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Add exemplar support for const histogram #986

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merged 7 commits into from Mar 17, 2022
Merged

Add exemplar support for const histogram #986

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d7f6f6f
Add support for exemplars on constHistogram
arun-shopify Jan 21, 2022
3d744ce
remove GetExemplars function
wperron Feb 15, 2022
ad6f1f6
fixed linting warnings
wperron Feb 15, 2022
47d3c54
Add values to correct bucket
wperron Mar 7, 2022
16ac129
Misc fixes
wperron Mar 11, 2022
daaf45b
avoid panic when there are fewer buckets than exemplars
arun-shopify Mar 9, 2022
3c2e890
Added MustNewMetricWithExemplars that wraps metrics with exemplar (#3)
bwplotka Mar 16, 2022
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60 changes: 59 additions & 1 deletion prometheus/examples_test.go
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Expand Up @@ -22,6 +22,8 @@ import (
"strings"
"time"

"google.golang.org/protobuf/types/known/timestamppb"

//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
"github.com/golang/protobuf/proto"
"github.com/prometheus/common/expfmt"
Expand Down Expand Up @@ -549,11 +551,27 @@ func ExampleNewConstHistogram() {
prometheus.Labels{"owner": "example"},
)

var exemplars []*dto.Exemplar
n := "testName"
v := "testVal"
lp := dto.LabelPair{Name: &n, Value: &v}
var labelPairs []*dto.LabelPair
labelPairs = append(labelPairs, &lp)
vals := []float64{24.0, 42.0, 89.0, 157.0}
t, _ := time.Parse("unix", "Mon Jan _2 15:04:05 MST 2006")
ts := timestamppb.New(t)

for i := 0; i < 4; i++ {
e := dto.Exemplar{Label: labelPairs, Value: &vals[i], Timestamp: ts}
exemplars = append(exemplars, &e)
}

// Create a constant histogram from values we got from a 3rd party telemetry system.
h := prometheus.MustNewConstHistogram(
h := prometheus.MustNewConstHistogramWithExemplar(
desc,
4711, 403.34,
map[float64]uint64{25: 121, 50: 2403, 100: 3221, 200: 4233},
exemplars,
"200", "get",
)

Expand Down Expand Up @@ -583,18 +601,58 @@ func ExampleNewConstHistogram() {
// bucket: <
// cumulative_count: 121
// upper_bound: 25
// exemplar: <
// label: <
// name: "testName"
// value: "testVal"
// >
// value: 24
// timestamp: <
// seconds: -62135596800
// >
// >
// >
// bucket: <
// cumulative_count: 2403
// upper_bound: 50
// exemplar: <
// label: <
// name: "testName"
// value: "testVal"
// >
// value: 42
// timestamp: <
// seconds: -62135596800
// >
// >
// >
// bucket: <
// cumulative_count: 3221
// upper_bound: 100
// exemplar: <
// label: <
// name: "testName"
// value: "testVal"
// >
// value: 89
// timestamp: <
// seconds: -62135596800
// >
// >
// >
// bucket: <
// cumulative_count: 4233
// upper_bound: 200
// exemplar: <
// label: <
// name: "testName"
// value: "testVal"
// >
// value: 157
// timestamp: <
// seconds: -62135596800
// >
// >
// >
// >
}
Expand Down
63 changes: 62 additions & 1 deletion prometheus/histogram.go
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Expand Up @@ -573,6 +573,7 @@ type constHistogram struct {
sum float64
buckets map[float64]uint64
labelPairs []*dto.LabelPair
exemplars []*dto.Exemplar
}

func (h *constHistogram) Desc() *Desc {
Expand All @@ -581,21 +582,39 @@ func (h *constHistogram) Desc() *Desc {

func (h *constHistogram) Write(out *dto.Metric) error {
his := &dto.Histogram{}
// h.buckets, buckets and bounds are all the same length
buckets := make([]*dto.Bucket, 0, len(h.buckets))
bounds := make([]float64, 0, len(h.buckets))

his.SampleCount = proto.Uint64(h.count)
his.SampleSum = proto.Float64(h.sum)

for upperBound, count := range h.buckets {
buckets = append(buckets, &dto.Bucket{
CumulativeCount: proto.Uint64(count),
UpperBound: proto.Float64(upperBound),
})
bounds = append(bounds, upperBound)
}

