Add Exponetial Histograms to otlp transforms (#4222)

CHANGELOG.md

@@ -27,6 +27,7 @@ See our [versioning policy](VERSIONING.md) for more information about these stab
 - The `go.opentelemetry.io/otel/semconv/v1.20.0` package.
   The package contains semantic conventions from the `v1.20.0` version of the OpenTelemetry specification. (#4078)
 - The Exponential Histogram data types in `go.opentelemetry.io/otel/sdk/metric/metricdata`. (#4165)
+- OTLP metrics exporter now supports the Exponential Histogram Data Type. (#4222)
 
 ### Changed
 

exporters/otlp/otlpmetric/internal/transform/metricdata.go

@@ -99,6 +99,10 @@ func metric(m metricdata.Metrics) (*mpb.Metric, error) {
 		out.Data, err = Histogram(a)
 	case metricdata.Histogram[float64]:
 		out.Data, err = Histogram(a)
+	case metricdata.ExponentialHistogram[int64]:
+		out.Data, err = ExponentialHistogram(a)
+	case metricdata.ExponentialHistogram[float64]:
+		out.Data, err = ExponentialHistogram(a)
 	default:
 		return out, fmt.Errorf("%w: %T", errUnknownAggregation, a)
 	}
@@ -198,6 +202,61 @@ func HistogramDataPoints[N int64 | float64](dPts []metricdata.HistogramDataPoint
 	return out
 }
 
+// ExponentialHistogram returns an OTLP Metric_ExponentialHistogram generated from h. An error is
+// returned if the temporality of h is unknown.
+func ExponentialHistogram[N int64 | float64](h metricdata.ExponentialHistogram[N]) (*mpb.Metric_ExponentialHistogram, error) {
+	t, err := Temporality(h.Temporality)
+	if err != nil {
+		return nil, err
+	}
+	return &mpb.Metric_ExponentialHistogram{
+		ExponentialHistogram: &mpb.ExponentialHistogram{
+			AggregationTemporality: t,
+			DataPoints:             ExponentialHistogramDataPoints(h.DataPoints),
+		},
+	}, nil
+}
+
+// ExponentialHistogramDataPoints returns a slice of OTLP ExponentialHistogramDataPoint generated
+// from dPts.
+func ExponentialHistogramDataPoints[N int64 | float64](dPts []metricdata.ExponentialHistogramDataPoint[N]) []*mpb.ExponentialHistogramDataPoint {
+	out := make([]*mpb.ExponentialHistogramDataPoint, 0, len(dPts))
+	for _, dPt := range dPts {
+		sum := float64(dPt.Sum)
+		ehdp := &mpb.ExponentialHistogramDataPoint{
+			Attributes:        AttrIter(dPt.Attributes.Iter()),
+			StartTimeUnixNano: uint64(dPt.StartTime.UnixNano()),
+			TimeUnixNano:      uint64(dPt.Time.UnixNano()),
+			Count:             dPt.Count,
+			Sum:               &sum,
+			Scale:             dPt.Scale,
+			ZeroCount:         dPt.ZeroCount,
+
+			Positive: ExponentialHistogramDataPointBuckets(dPt.PositiveBucket),
+			Negative: ExponentialHistogramDataPointBuckets(dPt.NegativeBucket),
+		}
+		if v, ok := dPt.Min.Value(); ok {
+			vF64 := float64(v)
+			ehdp.Min = &vF64
+		}
+		if v, ok := dPt.Max.Value(); ok {
+			vF64 := float64(v)
+			ehdp.Max = &vF64
+		}
+		out = append(out, ehdp)
+	}
+	return out
+}
+
+// ExponentialHistogramDataPointBuckets returns an OTLP ExponentialHistogramDataPoint_Buckets generated
+// from bucket.
+func ExponentialHistogramDataPointBuckets(bucket metricdata.ExponentialBucket) *mpb.ExponentialHistogramDataPoint_Buckets {
+	return &mpb.ExponentialHistogramDataPoint_Buckets{
+		Offset:       bucket.Offset,
+		BucketCounts: bucket.Counts,
+	}
+}
+
 // Temporality returns an OTLP AggregationTemporality generated from t. If t
 // is unknown, an error is returned along with the invalid
 // AggregationTemporality_AGGREGATION_TEMPORALITY_UNSPECIFIED.

