func()

in otelcollector/prometheusreceiver/internal/transaction.go [249:307]

• 42 lines of code
• 14 McCabe index (conditional complexity)

func (t *transaction) AppendHistogram(_ storage.SeriesRef, ls labels.Labels, atMs int64, h *histogram.Histogram, fh *histogram.FloatHistogram) (storage.SeriesRef, error) {
	if !t.enableNativeHistograms {
		return 0, nil
	}

	select {
	case <-t.ctx.Done():
		return 0, errTransactionAborted
	default:
	}

	if t.externalLabels.Len() != 0 {
		b := labels.NewBuilder(ls)
		t.externalLabels.Range(func(l labels.Label) {
			b.Set(l.Name, l.Value)
		})
		ls = b.Labels()
	}

	rKey, err := t.initTransaction(ls)
	if err != nil {
		return 0, err
	}

	// Any datapoint with duplicate labels MUST be rejected per:
	// * https://github.com/open-telemetry/wg-prometheus/issues/44
	// * https://github.com/open-telemetry/opentelemetry-collector/issues/3407
	// as Prometheus rejects such too as of version 2.16.0, released on 2020-02-13.
	if dupLabel, hasDup := ls.HasDuplicateLabelNames(); hasDup {
		return 0, fmt.Errorf("invalid sample: non-unique label names: %q", dupLabel)
	}

	metricName := ls.Get(model.MetricNameLabel)
	if metricName == "" {
		return 0, errMetricNameNotFound
	}

	// The `up`, `target_info`, `otel_scope_info` metrics should never generate native histograms,
	// thus we don't check for them here as opposed to the Append function.

	curMF, existing := t.getOrCreateMetricFamily(*rKey, getScopeID(ls), metricName)
	if !existing {
		curMF.mtype = pmetric.MetricTypeExponentialHistogram
	} else if curMF.mtype != pmetric.MetricTypeExponentialHistogram {
		// Already scraped as classic histogram.
		return 0, nil
	}

	if h != nil && h.CounterResetHint == histogram.GaugeType || fh != nil && fh.CounterResetHint == histogram.GaugeType {
		t.logger.Warn("dropping unsupported gauge histogram datapoint", zap.String("metric_name", metricName), zap.Any("labels", ls))
	}

	err = curMF.addExponentialHistogramSeries(t.getSeriesRef(ls, curMF.mtype), metricName, ls, atMs, h, fh)
	if err != nil {
		t.logger.Warn("failed to add histogram datapoint", zap.Error(err), zap.String("metric_name", metricName), zap.Any("labels", ls))
	}

	return 0, nil // never return errors, as that fails the whole scrape
}