You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
prometheus/tsdb/chunkenc/histogram_test.go

696 lines
20 KiB

// Copyright 2021 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package chunkenc
import (
"testing"
"github.com/stretchr/testify/require"
"github.com/prometheus/prometheus/model/histogram"
)
type result struct {
t int64
h *histogram.Histogram
fh *histogram.FloatHistogram
}
func TestHistogramChunkSameBuckets(t *testing.T) {
c := NewHistogramChunk()
var exp []result
// Create fresh appender and add the first histogram.
app, err := c.Appender()
require.NoError(t, err)
require.Equal(t, 0, c.NumSamples())
ts := int64(1234567890)
h := &histogram.Histogram{
Count: 15,
ZeroCount: 2,
Sum: 18.4,
ZeroThreshold: 1e-100,
Schema: 1,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 2},
{Offset: 1, Length: 2},
},
PositiveBuckets: []int64{1, 1, -1, 0}, // counts: 1, 2, 1, 1 (total 5)
NegativeSpans: []histogram.Span{
{Offset: 1, Length: 1},
{Offset: 2, Length: 3},
},
NegativeBuckets: []int64{2, 1, -1, -1}, // counts: 2, 3, 2, 1 (total 8)
}
app.AppendHistogram(ts, h)
exp = append(exp, result{t: ts, h: h, fh: h.ToFloat()})
require.Equal(t, 1, c.NumSamples())
// Add an updated histogram.
ts += 16
h = h.Copy()
h.Count = 32
h.ZeroCount++
h.Sum = 24.4
h.PositiveBuckets = []int64{5, -2, 1, -2} // counts: 5, 3, 4, 2 (total 14)
h.NegativeBuckets = []int64{4, -1, 1, -1} // counts: 4, 3, 4, 4 (total 15)
app.AppendHistogram(ts, h)
hExp := h.Copy()
hExp.CounterResetHint = histogram.NotCounterReset
exp = append(exp, result{t: ts, h: hExp, fh: hExp.ToFloat()})
require.Equal(t, 2, c.NumSamples())
// Add update with new appender.
app, err = c.Appender()
require.NoError(t, err)
ts += 14
h = h.Copy()
h.Count = 54
h.ZeroCount += 2
h.Sum = 24.4
h.PositiveBuckets = []int64{6, 1, -3, 6} // counts: 6, 7, 4, 10 (total 27)
h.NegativeBuckets = []int64{5, 1, -2, 3} // counts: 5, 6, 4, 7 (total 22)
app.AppendHistogram(ts, h)
hExp = h.Copy()
hExp.CounterResetHint = histogram.NotCounterReset
exp = append(exp, result{t: ts, h: hExp, fh: hExp.ToFloat()})
require.Equal(t, 3, c.NumSamples())
// 1. Expand iterator in simple case.
it := c.Iterator(nil)
require.NoError(t, it.Err())
var act []result
for it.Next() == ValHistogram {
ts, h := it.AtHistogram()
fts, fh := it.AtFloatHistogram()
require.Equal(t, ts, fts)
act = append(act, result{t: ts, h: h, fh: fh})
}
require.NoError(t, it.Err())
require.Equal(t, exp, act)
// 2. Expand second iterator while reusing first one.
it2 := c.Iterator(it)
var act2 []result
for it2.Next() == ValHistogram {
ts, h := it2.AtHistogram()
fts, fh := it2.AtFloatHistogram()
require.Equal(t, ts, fts)
act2 = append(act2, result{t: ts, h: h, fh: fh})
}
require.NoError(t, it2.Err())
require.Equal(t, exp, act2)
// 3. Now recycle an iterator that was never used to access anything.
itX := c.Iterator(nil)
for itX.Next() == ValHistogram {
// Just iterate through without accessing anything.
