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Fix bug in bucket key calculation #1279

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Merged
merged 2 commits into from
May 28, 2023
Merged

Fix bug in bucket key calculation #1279

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3094812
histogram: expose bug in bucket key calculation
beorn7 May 25, 2023
77e97da
histogram: Fix bug in bucket key calculation
beorn7 May 25, 2023
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4 changes: 2 additions & 2 deletions prometheus/histogram.go
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Original file line number Diff line number Diff line change
Expand Up @@ -639,8 +639,8 @@ func (hc *histogramCounts) observe(v float64, bucket int, doSparse bool) {
if frac == 0.5 {
key--
}
div := 1 << -schema
key = (key + div - 1) / div
offset := (1 << -schema) - 1
key = (key + offset) >> -schema
}
if isInf {
key++
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9 changes: 6 additions & 3 deletions prometheus/histogram_test.go
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Expand Up @@ -500,23 +500,26 @@ func TestNativeHistogram(t *testing.T) {
{
name: "factor 4 results in schema -1",
observations: []float64{
0.0156251, 0.0625, // Bucket -2: (0.015625, 0.0625)
0.1, 0.25, // Bucket -1: (0.0625, 0.25]
0.5, 1, // Bucket 0: (0.25, 1]
1.5, 2, 3, 3.5, // Bucket 1: (1, 4]
5, 6, 7, // Bucket 2: (4, 16]
33.33, // Bucket 3: (16, 64]
},
factor: 4,
want: `sample_count:10 sample_sum:62.83 schema:-1 zero_threshold:2.938735877055719e-39 zero_count:0 positive_span:<offset:0 length:4 > positive_delta:2 positive_delta:2 positive_delta:-1 positive_delta:-2 `,
want: `sample_count:14 sample_sum:63.2581251 schema:-1 zero_threshold:2.938735877055719e-39 zero_count:0 positive_span:<offset:-2 length:6 > positive_delta:2 positive_delta:0 positive_delta:0 positive_delta:2 positive_delta:-1 positive_delta:-2 `,
},
{
name: "factor 17 results in schema -2",
observations: []float64{
0.5, 1, // Bucket 0: (0.0625, 1]
0.0156251, 0.0625, // Bucket -1: (0.015625, 0.0625]
0.1, 0.25, 0.5, 1, // Bucket 0: (0.0625, 1]
1.5, 2, 3, 3.5, 5, 6, 7, // Bucket 1: (1, 16]
33.33, // Bucket 2: (16, 256]
},
factor: 17,
want: `sample_count:10 sample_sum:62.83 schema:-2 zero_threshold:2.938735877055719e-39 zero_count:0 positive_span:<offset:0 length:3 > positive_delta:2 positive_delta:5 positive_delta:-6 `,
want: `sample_count:14 sample_sum:63.2581251 schema:-2 zero_threshold:2.938735877055719e-39 zero_count:0 positive_span:<offset:-1 length:4 > positive_delta:2 positive_delta:2 positive_delta:3 positive_delta:-6 `,
},
{
name: "negative buckets",
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