[exporter/awsemfexporter] add exponential histogram support

This PR adds exponential histogram support in awsemfexporter. The exponential histogram metrics are exported in Embedded Metric Format (EMF) log. The Count, Sum, Max and Min are set as Statistical Set. The mid-point values and counts of exponential histogram buckets are translated into Values/Counts array of EMF log entry as well.

.chloggen/awsemf-exponential-histogram.yaml

@@ -0,0 +1,20 @@
+# Use this changelog template to create an entry for release notes.
+# If your change doesn't affect end users, such as a test fix or a tooling change,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: awsemfexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add exponential histogram support.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [22626]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

exporter/awsemfexporter/datapoint.go

@@ -5,6 +5,7 @@ package awsemfexporter // import "github.com/open-telemetry/opentelemetry-collec
 
 import (
 	"fmt"
+	"math"
 	"strconv"
 	"time"
 
@@ -86,6 +87,13 @@ type histogramDataPointSlice struct {
 	pmetric.HistogramDataPointSlice
 }
 
+type exponentialHistogramDataPointSlice struct {
+	// TODO: Calculate delta value for count and sum value with exponential histogram
+	// https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/18245
+	deltaMetricMetadata
+	pmetric.ExponentialHistogramDataPointSlice
+}
+
 // summaryDataPointSlice is a wrapper for pmetric.SummaryDataPointSlice
 type summaryDataPointSlice struct {
 	deltaMetricMetadata
@@ -156,6 +164,79 @@ func (dps histogramDataPointSlice) CalculateDeltaDatapoints(i int, instrumentati
 	}}, true
 }
 
+// CalculateDeltaDatapoints retrieves the ExponentialHistogramDataPoint at the given index.
+func (dps exponentialHistogramDataPointSlice) CalculateDeltaDatapoints(i int, instrumentationScopeName string, detailedMetrics bool) ([]dataPoint, bool) {
+	metric := dps.ExponentialHistogramDataPointSlice.At(i)
+	labels := createLabels(metric.Attributes(), instrumentationScopeName)
+	timestamp := unixNanoToMilliseconds(metric.Timestamp())
+
+	scale := metric.Scale()
+	base := math.Pow(2, math.Pow(2, float64(-scale)))
+	datapoints := []dataPoint{}
+	arrayValues := []float64{}
+	arrayCountes := []float64{}
+
+	// Set mid-point of positive buckets in values/counts array.
+	positiveBuckets := metric.Positive()
+	positiveOffset := positiveBuckets.Offset()
+	positiveBucketCounts := positiveBuckets.BucketCounts()
+	for i := 0; i < positiveBucketCounts.Len(); i++ {
+		index := i + int(positiveOffset)
+		bucketBegin := math.Pow(base, float64(index))
+		bucketEnd := math.Pow(base, float64(index+1))
+		metricVal := (bucketBegin + bucketEnd) / 2
+		count := positiveBucketCounts.At(i)
+		if count > 0 {
+			arrayValues = append(arrayValues, metricVal)
+			arrayCountes = append(arrayCountes, float64(count))
+		}
+	}
+
+	// Set count of zero bucket in values/counts array.
+	if metric.ZeroCount() > 0 {
+		arrayValues = append(arrayValues, 0)
+		arrayCountes = append(arrayCountes, float64(metric.ZeroCount()))
+	}
+
+	// Set mid-point of negative buckets in values/counts array.
+	// According to metrics spec, the value in histogram is expected to be non-negative.
+	// https://opentelemetry.io/docs/specs/otel/metrics/api/#histogram
+	// However, the negative support is defined in metrics data model.
+	// https://opentelemetry.io/docs/specs/otel/metrics/data-model/#exponentialhistogram
+	// The negative is also supported but only verified with unit test.
+	negativeBuckets := metric.Negative()
+	negativeOffset := negativeBuckets.Offset()
+	negativeBucketCounts := negativeBuckets.BucketCounts()
+	for i := 0; i < negativeBucketCounts.Len(); i++ {
+		index := i + int(negativeOffset)
+		bucketBegin := -math.Pow(base, float64(index+1))
+		bucketEnd := -math.Pow(base, float64(index))
+		metricVal := (bucketBegin + bucketEnd) / 2
+		count := negativeBucketCounts.At(i)
+		if count > 0 {
+			arrayValues = append(arrayValues, metricVal)
+			arrayCountes = append(arrayCountes, float64(count))
+		}
+	}
+
+	MetricName := dps.metricName
+	datapoints = append(datapoints, dataPoint{
+		name: MetricName,
+		value: &cWMetricHistogram{
+			Values: arrayValues,
+			Counts: arrayCountes,
+			Count:  metric.Count(),
+			Sum:    metric.Sum(),
+			Max:    metric.Max(),
+			Min:    metric.Min(),
+		},
+		labels:      labels,
+		timestampMs: timestamp,
+	})
+
+	return datapoints, true
+}
+
 // CalculateDeltaDatapoints retrieves the SummaryDataPoint at the given index and perform calculation with sum and count while retain the quantile value.
 func (dps summaryDataPointSlice) CalculateDeltaDatapoints(i int, instrumentationScopeName string, detailedMetrics bool) ([]dataPoint, bool) {
 	metric := dps.SummaryDataPointSlice.At(i)
@@ -263,6 +344,12 @@ func getDataPoints(pmd pmetric.Metric, metadata cWMetricMetadata, logger *zap.Lo
 			metricMetadata,
 			metric.DataPoints(),
 		}
+	case pmetric.MetricTypeExponentialHistogram:
+		metric := pmd.ExponentialHistogram()
+		dps = exponentialHistogramDataPointSlice{
+			metricMetadata,
+			metric.DataPoints(),
+		}
 	case pmetric.MetricTypeSummary:
 		metric := pmd.Summary()
 		// For summaries coming from the prometheus receiver, the sum and count are cumulative, whereas for summaries