}
it3 := c.iterator(itX)
var act3 []result
for it3.Next() == ValHistogram {
ts, h := it3.AtHistogram()
fts, fh := it3.AtFloatHistogram()
require.Equal(t, ts, fts)
act3 = append(act3, result{t: ts, h: h, fh: fh})
}
require.NoError(t, it3.Err())
require.Equal(t, exp, act3)
// 4. Test iterator Seek.
mid := len(exp) / 2
it4 := c.Iterator(nil)
var act4 []result
require.Equal(t, ValHistogram, it4.Seek(exp[mid].t))
// Below ones should not matter.
require.Equal(t, ValHistogram, it4.Seek(exp[mid].t))
require.Equal(t, ValHistogram, it4.Seek(exp[mid].t))
ts, h = it4.AtHistogram()
fts, fh := it4.AtFloatHistogram()
require.Equal(t, ts, fts)
act4 = append(act4, result{t: ts, h: h, fh: fh})
for it4.Next() == ValHistogram {
ts, h := it4.AtHistogram()
fts, fh := it4.AtFloatHistogram()
require.Equal(t, ts, fts)
act4 = append(act4, result{t: ts, h: h, fh: fh})
}
require.NoError(t, it4.Err())
require.Equal(t, exp[mid:], act4)
require.Equal(t, ValNone, it4.Seek(exp[len(exp)-1].t+1))
}
// Mimics the scenario described for expandSpansForward.
func TestHistogramChunkBucketChanges(t *testing.T) {
c := Chunk(NewHistogramChunk())
// Create fresh appender and add the first histogram.
app, err := c.Appender()
require.NoError(t, err)
require.Equal(t, 0, c.NumSamples())
ts1 := int64(1234567890)
h1 := &histogram.Histogram{
Count: 27,
ZeroCount: 2,
Sum: 18.4,
ZeroThreshold: 1e-125,
Schema: 1,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 2},
{Offset: 2, Length: 1},
{Offset: 3, Length: 2},
{Offset: 3, Length: 1},
{Offset: 1, Length: 1},
},
PositiveBuckets: []int64{6, -3, 0, -1, 2, 1, -4}, // counts: 6, 3, 3, 2, 4, 5, 1 (total 24)
NegativeSpans: []histogram.Span{{Offset: 1, Length: 1}},
NegativeBuckets: []int64{1},
}
app.AppendHistogram(ts1, h1)
require.Equal(t, 1, c.NumSamples())
// Add a new histogram that has expanded buckets.
ts2 := ts1 + 16
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: 0, Length: 3},
{Offset: 1, Length: 1},
{Offset: 1, Length: 4},
{Offset: 3, Length: 3},
}
h2.NegativeSpans = []histogram.Span{{Offset: 0, Length: 2}}
h2.Count = 35
h2.ZeroCount++
h2.Sum = 30
// Existing histogram should get values converted from the above to:
// 6 3 0 3 0 0 2 4 5 0 1 (previous values with some new empty buckets in between)
// so the new histogram should have new counts >= these per-bucket counts, e.g.:
h2.PositiveBuckets = []int64{7, -2, -4, 2, -2, -1, 2, 3, 0, -5, 1} // 7 5 1 3 1 0 2 5 5 0 1 (total 30)
// Existing histogram should get values converted from the above to:
// 0 1 (previous values with some new empty buckets in between)
// so the new histogram should have new counts >= these per-bucket counts, e.g.:
h2.NegativeBuckets = []int64{2, -1} // 2 1 (total 3)
// This is how span changes will be handled.
hApp, _ := app.(*HistogramAppender)
posInterjections, negInterjections, ok, cr := hApp.Appendable(h2)
require.Greater(t, len(posInterjections), 0)
require.Greater(t, len(negInterjections), 0)
require.True(t, ok) // Only new buckets came in.
require.False(t, cr)
c, app = hApp.Recode(posInterjections, negInterjections, h2.PositiveSpans, h2.NegativeSpans)
app.AppendHistogram(ts2, h2)
require.Equal(t, 2, c.NumSamples())
// Because the 2nd histogram has expanded buckets, we should expect all
// histograms (in particular the first) to come back using the new spans
// metadata as well as the expanded buckets.