// make sure that both bounds and buckets have the same ordering
if len(buckets) > 0 {
sort.Sort(buckSort(buckets))
sort.Float64s(bounds)
}

if len(h.exemplars) > 0 {
r := len(buckets)
l := len(h.exemplars)
for i := 0; i < r && i < l; i++ {
bound := sort.SearchFloat64s(bounds, *h.exemplars[i].Value)
// Only append the exemplar if it's within the bounds defined in the
// buckets.
if bound < r {
buckets[bound].Exemplar = h.exemplars[i]
}
}
}

his.Bucket = buckets

out.Histogram = his
Expand All @@ -617,6 +636,7 @@ func (h *constHistogram) Write(out *dto.Metric) error {
//
// NewConstHistogram returns an error if the length of labelValues is not
// consistent with the variable labels in Desc or if Desc is invalid.

func NewConstHistogram(
desc *Desc,
count uint64,
Expand Down Expand Up @@ -655,6 +675,47 @@ func MustNewConstHistogram(
return m
}

func NewConstHistogramWithExemplar(
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Can we use NewConstHistogramWithExemplar in NewConstHistogram for less code repetition?

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Just to clarify, did you mean to use NewConstHistogram inside NewConstHistogramWithExemplar? My goal was to keep the existing API unchanged but whatever you folks prefer is fine by me.

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no, opposite. I think you misunderstood, let me show in PR to your PR 🙃

desc *Desc,
count uint64,
sum float64,
buckets map[float64]uint64,
exemplars []*dto.Exemplar,
labelValues ...string,

) (Metric, error) {
if desc.err != nil {
return nil, desc.err
}
if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
return nil, err
}

h, err := NewConstHistogram(desc, count, sum, buckets, labelValues...)
if err != nil {
return nil, err
}

h.(*constHistogram).exemplars = exemplars

return h, nil
}

// MustNewConstHistogram is a version of NewConstHistogram that panics where
// NewConstHistogram would have returned an error.
func MustNewConstHistogramWithExemplar(
desc *Desc,
count uint64,
sum float64,
buckets map[float64]uint64,
exemplars []*dto.Exemplar,
labelValues ...string,
) Metric {
h := MustNewConstHistogram(desc, count, sum, buckets, labelValues...)
h.(*constHistogram).exemplars = exemplars
return h
}

type buckSort []*dto.Bucket

func (s buckSort) Len() int {
Expand Down
12 changes: 6 additions & 6 deletions prometheus/histogram_test.go
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Expand Up @@ -424,24 +424,24 @@ func TestHistogramExemplar(t *testing.T) {
}
expectedExemplars := []*dto.Exemplar{
nil,
&dto.Exemplar{
{
Label: []*dto.LabelPair{
&dto.LabelPair{Name: proto.String("id"), Value: proto.String("2")},
{Name: proto.String("id"), Value: proto.String("2")},
},
Value: proto.Float64(1.6),
Timestamp: ts,
},
nil,
&dto.Exemplar{
{
Label: []*dto.LabelPair{
&dto.LabelPair{Name: proto.String("id"), Value: proto.String("3")},
{Name: proto.String("id"), Value: proto.String("3")},
},
Value: proto.Float64(4),
Timestamp: ts,
},
&dto.Exemplar{
{
Label: []*dto.LabelPair{
&dto.LabelPair{Name: proto.String("id"), Value: proto.String("4")},
{Name: proto.String("id"), Value: proto.String("4")},
},
Value: proto.Float64(4.5),
Timestamp: ts,
Expand Down