exporter/awsemfexporter/datapoint_test.go

@@ -91,6 +91,33 @@ func generateTestHistogramMetric(name string) pmetric.Metrics {
 	return otelMetrics
 }
 
+func generateTestExponentialHistogramMetric(name string) pmetric.Metrics {
+	otelMetrics := pmetric.NewMetrics()
+	rs := otelMetrics.ResourceMetrics().AppendEmpty()
+	metrics := rs.ScopeMetrics().AppendEmpty().Metrics()
+	metric := metrics.AppendEmpty()
+	metric.SetName(name)
+	metric.SetUnit("Seconds")
+	exponentialHistogramMetric := metric.SetEmptyExponentialHistogram()
+
+	exponentialHistogramDatapoint := exponentialHistogramMetric.DataPoints().AppendEmpty()
+	exponentialHistogramDatapoint.SetCount(4)
+	exponentialHistogramDatapoint.SetSum(0)
+	exponentialHistogramDatapoint.SetMin(-4)
+	exponentialHistogramDatapoint.SetMax(4)
+	exponentialHistogramDatapoint.SetZeroCount(0)
+	exponentialHistogramDatapoint.SetScale(1)
+	exponentialHistogramDatapoint.Positive().SetOffset(1)
+	exponentialHistogramDatapoint.Positive().BucketCounts().FromRaw([]uint64{
+		1, 0, 1,
+	})
+	exponentialHistogramDatapoint.Negative().SetOffset(1)
+	exponentialHistogramDatapoint.Negative().BucketCounts().FromRaw([]uint64{
+		1, 0, 1,
+	})
+	return otelMetrics
+}
+
 func generateTestSummaryMetric(name string) pmetric.Metrics {
 	otelMetrics := pmetric.NewMetrics()
 	rs := otelMetrics.ResourceMetrics().AppendEmpty()
@@ -347,6 +374,86 @@ func TestCalculateDeltaDatapoints_HistogramDataPointSlice(t *testing.T) {
 