exporters/otlp/otlpmetric/internal/transform/metricdata_test.go

@@ -95,6 +95,78 @@ var (
 		Sum:          sumB,
 	}}
 
+	otelEBucketA = metricdata.ExponentialBucket{
+		Offset: 5,
+		Counts: []uint64{0, 5, 0, 5},
+	}
+	otelEBucketB = metricdata.ExponentialBucket{
+		Offset: 3,
+		Counts: []uint64{0, 5, 0, 5},
+	}
+	otelEBucketsC = metricdata.ExponentialBucket{
+		Offset: 5,
+		Counts: []uint64{0, 1},
+	}
+	otelEBucketsD = metricdata.ExponentialBucket{
+		Offset: 3,
+		Counts: []uint64{0, 1},
+	}
+
+	otelEHDPInt64 = []metricdata.ExponentialHistogramDataPoint[int64]{{
+		Attributes:     alice,
+		StartTime:      start,
+		Time:           end,
+		Count:          30,
+		Scale:          2,
+		ZeroCount:      10,
+		PositiveBucket: otelEBucketA,
+		NegativeBucket: otelEBucketB,
+		ZeroThreshold:  .01,
+		Min:            metricdata.NewExtrema(int64(minA)),
+		Max:            metricdata.NewExtrema(int64(maxA)),
+		Sum:            int64(sumA),
+	}, {
+		Attributes:     bob,
+		StartTime:      start,
+		Time:           end,
+		Count:          3,
+		Scale:          4,
+		ZeroCount:      1,
+		PositiveBucket: otelEBucketsC,
+		NegativeBucket: otelEBucketsD,
+		ZeroThreshold:  .02,
+		Min:            metricdata.NewExtrema(int64(minB)),
+		Max:            metricdata.NewExtrema(int64(maxB)),
+		Sum:            int64(sumB),
+	}}
+	otelEHDPFloat64 = []metricdata.ExponentialHistogramDataPoint[float64]{{
+		Attributes:     alice,
+		StartTime:      start,
+		Time:           end,
+		Count:          30,
+		Scale:          2,
+		ZeroCount:      10,
+		PositiveBucket: otelEBucketA,
+		NegativeBucket: otelEBucketB,
+		ZeroThreshold:  .01,
+		Min:            metricdata.NewExtrema(minA),
+		Max:            metricdata.NewExtrema(maxA),
+		Sum:            sumA,
+	}, {
+		Attributes:     bob,
+		StartTime:      start,
+		Time:           end,
+		Count:          3,
+		Scale:          4,
+		ZeroCount:      1,
+		PositiveBucket: otelEBucketsC,
+		NegativeBucket: otelEBucketsD,
+		ZeroThreshold:  .02,
+		Min:            metricdata.NewExtrema(minB),
+		Max:            metricdata.NewExtrema(maxB),
+		Sum:            sumB,
+	}}
+
 	pbHDP = []*mpb.HistogramDataPoint{{
 		Attributes:        []*cpb.KeyValue{pbAlice},
 		StartTimeUnixNano: uint64(start.UnixNano()),
@@ -117,6 +189,49 @@ var (
 		Max:               &maxB,
 	}}
 
+	pbEHDPBA = &mpb.ExponentialHistogramDataPoint_Buckets{
+		Offset:       5,
+		BucketCounts: []uint64{0, 5, 0, 5},
+	}
+	pbEHDPBB = &mpb.ExponentialHistogramDataPoint_Buckets{
+		Offset:       3,
+		BucketCounts: []uint64{0, 5, 0, 5},
+	}
+	pbEHDPBC = &mpb.ExponentialHistogramDataPoint_Buckets{
+		Offset:       5,
+		BucketCounts: []uint64{0, 1},
+	}
+	pbEHDPBD = &mpb.ExponentialHistogramDataPoint_Buckets{
+		Offset:       3,
+		BucketCounts: []uint64{0, 1},
+	}
+
+	pbEHDP = []*mpb.ExponentialHistogramDataPoint{{
+		Attributes:        []*cpb.KeyValue{pbAlice},
+		StartTimeUnixNano: uint64(start.UnixNano()),
+		TimeUnixNano:      uint64(end.UnixNano()),
+		Count:             30,
+		Sum:               &sumA,
+		Scale:             2,
+		ZeroCount:         10,
+		Positive:          pbEHDPBA,
+		Negative:          pbEHDPBB,
+		Min:               &minA,
+		Max:               &maxA,
+	}, {
+		Attributes:        []*cpb.KeyValue{pbBob},
+		StartTimeUnixNano: uint64(start.UnixNano()),
+		TimeUnixNano:      uint64(end.UnixNano()),
+		Count:             3,
+		Sum:               &sumB,
+		Scale:             4,
+		ZeroCount:         1,
+		Positive:          pbEHDPBC,
+		Negative:          pbEHDPBD,
+		Min:               &minB,
+		Max:               &maxB,
+	}}
+
 	otelHistInt64 = metricdata.Histogram[int64]{
 		Temporality: metricdata.DeltaTemporality,
 		DataPoints:  otelHDPInt64,
@@ -131,11 +246,29 @@ var (
 		DataPoints:  otelHDPInt64,
 	}
 
