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app/vmselect/promql: return expected increase() result for the first point on the graph with value not exceeding 100

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Aliaksandr Valialkin 2020-12-15 13:40:30 +02:00
parent 3f88e27d0f
commit 8d1031c29a
2 changed files with 18 additions and 4 deletions
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12
app/vmselect/promql/rollup.go
View file

@ -1308,8 +1308,11 @@ func rollupDelta(rfa *rollupFuncArg) float64 {
// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/894
return values[len(values)-1] - rfa.realPrevValue
}
// Assume that the previous non-existing value was 0
// only if the first value doesn't exceed too much the delta with the next value.
// Assume that the previous non-existing value was 0 only in the following cases:
//
// - If the delta with the next value equals to 0.
// This is the case for slow-changing counter - see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/962
// - If the first value doesn't exceed too much the delta with the next value.
//
// This should prevent from improper increase() results for os-level counters
// such as cpu time or bytes sent over the network interface.
@ -1317,12 +1320,15 @@ func rollupDelta(rfa *rollupFuncArg) float64 {
//
// This also should prevent from improper increase() results when a part of label values are changed
// without counter reset.
d := float64(10)
var d float64
if len(values) > 1 {
d = values[1] - values[0]
} else if !math.IsNaN(rfa.realNextValue) {
d = rfa.realNextValue - values[0]
}
if d == 0 {
d = 10
}
if math.Abs(values[0]) < 10*(math.Abs(d)+1) {
prevValue = 0
} else {

10
app/vmselect/promql/rollup_test.go
View file

@ -1171,8 +1171,16 @@ func TestRollupDelta(t *testing.T) {
f(nan, nan, nan, []float64{5, 6, 8}, 8)
f(2, nan, nan, []float64{5, 6, 8}, 6)
// Too big initial value must be skipped.
// Moderate initial value with zero delta after that.
// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/962
f(nan, nan, nan, []float64{100}, 100)
f(nan, nan, nan, []float64{100, 100}, 100)
// Big initial value with with zero delta after that.
f(nan, nan, nan, []float64{1000}, 0)
f(nan, nan, nan, []float64{1000, 1000}, 0)
// Big initial value with small delta after that.
f(nan, nan, nan, []float64{1000, 1001, 1002}, 2)
// Non-nan realPrevValue