h1.PositiveSpans = h2.PositiveSpans
h1.PositiveBuckets = []int64{6, -3, -3, 3, -3, 0, 2, 2, 1, -5, 1}
h1.NegativeSpans = h2.NegativeSpans
h1.NegativeBuckets = []int64{0, 1}
hExp := h2.Copy()
hExp.CounterResetHint = histogram.NotCounterReset
exp := []result{
{t: ts1, h: h1, fh: h1.ToFloat()},
{t: ts2, h: hExp, fh: hExp.ToFloat()},
}
it := c.Iterator(nil)
var act []result
for it.Next() == ValHistogram {
ts, h := it.AtHistogram()
fts, fh := it.AtFloatHistogram()
require.Equal(t, ts, fts)
act = append(act, result{t: ts, h: h, fh: fh})
}
require.NoError(t, it.Err())
require.Equal(t, exp, act)
}
func TestHistogramChunkAppendable(t *testing.T) {
c := Chunk(NewHistogramChunk())
// Create fresh appender and add the first histogram.
app, err := c.Appender()
require.NoError(t, err)
require.Equal(t, 0, c.NumSamples())
ts := int64(1234567890)
h1 := &histogram.Histogram{
Count: 5,
ZeroCount: 2,
Sum: 18.4,
ZeroThreshold: 1e-125,
Schema: 1,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 2},
{Offset: 2, Length: 1},
{Offset: 3, Length: 2},
{Offset: 3, Length: 1},
{Offset: 1, Length: 1},
},
PositiveBuckets: []int64{6, -3, 0, -1, 2, 1, -4}, // counts: 6, 3, 3, 2, 4, 5, 1 (total 24)
}
app.AppendHistogram(ts, h1.Copy())
require.Equal(t, 1, c.NumSamples())
hApp, _ := app.(*HistogramAppender)
{ // Schema change.
h2 := h1.Copy()
h2.Schema++
_, _, ok, _ := hApp.Appendable(h2)
require.False(t, ok)
}
{ // Zero threshold change.
h2 := h1.Copy()
h2.ZeroThreshold += 0.1
_, _, ok, _ := hApp.Appendable(h2)
require.False(t, ok)
}
{ // New histogram that has more buckets.
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: 0, Length: 3},
{Offset: 1, Length: 1},
{Offset: 1, Length: 4},
{Offset: 3, Length: 3},
}
h2.Count += 9
h2.ZeroCount++
h2.Sum = 30
// Existing histogram should get values converted from the above to:
// 6 3 0 3 0 0 2 4 5 0 1 (previous values with some new empty buckets in between)
// so the new histogram should have new counts >= these per-bucket counts, e.g.:
h2.PositiveBuckets = []int64{7, -2, -4, 2, -2, -1, 2, 3, 0, -5, 1} // 7 5 1 3 1 0 2 5 5 0 1 (total 30)
posInterjections, negInterjections, ok, cr := hApp.Appendable(h2)
require.Greater(t, len(posInterjections), 0)
require.Equal(t, 0, len(negInterjections))
require.True(t, ok) // Only new buckets came in.
require.False(t, cr)
}
{ // New histogram that has a bucket missing.
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: 0, Length: 2},
{Offset: 5, Length: 2},
{Offset: 3, Length: 1},
{Offset: 1, Length: 1},
}
h2.Sum = 21
h2.PositiveBuckets = []int64{6, -3, -1, 2, 1, -4} // counts: 6, 3, 2, 4, 5, 1 (total 21)
posInterjections, negInterjections, ok, cr := hApp.Appendable(h2)
require.Equal(t, 0, len(posInterjections))
require.Equal(t, 0, len(negInterjections))
require.False(t, ok) // Need to cut a new chunk.
require.True(t, cr)
}
{ // New histogram that has a counter reset while buckets are same.
h2 := h1.Copy()
h2.Sum = 23
h2.PositiveBuckets = []int64{6, -4, 1, -1, 2, 1, -4} // counts: 6, 2, 3, 2, 4, 5, 1 (total 23)
posInterjections, negInterjections, ok, cr := hApp.Appendable(h2)
require.Equal(t, 0, len(posInterjections))
require.Equal(t, 0, len(negInterjections))
require.False(t, ok) // Need to cut a new chunk.
require.True(t, cr)
}
{ // New histogram that has a counter reset while new buckets were added.
