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fix(histogram): handling +Inf bucket count and metric label

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Signed-off-by: Naman-B-Parlecha <namanparlecha@gmail.com>
pull/17166/head
Naman-B-Parlecha 2 months ago
parent 1df1f53ea0
commit f14c515cbe
2 changed files with 34 additions and 44 deletions
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  1. 62
      model/histogram/convert.go
  2. 16
      model/histogram/convert_test.go

62
model/histogram/convert.go
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@ -18,14 +18,18 @@ import (
"fmt"
"math"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/model/labels"
)
// ConvertNHCBToClassic converts Native Histogram Custom Buckets (NHCB) to classic histogram series.
// This conversion is needed in various scenarios where users need to get NHCB back to classic histogram format,
// such as Remote Write v1 for external system compatibility and migration use cases.
//
// When calling this function, caller must ensure that provided nhcb is valid NHCB histogram.
func ConvertNHCBToClassic(nhcb any, lset labels.Labels, lsetBuilder *labels.Builder, emitSeriesFn func(labels labels.Labels, value float64) error) error {
baseName := lset.Get("__name__")
baseName := lset.Get(model.MetricNameLabel)
if baseName == "" {
return errors.New("metric name label '__name__' is missing")
}
@ -50,21 +54,14 @@ func ConvertNHCBToClassic(nhcb any, lset labels.Labels, lsetBuilder *labels.Buil
return errors.New("unsupported histogram schema, not a NHCB")
}
filledBuckets := 0
totalBuckets := 0
for _, span := range h.PositiveSpans {
filledBuckets += int(span.Length)
totalBuckets += int(span.Offset) + int(span.Length)
}
if filledBuckets != len(h.PositiveBuckets) {
return errors.New("mismatched lengths of positive buckets and spans")
}
if totalBuckets > len(h.CustomValues) {
return errors.New("mismatched lengths of custom values and buckets from span calculation")
// Validate the histogram before conversion.
// The caller must ensure that the provided histogram is valid NHCB.
if h.Validate() != nil {
return errors.New(h.Validate().Error())
}
customValues = h.CustomValues
positiveBuckets = make([]float64, len(customValues))
positiveBuckets = make([]float64, len(customValues)+1)
// Histograms are in delta format so we first bring them to absolute format.
acc := int64(0)
@ -87,21 +84,13 @@ func ConvertNHCBToClassic(nhcb any, lset labels.Labels, lsetBuilder *labels.Buil
return errors.New("unsupported histogram schema, not a NHCB")
}
filledBuckets := 0
totalBuckets := 0
for _, s := range h.PositiveSpans {
filledBuckets += int(s.Length)
totalBuckets += int(s.Offset) + int(s.Length)
// Validate the histogram before conversion.
// The caller must ensure that the provided histogram is valid NHCB.
if h.Validate() != nil {
return errors.New(h.Validate().Error())
}
if filledBuckets != len(h.PositiveBuckets) {
return errors.New("mismatched lengths of positive buckets and spans")
}
if totalBuckets > len(h.CustomValues) {
return errors.New("mismatched lengths of custom values and buckets from span calculation")
}
customValues = h.CustomValues
positiveBuckets = make([]float64, len(customValues))
positiveBuckets = make([]float64, len(customValues)+1)
for _, span := range h.PositiveSpans {
// Since Float Histogram is already in absolute format we should
@ -120,39 +109,34 @@ func ConvertNHCBToClassic(nhcb any, lset labels.Labels, lsetBuilder *labels.Buil
return fmt.Errorf("unsupported histogram type: %T", h)
}
// Each customValue corresponds to a positive bucket (aligned with the "le" label).
// The lengths of customValues and positiveBuckets must match to avoid inconsistencies
// while mapping bucket counts to their upper bounds.
if len(customValues) != len(positiveBuckets) {
return errors.New("mismatched lengths of custom values and positive buckets")
}
currCount := float64(0)
for i, val := range customValues {
currCount += positiveBuckets[i]
lsetBuilder.Reset(lset)
lsetBuilder.Set("__name__", baseName+"_bucket")
lsetBuilder.Set("le", labels.FormatOpenMetricsFloat(val))
lsetBuilder.Set(model.MetricNameLabel, baseName+"_bucket")
lsetBuilder.Set(model.BucketLabel, labels.FormatOpenMetricsFloat(val))
if err := emitSeriesFn(lsetBuilder.Labels(), currCount); err != nil {
return err
}
}
currCount += positiveBuckets[len(positiveBuckets)-1]
lsetBuilder.Reset(lset)
lsetBuilder.Set("__name__", baseName+"_bucket")
lsetBuilder.Set("le", labels.FormatOpenMetricsFloat(math.Inf(1)))
lsetBuilder.Set(model.MetricNameLabel, baseName+"_bucket")
lsetBuilder.Set(model.BucketLabel, labels.FormatOpenMetricsFloat(math.Inf(1)))
if err := emitSeriesFn(lsetBuilder.Labels(), currCount); err != nil {
return err
}
lsetBuilder.Reset(lset)
lsetBuilder.Set("__name__", baseName+"_count")
lsetBuilder.Set(model.MetricNameLabel, baseName+"_count")
if err := emitSeriesFn(lsetBuilder.Labels(), count); err != nil {
return err
}
lsetBuilder.Reset(lset)
lsetBuilder.Set("__name__", baseName+"_sum")
lsetBuilder.Set(model.MetricNameLabel, baseName+"_sum")
if err := emitSeriesFn(lsetBuilder.Labels(), sum); err != nil {
return err
}

