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app/vmselect/promql: properly handle possible negative results caused… (#5608)

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* app/vmselect/promql: properly handle possible negative results caused by float operations precision error in rollup functions like rate() or increase()

* fix test
This commit is contained in:
Hui Wang 2024-01-21 08:53:29 +08:00 committed by Aliaksandr Valialkin
parent bbcec4d10d
commit ff5df0a5aa
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GPG key ID: 52C003EE2BCDB9EB
3 changed files with 18 additions and 1 deletions
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5
app/vmselect/promql/rollup.go
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@ -779,6 +779,11 @@ func removeCounterResets(values []float64) {
}
prevValue = v
values[i] = v + correction
// Check again, there could be precision error in float operations,
// see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5571
if i > 0 && values[i] < values[i-1] {
values[i] = values[i-1]
}
}
}

13
app/vmselect/promql/rollup_test.go
View file

@ -96,7 +96,7 @@ func TestRemoveCounterResets(t *testing.T) {
// removeCounterResets doesn't expect negative values, so it doesn't work properly with them.
values = []float64{-100, -200, -300, -400}
removeCounterResets(values)
valuesExpected = []float64{-100, -300, -600, -1000}
valuesExpected = []float64{-100, -100, -100, -100}
timestampsExpected := []int64{0, 1, 2, 3}
testRowsEqual(t, values, timestampsExpected, valuesExpected, timestampsExpected)
@ -107,6 +107,17 @@ func TestRemoveCounterResets(t *testing.T) {
valuesExpected = []float64{100, 100, 125, 125, 145, 195}
timestampsExpected = []int64{0, 1, 2, 3, 4, 5}
testRowsEqual(t, values, timestampsExpected, valuesExpected, timestampsExpected)
// verify results always increase monotonically with possible float operations precision error
values = []float64{34.094223, 2.7518, 2.140669, 0.044878, 1.887095, 2.546569, 2.490149, 0.045, 0.035684, 0.062454, 0.058296}
removeCounterResets(values)
var prev float64
for i, v := range values {
if v < prev {
t.Fatalf("error: unexpected value keep getting bigger %d; cur %v; pre %v\n", i, v, prev)
}
prev = v
}
}
func TestDeltaValues(t *testing.T) {

1
docs/CHANGELOG.md
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@ -17,6 +17,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
* BUGFIX: [vmselect](https://docs.victoriametrics.com/vmselect.html): properly determine time range search for instant queries with too big look-behind window like `foo[100y]`. Previously, such queries could return empty responses even if `foo` is present in database.
* BUGFIX: properly return errors from [export APIs](https://docs.victoriametrics.com/#how-to-export-time-series). Previously these errors were silently suppressed. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5649).
* BUGFIX: [MetricsQL](https://docs.victoriametrics.com/MetricsQL.html): properly handle possible negative results caused by float operations precision error in rollup functions like rate() or increase(). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5571).
## [v1.87.13](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.87.13)