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Ignore stale histograms for counter reset detection

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The histogram stats decoder keeps track of the last seen histogram sample
in order to properly detect counter resets. We are seeing an issue where
a histogram with UnknownResetHint gets treated as a counter reset when it follows
a stale histogram sample.

I believe that this is incorrect since stale samples should be completely ignored
in PromQL. As a result, they should not be stored in the histogram stats iterator
and the counter reset detection needs to be done against the last non-stale sample.

Signed-off-by: Filip Petkovski <filip.petkovsky@gmail.com>
This commit is contained in:
Filip Petkovski 2024-07-26 09:49:57 +02:00
parent 71c90c71d4
commit be7a4c9b83
No known key found for this signature in database
GPG key ID: 88DE577D81202846
3 changed files with 84 additions and 51 deletions
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2
promql/histogram_stats_iterator.go
View file

@ -48,7 +48,6 @@ func (f *histogramStatsIterator) AtHistogram(h *histogram.Histogram) (int64, *hi
var t int64
t, f.currentH = f.Iterator.AtHistogram(f.currentH)
if value.IsStaleNaN(f.currentH.Sum) {
f.setLastH(f.currentH)
h = &histogram.Histogram{Sum: f.currentH.Sum}
return t, h
}
@ -77,7 +76,6 @@ func (f *histogramStatsIterator) AtFloatHistogram(fh *histogram.FloatHistogram)
var t int64
t, f.currentFH = f.Iterator.AtFloatHistogram(f.currentFH)
if value.IsStaleNaN(f.currentFH.Sum) {
f.setLastFH(f.currentFH)
return t, &histogram.FloatHistogram{Sum: f.currentFH.Sum}
}

79
promql/histogram_stats_iterator_test.go
View file

@ -14,62 +14,99 @@
package promql
import (
"fmt"
"math"
"testing"
"github.com/stretchr/testify/require"
"github.com/prometheus/prometheus/model/histogram"
"github.com/prometheus/prometheus/model/labels"
"github.com/prometheus/prometheus/model/value"
"github.com/prometheus/prometheus/tsdb/chunkenc"
"github.com/prometheus/prometheus/tsdb/tsdbutil"
)
func TestHistogramStatsDecoding(t *testing.T) {
histograms := []*histogram.Histogram{
tsdbutil.GenerateTestHistogram(0),
tsdbutil.GenerateTestHistogram(1),
tsdbutil.GenerateTestHistogram(2),
tsdbutil.GenerateTestHistogram(2),
}
histograms[0].CounterResetHint = histogram.NotCounterReset
histograms[1].CounterResetHint = histogram.UnknownCounterReset
histograms[2].CounterResetHint = histogram.CounterReset
histograms[3].CounterResetHint = histogram.UnknownCounterReset
expectedHints := []histogram.CounterResetHint{
cases := []struct {
name string
histograms []*histogram.Histogram
expectedHints []histogram.CounterResetHint
}{
{
name: "unknown counter reset triggers detection",
histograms: []*histogram.Histogram{
tsdbutil.GenerateTestHistogramWithHint(0, histogram.NotCounterReset),
tsdbutil.GenerateTestHistogramWithHint(1, histogram.UnknownCounterReset),
tsdbutil.GenerateTestHistogramWithHint(2, histogram.CounterReset),
tsdbutil.GenerateTestHistogramWithHint(2, histogram.UnknownCounterReset),
},
expectedHints: []histogram.CounterResetHint{
histogram.NotCounterReset,
histogram.NotCounterReset,
histogram.CounterReset,
histogram.NotCounterReset,
},
},
{
name: "stale sample before unknown reset hint",
histograms: []*histogram.Histogram{
tsdbutil.GenerateTestHistogramWithHint(0, histogram.NotCounterReset),
tsdbutil.GenerateTestHistogramWithHint(1, histogram.UnknownCounterReset),
{Sum: math.Float64frombits(value.StaleNaN)},
tsdbutil.GenerateTestHistogramWithHint(1, histogram.UnknownCounterReset),
},
expectedHints: []histogram.CounterResetHint{
histogram.NotCounterReset,
histogram.NotCounterReset,
histogram.UnknownCounterReset,
histogram.NotCounterReset,
},
},
}
for _, tc := range cases {
t.Run(tc.name, func(t *testing.T) {
t.Run("histogram_stats", func(t *testing.T) {
decodedStats := make([]*histogram.Histogram, 0)
statsIterator := NewHistogramStatsIterator(newHistogramSeries(histograms).Iterator(nil))
statsIterator := NewHistogramStatsIterator(newHistogramSeries(tc.histograms).Iterator(nil))
for statsIterator.Next() != chunkenc.ValNone {
_, h := statsIterator.AtHistogram(nil)
decodedStats = append(decodedStats, h)
}
for i := 0; i < len(histograms); i++ {
require.Equal(t, expectedHints[i], decodedStats[i].CounterResetHint)
require.Equal(t, histograms[i].Count, decodedStats[i].Count)
require.Equal(t, histograms[i].Sum, decodedStats[i].Sum)
for i := 0; i < len(tc.histograms); i++ {
require.Equal(t, tc.expectedHints[i], decodedStats[i].CounterResetHint, fmt.Sprintf("mismatch in counter reset hint for histogram %d", i))
h := tc.histograms[i]
if value.IsStaleNaN(h.Sum) {
require.True(t, value.IsStaleNaN(decodedStats[i].Sum))
require.Equal(t, uint64(0), decodedStats[i].Count)
} else {
require.Equal(t, tc.histograms[i].Count, decodedStats[i].Count)
require.Equal(t, tc.histograms[i].Sum, decodedStats[i].Sum)
}
}
})
t.Run("float_histogram_stats", func(t *testing.T) {
decodedStats := make([]*histogram.FloatHistogram, 0)
statsIterator := NewHistogramStatsIterator(newHistogramSeries(histograms).Iterator(nil))
statsIterator := NewHistogramStatsIterator(newHistogramSeries(tc.histograms).Iterator(nil))
for statsIterator.Next() != chunkenc.ValNone {
_, h := statsIterator.AtFloatHistogram(nil)
decodedStats = append(decodedStats, h)
}
for i := 0; i < len(histograms); i++ {
fh := histograms[i].ToFloat(nil)
require.Equal(t, expectedHints[i], decodedStats[i].CounterResetHint)
for i := 0; i < len(tc.histograms); i++ {
require.Equal(t, tc.expectedHints[i], decodedStats[i].CounterResetHint)
fh := tc.histograms[i].ToFloat(nil)
if value.IsStaleNaN(fh.Sum) {
require.True(t, value.IsStaleNaN(decodedStats[i].Sum))
require.Equal(t, float64(0), decodedStats[i].Count)
} else {
require.Equal(t, fh.Count, decodedStats[i].Count)
require.Equal(t, fh.Sum, decodedStats[i].Sum)
}
}
})
})
}
}
type histogramSeries struct {

10
tsdb/tsdbutil/histogram.go
View file

@ -30,12 +30,10 @@ func GenerateTestHistograms(n int) (r []*histogram.Histogram) {
return r
}
func GenerateTestHistogramsWithUnknownResetHint(n int) []*histogram.Histogram {
hs := GenerateTestHistograms(n)
for i := range hs {
hs[i].CounterResetHint = histogram.UnknownCounterReset
}
return hs
func GenerateTestHistogramWithHint(n int, hint histogram.CounterResetHint) *histogram.Histogram {
h := GenerateTestHistogram(n)
h.CounterResetHint = hint
return h
}
// GenerateTestHistogram but it is up to the user to set any known counter reset hint.