+	otelExpoHistInt64 = metricdata.ExponentialHistogram[int64]{
+		Temporality: metricdata.DeltaTemporality,
+		DataPoints:  otelEHDPInt64,
+	}
+	otelExpoHistFloat64 = metricdata.ExponentialHistogram[float64]{
+		Temporality: metricdata.DeltaTemporality,
+		DataPoints:  otelEHDPFloat64,
+	}
+	otelExpoHistInvalid = metricdata.ExponentialHistogram[int64]{
+		Temporality: invalidTemporality,
+		DataPoints:  otelEHDPInt64,
+	}
+
 	pbHist = &mpb.Histogram{
 		AggregationTemporality: mpb.AggregationTemporality_AGGREGATION_TEMPORALITY_DELTA,
 		DataPoints:             pbHDP,
 	}
 
+	pbExpoHist = &mpb.ExponentialHistogram{
+		AggregationTemporality: mpb.AggregationTemporality_AGGREGATION_TEMPORALITY_DELTA,
+		DataPoints:             pbEHDP,
+	}
+
 	otelDPtsInt64 = []metricdata.DataPoint[int64]{
 		{Attributes: alice, StartTime: start, Time: end, Value: 1},
 		{Attributes: bob, StartTime: start, Time: end, Value: 2},
@@ -263,6 +396,24 @@ var (
 			Unit:        "1",
 			Data:        unknownAgg,
 		},
+		{
+			Name:        "int64-ExponentialHistogram",
+			Description: "Exponential Histogram",
+			Unit:        "1",
+			Data:        otelExpoHistInt64,
+		},
+		{
+			Name:        "float64-ExponentialHistogram",
+			Description: "Exponential Histogram",
+			Unit:        "1",
+			Data:        otelExpoHistFloat64,
+		},
+		{
+			Name:        "invalid-ExponentialHistogram",
+			Description: "Invalid Exponential Histogram",
+			Unit:        "1",
+			Data:        otelExpoHistInvalid,
+		},
 	}
 
 	pbMetrics = []*mpb.Metric{
@@ -302,6 +453,18 @@ var (
 			Unit:        "1",
 			Data:        &mpb.Metric_Histogram{Histogram: pbHist},
 		},
+		{
+			Name:        "int64-ExponentialHistogram",
+			Description: "Exponential Histogram",
+			Unit:        "1",
+			Data:        &mpb.Metric_ExponentialHistogram{ExponentialHistogram: pbExpoHist},
+		},
+		{
+			Name:        "float64-ExponentialHistogram",
+			Description: "Exponential Histogram",
+			Unit:        "1",
+			Data:        &mpb.Metric_ExponentialHistogram{ExponentialHistogram: pbExpoHist},
+		},
 	}
 
 	otelScopeMetrics = []metricdata.ScopeMetrics{{
@@ -368,6 +531,9 @@ func TestTransformations(t *testing.T) {
 	assert.Equal(t, pbHDP, HistogramDataPoints(otelHDPFloat64))
 	assert.Equal(t, pbDPtsInt64, DataPoints[int64](otelDPtsInt64))
 	require.Equal(t, pbDPtsFloat64, DataPoints[float64](otelDPtsFloat64))
+	assert.Equal(t, pbEHDP, ExponentialHistogramDataPoints(otelEHDPInt64))
+	assert.Equal(t, pbEHDP, ExponentialHistogramDataPoints(otelEHDPFloat64))
+	assert.Equal(t, pbEHDPBA, ExponentialHistogramDataPointBuckets(otelEBucketA))
 
 	// Aggregations.
 	h, err := Histogram(otelHistInt64)
@@ -393,6 +559,16 @@ func TestTransformations(t *testing.T) {
 	assert.Equal(t, &mpb.Metric_Gauge{Gauge: pbGaugeInt64}, Gauge[int64](otelGaugeInt64))
 	require.Equal(t, &mpb.Metric_Gauge{Gauge: pbGaugeFloat64}, Gauge[float64](otelGaugeFloat64))
 
+	e, err := ExponentialHistogram(otelExpoHistInt64)
+	assert.NoError(t, err)
+	assert.Equal(t, &mpb.Metric_ExponentialHistogram{ExponentialHistogram: pbExpoHist}, e)
+	e, err = ExponentialHistogram(otelExpoHistFloat64)
+	assert.NoError(t, err)
+	assert.Equal(t, &mpb.Metric_ExponentialHistogram{ExponentialHistogram: pbExpoHist}, e)
+	e, err = ExponentialHistogram(otelExpoHistInvalid)
+	assert.ErrorIs(t, err, errUnknownTemporality)
+	assert.Nil(t, e)
+
 	// Metrics.
 	m, err := Metrics(otelMetrics)
 	assert.ErrorIs(t, err, errUnknownTemporality)