.Int64Counter

View on GitHub (pinned to 01ffac6f24)

Solutions

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

When it happens

Trigger: Thrown at internal/output/opentelemetry/registry.go:71 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/c33c85c976b56d14. Report an issue: GitHub.