grafana/k6 · error

failed to convert Native Histogram to the related Protobuf:

Error message

failed to convert Native Histogram to the related Protobuf: %w

What it means

Error "failed to convert Native Histogram to the related Protobuf: %w" thrown in grafana/k6.

Source

Thrown at internal/output/prometheusrw/remotewrite/trend.go:201

	suffix := baseUnit(series.Metric.Contains)
	labels := MapSeries(series, suffix)
	timestamp := t.UnixMilli()

	return []*prompb.TimeSeries{
		{
			Labels: labels,
			Histograms: []*prompb.Histogram{
				histogramToHistogramProto(timestamp, sink.H),
			},
		},
	}
}

func histogramToHistogramProto(timestamp int64, h prometheus.Histogram) *prompb.Histogram {
	// TODO: research more if a better way is possible.
	metric := &dto.Metric{}
	if err := h.Write(metric); err != nil {
		panic(fmt.Errorf("failed to convert Native Histogram to the related Protobuf: %w", err))
	}
	hmetric := metric.Histogram

	return &prompb.Histogram{
		Count:          &prompb.Histogram_CountInt{CountInt: *hmetric.SampleCount},
		Sum:            *hmetric.SampleSum,
		Schema:         *hmetric.Schema,
		ZeroThreshold:  *hmetric.ZeroThreshold,
		ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: *hmetric.ZeroCount},
		NegativeSpans:  toBucketSpanProto(hmetric.NegativeSpan),
		NegativeDeltas: hmetric.NegativeDelta,
		PositiveSpans:  toBucketSpanProto(hmetric.PositiveSpan),
		PositiveDeltas: hmetric.PositiveDelta,
		Timestamp:      timestamp,
	}
}

func toBucketSpanProto(s []*dto.BucketSpan) []*prompb.BucketSpan {

View on GitHub (pinned to 93accf6570)

When it happens

Trigger: Thrown at internal/output/prometheusrw/remotewrite/trend.go:201 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/9ab180dcf3d0aad1. Report an issue: GitHub.