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: 0, Length: 3},
{Offset: 1, Length: 1},
{Offset: 1, Length: 4},
{Offset: 3, Length: 3},
}
h2.Sum = 29
// Existing histogram should get values converted from the above to:
// 6 3 0 3 0 0 2 4 5 0 1 (previous values with some new empty buckets in between)
// so the new histogram should have new counts >= these per-bucket counts, e.g.:
h2.PositiveBuckets = []int64{7, -2, -4, 2, -2, -1, 2, 3, 0, -5, 0} // 7 5 1 3 1 0 2 5 5 0 0 (total 29)
posInterjections, negInterjections, ok, cr := hApp.Appendable(h2)
require.Equal(t, 0, len(posInterjections))
require.Equal(t, 0, len(negInterjections))
require.False(t, ok) // Need to cut a new chunk.
require.True(t, cr)
}
{
// New histogram that has a counter reset while new buckets were
// added before the first bucket and reset on first bucket. (to
// catch the edge case where the new bucket should be forwarded
// ahead until first old bucket at start)
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: -3, Length: 2},
{Offset: 1, Length: 2},
{Offset: 2, Length: 1},
{Offset: 3, Length: 2},
{Offset: 3, Length: 1},
{Offset: 1, Length: 1},
}
h2.Sum = 26
// Existing histogram should get values converted from the above to:
// 0, 0, 6, 3, 3, 2, 4, 5, 1
// so the new histogram should have new counts >= these per-bucket counts, e.g.:
h2.PositiveBuckets = []int64{1, 1, 3, -2, 0, -1, 2, 1, -4} // counts: 1, 2, 5, 3, 3, 2, 4, 5, 1 (total 26)
posInterjections, negInterjections, ok, cr := hApp.Appendable(h2)
require.Equal(t, 0, len(posInterjections))
require.Equal(t, 0, len(negInterjections))
require.False(t, ok) // Need to cut a new chunk.
require.True(t, cr)
}
}
func TestAtFloatHistogram(t *testing.T) {
input := []histogram.Histogram{
{
Schema: 0,
Count: 21,
Sum: 1234.5,
ZeroThreshold: 0.001,
ZeroCount: 4,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []int64{1, 1, -1, 0, 0, 0, 0},
NegativeSpans: []histogram.Span{
{Offset: 1, Length: 4},
{Offset: 2, Length: 0},
{Offset: 2, Length: 3},
},
NegativeBuckets: []int64{1, 1, -1, 1, 0, 0, 0},
},
{
Schema: 0,
Count: 36,
Sum: 2345.6,
ZeroThreshold: 0.001,
ZeroCount: 5,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 0},
NegativeSpans: []histogram.Span{
{Offset: 1, Length: 4},
{Offset: 2, Length: 0},
{Offset: 2, Length: 3},
},
NegativeBuckets: []int64{1, 3, -2, 5, -2, 0, -3},
},
{
Schema: 0,
Count: 36,
Sum: 1111.1,
ZeroThreshold: 0.001,
ZeroCount: 5,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []int64{1, 2, -2, 2, -1, 0, 0},
NegativeSpans: []histogram.Span{
{Offset: 1, Length: 4},
{Offset: 2, Length: 0},
{Offset: 2, Length: 3},
},
NegativeBuckets: []int64{1, 3, -2, 5, -1, 0, -3},
},
}
expOutput := []*histogram.FloatHistogram{
{
Schema: 0,
Count: 21,
Sum: 1234.5,
ZeroThreshold: 0.001,
ZeroCount: 4,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []float64{1, 2, 1, 1, 1, 1, 1},