 }
 
+func TestCalculateDeltaDatapoints_ExponentialHistogramDataPointSlice(t *testing.T) {
+	deltaMetricMetadata := generateDeltaMetricMetadata(false, "foo", false)
+
+	testCases := []struct {
+		name              string
+		histogramDPS      pmetric.ExponentialHistogramDataPointSlice
+		expectedDatapoint dataPoint
+	}{
+		{
+			name: "Histogram with min and max",
+			histogramDPS: func() pmetric.ExponentialHistogramDataPointSlice {
+				histogramDPS := pmetric.NewExponentialHistogramDataPointSlice()
+				histogramDP := histogramDPS.AppendEmpty()
+				histogramDP.SetCount(uint64(17))
+				histogramDP.SetSum(17.13)
+				histogramDP.SetMin(10)
+				histogramDP.SetMax(30)
+				histogramDP.Attributes().PutStr("label1", "value1")
+				return histogramDPS
+			}(),
+			expectedDatapoint: dataPoint{
+				name:   "foo",
+				value:  &cWMetricHistogram{Values: []float64{}, Counts: []float64{}, Sum: 17.13, Count: 17, Min: 10, Max: 30},
+				labels: map[string]string{oTellibDimensionKey: instrLibName, "label1": "value1"},
+			},
+		},
+		{
+			name: "Histogram without min and max",
+			histogramDPS: func() pmetric.ExponentialHistogramDataPointSlice {
+				histogramDPS := pmetric.NewExponentialHistogramDataPointSlice()
+				histogramDP := histogramDPS.AppendEmpty()
+				histogramDP.SetCount(uint64(17))
+				histogramDP.SetSum(17.13)
+				histogramDP.Attributes().PutStr("label1", "value1")
+				return histogramDPS
+
+			}(),
+			expectedDatapoint: dataPoint{
+				name:   "foo",
+				value:  &cWMetricHistogram{Values: []float64{}, Counts: []float64{}, Sum: 17.13, Count: 17, Min: 0, Max: 0},
+				labels: map[string]string{oTellibDimensionKey: instrLibName, "label1": "value1"},
+			},
+		},
+		{
+			name: "Histogram with buckets",
+			histogramDPS: func() pmetric.ExponentialHistogramDataPointSlice {
+				histogramDPS := pmetric.NewExponentialHistogramDataPointSlice()
+				histogramDP := histogramDPS.AppendEmpty()
+				histogramDP.SetCount(uint64(17))
+				histogramDP.SetSum(17.13)
+				histogramDP.Positive().BucketCounts().FromRaw([]uint64{1, 2, 3})
+				histogramDP.Negative().BucketCounts().FromRaw([]uint64{1, 2, 3})
+				histogramDP.Attributes().PutStr("label1", "value1")
+				return histogramDPS
+			}(),
+			expectedDatapoint: dataPoint{
+				name:   "foo",
+				value:  &cWMetricHistogram{Values: []float64{1.5, 3, 6, -1.5, -3, -6}, Counts: []float64{1, 2, 3, 1, 2, 3}, Sum: 17.13, Count: 17, Min: 0, Max: 0},
+				labels: map[string]string{oTellibDimensionKey: instrLibName, "label1": "value1"},
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(_ *testing.T) {
+			// Given the histogram datapoints
+			exponentialHistogramDatapointSlice := exponentialHistogramDataPointSlice{deltaMetricMetadata, tc.histogramDPS}
+
+			// When calculate the delta datapoints for histograms
+			dps, retained := exponentialHistogramDatapointSlice.CalculateDeltaDatapoints(0, instrLibName, false)
+
+			// Then receiving the following datapoint with an expected length
+			assert.True(t, retained)
+			assert.Equal(t, 1, exponentialHistogramDatapointSlice.Len())
+			assert.Equal(t, tc.expectedDatapoint, dps[0])
+		})
+	}
+
+}
+
 func TestCalculateDeltaDatapoints_SummaryDataPointSlice(t *testing.T) {
 	for _, retainInitialValueOfDeltaMetric := range []bool{true, false} {
 		deltaMetricMetadata := generateDeltaMetricMetadata(true, "foo", retainInitialValueOfDeltaMetric)
@@ -486,6 +593,13 @@ func TestGetDataPoints(t *testing.T) {
 			expectedDatapointSlice: histogramDataPointSlice{cumulativeDeltaMetricMetadata, pmetric.HistogramDataPointSlice{}},
 			expectedAttributes:     map[string]interface{}{"label1": "value1"},
 		},
+		{
+			name:                   "ExponentialHistogram",
+			isPrometheusMetrics:    false,
+			metric:                 generateTestExponentialHistogramMetric("foo"),
+			expectedDatapointSlice: exponentialHistogramDataPointSlice{cumulativeDeltaMetricMetadata, pmetric.ExponentialHistogramDataPointSlice{}},
+			expectedAttributes:     map[string]interface{}{"label1": "value1"},
+		},
 		{
 			name:                   "Summary from SDK",
 			isPrometheusMetrics:    false,
@@ -587,6 +701,7 @@ func BenchmarkGetAndCalculateDeltaDataPoints(b *testing.B) {
 		generateTestGaugeMetric("int-gauge", intValueType),
 		generateTestGaugeMetric("int-gauge", doubleValueType),
 		generateTestHistogramMetric("histogram"),
+		generateTestExponentialHistogramMetric("exponential-histogram"),
 		generateTestSumMetric("int-sum", intValueType),
 		generateTestSumMetric("double-sum", doubleValueType),
 		generateTestSummaryMetric("summary"),

exporter/awsemfexporter/metric_translator.go

@@ -56,6 +56,15 @@ type cWMetricStats struct {
 	Sum   float64
 }
 
+type cWMetricHistogram struct {
+	Values []float64
+	Counts []float64
+	Max    float64
+	Min    float64
+	Count  uint64
+	Sum    float64
+}
+
 type groupedMetricMetadata struct {
 	namespace                  string
 	timestampMs                int64