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Support Prometheus native histograms #5777

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#6772
Open
Support Prometheus native histograms#5777
#6772
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enhancementNew feature or requestpkg:exporter:prometheusRelated to the Prometheus exporter package
@dashpole

Description

@dashpole
dashpole
opened on Sep 4, 2024

Problem Statement

We currently drop exponential histograms in the prometheus exporter:

opentelemetry-go/exporters/prometheus/exporter.go

Lines 226 to 239 in 48fedfa

switch v := m.Data.(type) {
case metricdata.Histogram[int64]:
addHistogramMetric(ch, v, m, keys, values, name, c.resourceKeyVals)
case metricdata.Histogram[float64]:
addHistogramMetric(ch, v, m, keys, values, name, c.resourceKeyVals)
case metricdata.Sum[int64]:
addSumMetric(ch, v, m, keys, values, name, c.resourceKeyVals)
case metricdata.Sum[float64]:
addSumMetric(ch, v, m, keys, values, name, c.resourceKeyVals)
case metricdata.Gauge[int64]:
addGaugeMetric(ch, v, m, keys, values, name, c.resourceKeyVals)
case metricdata.Gauge[float64]:
addGaugeMetric(ch, v, m, keys, values, name, c.resourceKeyVals)
}

Proposed Solution

We should convert them to prometheus native histograms per https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/compatibility/prometheus_and_openmetrics.md#exponential-histograms

Additional Context

Related to open-telemetry/opentelemetry-collector-contrib#33703

This is currently difficult to do because we use prometheus.NewConstHistogram here:

opentelemetry-go/exporters/prometheus/exporter.go

Line 256 in 48fedfa

m, err := prometheus.NewConstHistogram(desc, dp.Count, float64(dp.Sum), buckets, values...)

There is no NewConstNativeHistogram in the prometheus client. We would currently need to implement the prometheus.Metric interface directly, which is a bit more work.

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    enhancementNew feature or requestpkg:exporter:prometheusRelated to the Prometheus exporter package

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