NegativeSpans: []histogram.Span{
{Offset: 1, Length: 4},
{Offset: 2, Length: 0},
{Offset: 2, Length: 3},
},
NegativeBuckets: []float64{1, 2, 1, 2, 2, 2, 2},
},
{
CounterResetHint: histogram.NotCounterReset,
Schema: 0,
Count: 36,
Sum: 2345.6,
ZeroThreshold: 0.001,
ZeroCount: 5,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []float64{1, 3, 1, 2, 1, 1, 1},
NegativeSpans: []histogram.Span{
{Offset: 1, Length: 4},
{Offset: 2, Length: 0},
{Offset: 2, Length: 3},
},
NegativeBuckets: []float64{1, 4, 2, 7, 5, 5, 2},
},
{
CounterResetHint: histogram.NotCounterReset,
Schema: 0,
Count: 36,
Sum: 1111.1,
ZeroThreshold: 0.001,
ZeroCount: 5,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []float64{1, 3, 1, 3, 2, 2, 2},
NegativeSpans: []histogram.Span{
{Offset: 1, Length: 4},
{Offset: 2, Length: 0},
{Offset: 2, Length: 3},
},
NegativeBuckets: []float64{1, 4, 2, 7, 6, 6, 3},
},
}
chk := NewHistogramChunk()
app, err := chk.Appender()
require.NoError(t, err)
for i := range input {
app.AppendHistogram(int64(i), &input[i])
}
it := chk.Iterator(nil)
i := int64(0)
for it.Next() != ValNone {
ts, h := it.AtFloatHistogram()
require.Equal(t, i, ts)
require.Equal(t, expOutput[i], h, "histogram %d unequal", i)
i++
}
}
func TestHistogramChunkAppendableGauge(t *testing.T) {
c := Chunk(NewHistogramChunk())
// Create fresh appender and add the first histogram.
app, err := c.Appender()
require.NoError(t, err)
require.Equal(t, 0, c.NumSamples())
ts := int64(1234567890)
h1 := &histogram.Histogram{
Count: 5,
ZeroCount: 2,
Sum: 18.4,
ZeroThreshold: 1e-125,
Schema: 1,
PositiveSpans: []histogram.Span{
{Offset: 0, Length: 2},
{Offset: 2, Length: 1},
{Offset: 3, Length: 2},
{Offset: 3, Length: 1},
{Offset: 1, Length: 1},
},
PositiveBuckets: []int64{6, -3, 0, -1, 2, 1, -4}, // {6, 3, 3, 2, 4, 5, 1}
}
app.AppendHistogram(ts, h1.Copy())
require.Equal(t, 1, c.NumSamples())
c.(*HistogramChunk).SetCounterResetHeader(GaugeType)
{ // Schema change.
h2 := h1.Copy()
h2.Schema++
hApp, _ := app.(*HistogramAppender)
_, _, _, _, _, _, ok := hApp.AppendableGauge(h2)
require.False(t, ok)
}
{ // Zero threshold change.
h2 := h1.Copy()
h2.ZeroThreshold += 0.1
hApp, _ := app.(*HistogramAppender)
_, _, _, _, _, _, ok := hApp.AppendableGauge(h2)
require.False(t, ok)
}
{ // New histogram that has more buckets.
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: 0, Length: 3},
{Offset: 1, Length: 1},
{Offset: 1, Length: 4},
{Offset: 3, Length: 3},
}
h2.Count += 9
h2.ZeroCount++
h2.Sum = 30
h2.PositiveBuckets = []int64{7, -2, -4, 2, -2, -1, 2, 3, 0, -5, 1} // {7, 5, 1, 3, 1, 0, 2, 5, 5, 0, 1}
hApp, _ := app.(*HistogramAppender)
pI, nI, pBackwardI, nBackwardI, _, _, ok := hApp.AppendableGauge(h2)
require.Greater(t, len(pI), 0)
require.Len(t, nI, 0)
require.Len(t, pBackwardI, 0)
require.Len(t, nBackwardI, 0)
require.True(t, ok)
}
{ // New histogram that has buckets missing.