16
model/histogram/convert_test.go
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@ -136,7 +136,7 @@ func TestConvertNHCBToClassicHistogram(t *testing.T) {
},
},
{
name: "mismatched bucket lengths with more filled bucket count",
name: "extra bucket counts than custom values",
nhcb: &Histogram{
CustomValues: []float64{1, 2},
PositiveBuckets: []int64{10, 20, 30},
@ -145,8 +145,14 @@ func TestConvertNHCBToClassicHistogram(t *testing.T) {
Sum: 100.0,
Schema: CustomBucketsSchema,
},
labels: labels.FromStrings("__name__", "test_metric_bucket"),
expectErr: true,
labels: labels.FromStrings("__name__", "test_metric"),
expected: []sample{
{lset: labels.FromStrings("__name__", "test_metric_bucket", "le", "1.0"), val: 10},
{lset: labels.FromStrings("__name__", "test_metric_bucket", "le", "2.0"), val: 40},
{lset: labels.FromStrings("__name__", "test_metric_bucket", "le", "+Inf"), val: 100},
{lset: labels.FromStrings("__name__", "test_metric_count"), val: 100},
{lset: labels.FromStrings("__name__", "test_metric_sum"), val: 100},
},
},
{
name: "mismatched bucket lengths with less filled bucket count",
@ -234,7 +240,7 @@ func TestConvertNHCBToClassicHistogram(t *testing.T) {
{1, 2},
},
PositiveBuckets: []int64{1, 2, 3, 4, 5}, // 1 -> 3 -> 3 -> 3 -> 3 -> 3 -> 6 ->6 ->10 -> 15
Count: 53, // 1 -> 4 -> 7 -> 10 -> 13 -> 16 -> 22 -> 28 -> 38 -> 53
Count: 35, // 1 -> 4 -> 7 -> 10 -> 13 -> 16 -> 22 -> 28 -> 38 -> 53
Sum: 123,
},
labels: labels.FromStrings("__name__", "test_metric"),
@ -250,7 +256,7 @@ func TestConvertNHCBToClassicHistogram(t *testing.T) {
{lset: labels.FromStrings("__name__", "test_metric_bucket", "le", "9.0"), val: 38},
{lset: labels.FromStrings("__name__", "test_metric_bucket", "le", "10.0"), val: 53},
{lset: labels.FromStrings("__name__", "test_metric_bucket", "le", "+Inf"), val: 53},
{lset: labels.FromStrings("__name__", "test_metric_count"), val: 53},
{lset: labels.FromStrings("__name__", "test_metric_count"), val: 35},
{lset: labels.FromStrings("__name__", "test_metric_sum"), val: 123},
},
},

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