[exporter/tanzuobservability] exponential histogram adjustment.

CHANGELOG.md

@@ -26,6 +26,7 @@
 - `datadogexporter`: add error checks for datadog exporter (#9964)
 - `groupbyattrsprocessor`: copied aggregationtemporality when grouping metrics. (#9088)
 - `mongodbreceiver`: Fix issue where receiver startup could hang (#10111)
+- `tanzuobservabilityexporter`: Improve how negative values in exponential histograms are handled. (#10135)
 
 ## v0.51.0
 

exporter/tanzuobservabilityexporter/metrics.go

@@ -710,10 +710,9 @@ func newExponentialHistogramDataPoint(dataPoint pmetric.ExponentialHistogramData
 	positiveBucketCounts := dataPoint.Positive().MBucketCounts()
 
 	// The total number of buckets is the number of negative buckets + the number of positive
-	// buckets + 1 for the zero bucket + 1 bucket for negative infinity up to the negative explicit
-	// bound with largest magnitude + 1 bucket for the largest positive explicit bound up to
+	// buckets + 1 for the zero bucket + 1 bucket for the largest positive explicit bound up to
 	// positive infinity.
-	numBucketCounts := 1 + len(negativeBucketCounts) + 1 + len(positiveBucketCounts) + 1
+	numBucketCounts := len(negativeBucketCounts) + 1 + len(positiveBucketCounts) + 1
 
 	// We pre-allocate the slice setting its length to 0 so that GO doesn't have to keep
 	// re-allocating the slice as it grows.
@@ -748,12 +747,8 @@ func appendNegativeBucketsAndExplicitBounds(
 	bucketCounts *[]uint64,
 	explicitBounds *[]float64,
 ) {
-	// The count in the first bucket which includes negative infinity is always 0.
-	*bucketCounts = append(*bucketCounts, 0)
-
 	// The smallest negative explicit bound.
 	le := -math.Pow(base, float64(negativeOffset)+float64(len(negativeBucketCounts)))
-	*explicitBounds = append(*explicitBounds, le)
 
 	// The first negativeBucketCount has a negative explicit bound with the smallest magnitude;
 	// the last negativeBucketCount has a negative explicit bound with the largest magnitude.

exporter/tanzuobservabilityexporter/metrics_test.go

@@ -1102,10 +1102,10 @@ func TestExponentialHistogramDataPoint(t *testing.T) {
 	dataPoint.Attributes().UpsertString("baz", "7")
 	setDataPointTimestamp(1640198765, dataPoint)
 	h := newExponentialHistogramDataPoint(dataPoint)
-	assert.Equal(t, []uint64{0, 17, 16, 15, 2, 5, 6, 7, 8, 0}, h.MBucketCounts())
+	assert.Equal(t, []uint64{17, 16, 15, 2, 5, 6, 7, 8, 0}, h.MBucketCounts())
 	assert.InDeltaSlice(
 		t,
-		[]float64{-22.6274, -16.0, -11.3137, -8.0, 2.8284, 4.0, 5.6569, 8.0, 11.3137},
+		[]float64{-16.0, -11.3137, -8.0, 2.8284, 4.0, 5.6569, 8.0, 11.3137},
 		h.MExplicitBounds(),
 		0.0001)
 	assert.Equal(t, map[string]string{"foo": "bar", "baz": "7"}, attributesToTags(h.Attributes()))
@@ -1119,8 +1119,8 @@ func TestExponentialHistogramDataPoint_ZeroOnly(t *testing.T) {
 	dataPoint.Positive().SetOffset(1)
 	dataPoint.SetZeroCount(5)
 	h := newExponentialHistogramDataPoint(dataPoint)
-	assert.Equal(t, []uint64{0, 5, 0}, h.MBucketCounts())
-	assert.InDeltaSlice(t, []float64{-4.0, 2.0}, h.MExplicitBounds(), 0.0001)
+	assert.Equal(t, []uint64{5, 0}, h.MBucketCounts())
+	assert.InDeltaSlice(t, []float64{2.0}, h.MExplicitBounds(), 0.0001)
 }
 
 func TestAttributesToTagsForMetrics(t *testing.T) {