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: 0, Length: 2},
{Offset: 2, Length: 1},
{Offset: 3, Length: 1},
{Offset: 4, Length: 1},
{Offset: 1, Length: 1},
}
h2.Count -= 4
h2.Sum--
h2.PositiveBuckets = []int64{6, -3, 0, -1, 3, -4} // {6, 3, 3, 2, 5, 1}
hApp, _ := app.(*HistogramAppender)
pI, nI, pBackwardI, nBackwardI, _, _, ok := hApp.AppendableGauge(h2)
require.Len(t, pI, 0)
require.Len(t, nI, 0)
require.Greater(t, len(pBackwardI), 0)
require.Len(t, nBackwardI, 0)
require.True(t, ok)
}
{ // New histogram that has a bucket missing and new buckets.
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: 0, Length: 2},
{Offset: 5, Length: 2},
{Offset: 3, Length: 1},
{Offset: 1, Length: 1},
}
h2.Sum = 21
h2.PositiveBuckets = []int64{6, -3, -1, 2, 1, -4} // {6, 3, 2, 4, 5, 1}
hApp, _ := app.(*HistogramAppender)
pI, nI, pBackwardI, nBackwardI, _, _, ok := hApp.AppendableGauge(h2)
require.Greater(t, len(pI), 0)
require.Greater(t, len(pBackwardI), 0)
require.Len(t, nI, 0)
require.Len(t, nBackwardI, 0)
require.True(t, ok)
}
{ // New histogram that has a counter reset while buckets are same.
h2 := h1.Copy()
h2.Sum = 23
h2.PositiveBuckets = []int64{6, -4, 1, -1, 2, 1, -4} // {6, 2, 3, 2, 4, 5, 1}
hApp, _ := app.(*HistogramAppender)
pI, nI, pBackwardI, nBackwardI, _, _, ok := hApp.AppendableGauge(h2)
require.Len(t, pI, 0)
require.Len(t, nI, 0)
require.Len(t, pBackwardI, 0)
require.Len(t, nBackwardI, 0)
require.True(t, ok)
}
{ // New histogram that has a counter reset while new buckets were added.
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: 0, Length: 3},
{Offset: 1, Length: 1},
{Offset: 1, Length: 4},
{Offset: 3, Length: 3},
}
h2.Sum = 29
h2.PositiveBuckets = []int64{7, -2, -4, 2, -2, -1, 2, 3, 0, -5, 0} // {7, 5, 1, 3, 1, 0, 2, 5, 5, 0, 0}
hApp, _ := app.(*HistogramAppender)
pI, nI, pBackwardI, nBackwardI, _, _, ok := hApp.AppendableGauge(h2)
require.Greater(t, len(pI), 0)
require.Len(t, nI, 0)
require.Len(t, pBackwardI, 0)
require.Len(t, nBackwardI, 0)
require.True(t, ok)
}
{
// New histogram that has a counter reset while new buckets were
// added before the first bucket and reset on first bucket.
h2 := h1.Copy()
h2.PositiveSpans = []histogram.Span{
{Offset: -3, Length: 2},
{Offset: 1, Length: 2},
{Offset: 2, Length: 1},
{Offset: 3, Length: 2},
{Offset: 3, Length: 1},
{Offset: 1, Length: 1},
}
h2.Sum = 26
h2.PositiveBuckets = []int64{1, 1, 3, -2, 0, -1, 2, 1, -4} // {1, 2, 5, 3, 3, 2, 4, 5, 1}
hApp, _ := app.(*HistogramAppender)
pI, nI, pBackwardI, nBackwardI, _, _, ok := hApp.AppendableGauge(h2)
require.Greater(t, len(pI), 0)
require.Len(t, nI, 0)
require.Len(t, pBackwardI, 0)
require.Len(t, nBackwardI, 0)
require.True(t, ok)
}
}