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Add otlptext support for exponential histogram #4642

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Jan 7, 2022
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53 changes: 53 additions & 0 deletions internal/otlptext/databuffer.go
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ package otlptext // import "go.opentelemetry.io/collector/internal/otlptext"
import (
"bytes"
"fmt"
"math"
"strconv"
"strings"

Expand Down Expand Up @@ -78,6 +79,10 @@ func (b *dataBuffer) logMetricDataPoints(m pdata.Metric) {
data := m.Histogram()
b.logEntry(" -> AggregationTemporality: %s", data.AggregationTemporality().String())
b.logDoubleHistogramDataPoints(data.DataPoints())
case pdata.MetricDataTypeExponentialHistogram:
data := m.ExponentialHistogram()
b.logEntry(" -> AggregationTemporality: %s", data.AggregationTemporality().String())
b.logExponentialHistogramDataPoints(data.DataPoints())
case pdata.MetricDataTypeSummary:
data := m.Summary()
b.logDoubleSummaryDataPoints(data.DataPoints())
Expand Down Expand Up @@ -128,6 +133,54 @@ func (b *dataBuffer) logDoubleHistogramDataPoints(ps pdata.HistogramDataPointSli
}
}

func (b *dataBuffer) logExponentialHistogramDataPoints(ps pdata.ExponentialHistogramDataPointSlice) {
for i := 0; i < ps.Len(); i++ {
p := ps.At(i)
b.logEntry("ExponentialHistogramDataPoints #%d", i)
b.logDataPointAttributes(p.Attributes())

b.logEntry("StartTimestamp: %s", p.StartTimestamp())
b.logEntry("Timestamp: %s", p.Timestamp())
b.logEntry("Count: %d", p.Count())
b.logEntry("Sum: %f", p.Sum())

scale := int(p.Scale())
factor := math.Ldexp(math.Ln2, -scale)
// Note: the equation used here, which is
// math.Exp(index * factor)
// reports +Inf as the _lower_ boundary of the bucket nearest
// infinity, which is incorrect and can be addressed in various
// ways. The OTel-Go implementation of this histogram pending
// in https://github.com/open-telemetry/opentelemetry-go/pull/2393
// uses a lookup table for the last finite boundary, which can be
// easily computed using `math/big` (for scales up to 20).

negB := p.Negative().BucketCounts()
posB := p.Positive().BucketCounts()

for i := 0; i < len(negB); i++ {
pos := len(negB) - i - 1
index := p.Negative().Offset() + int32(pos)
count := p.Negative().BucketCounts()[pos]
lower := math.Exp(float64(index) * factor)
upper := math.Exp(float64(index+1) * factor)
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b.logEntry("Bucket (%f, %f], Count: %d", -upper, -lower, count)
}

if p.ZeroCount() != 0 {
b.logEntry("Bucket [0, 0], Count: %d", p.ZeroCount())
}

for pos := 0; pos < len(posB); pos++ {
index := p.Positive().Offset() + int32(pos)
count := p.Positive().BucketCounts()[pos]
lower := math.Exp(float64(index) * factor)
upper := math.Exp(float64(index+1) * factor)
b.logEntry("Bucket [%f, %f), Count: %d", lower, upper, count)
}
}
}

func (b *dataBuffer) logDoubleSummaryDataPoints(ps pdata.SummaryDataPointSlice) {
for i := 0; i < ps.Len(); i++ {
p := ps.At(i)
Expand Down
36 changes: 31 additions & 5 deletions internal/testdata/metric.go
Original file line number Diff line number Diff line change
Expand Up @@ -258,17 +258,43 @@ func initExponentialHistogramMetric(hm pdata.Metric) {
initMetricAttributes13(hdp0.Attributes())
hdp0.SetStartTimestamp(TestMetricStartTimestamp)
hdp0.SetTimestamp(TestMetricTimestamp)
hdp0.SetCount(2)
hdp0.SetSum(15)
hdp0.SetCount(5)
hdp0.SetSum(0.15)
hdp0.SetZeroCount(1)
hdp1 := hdps.AppendEmpty()
hdp0.SetScale(1)

// positive index 1 and 2 are values sqrt(2), 2 at scale 1
hdp0.Positive().SetOffset(1)
hdp0.Positive().SetBucketCounts([]uint64{1, 1})
// negative index -1 and 0 are values -1/sqrt(2), -1 at scale 1
hdp0.Negative().SetOffset(-1)
hdp0.Negative().SetBucketCounts([]uint64{1, 1})

// The above will print:
// Bucket (-1.414214, -1.000000], Count: 1
// Bucket (-1.000000, -0.707107], Count: 1
// Bucket [0, 0], Count: 1
// Bucket [0.707107, 1.000000), Count: 1
// Bucket [1.000000, 1.414214), Count: 1

hdp1 := hdps.AppendEmpty()
initMetricAttributes2(hdp1.Attributes())
hdp1.SetStartTimestamp(TestMetricStartTimestamp)
hdp1.SetTimestamp(TestMetricTimestamp)
hdp1.SetCount(2)
hdp1.SetSum(15)
hdp1.SetCount(3)
hdp1.SetSum(1.25)
hdp1.SetZeroCount(1)
hdp1.SetScale(-1)

// index -1 and 0 are values 0.25, 1 at scale -1
hdp1.Positive().SetOffset(-1)
hdp1.Positive().SetBucketCounts([]uint64{1, 1})

// The above will print:
// Bucket [0, 0], Count: 1
// Bucket [0.250000, 1.000000), Count: 1
// Bucket [1.000000, 4.000000), Count: 1

exemplar := hdp1.Exemplars().AppendEmpty()
exemplar.SetTimestamp(TestMetricExemplarTimestamp)
exemplar.SetDoubleVal(15)
Expand Down