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app/vmselect/promql: reduce overhead on scrape interval estimation

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It should be enough to use the first 20 datapoints instead of 100 datapoints for scrape interval estimation.
This commit is contained in:
Aliaksandr Valialkin 2021-03-15 20:29:27 +02:00
parent 8844b38745
commit 30ab0eec27
1 changed files with 5 additions and 4 deletions
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9
app/vmselect/promql/rollup.go
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@ -538,6 +538,7 @@ func (rc *rollupConfig) doInternal(dstValues []float64, tsm *timeseriesMap, valu
// Do not drop trailing data points for queries, which return 2 or 1 point (aka instant queries). // Do not drop trailing data points for queries, which return 2 or 1 point (aka instant queries).
// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/845 // See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/845
canDropLastSample := rc.CanDropLastSample && len(rc.Timestamps) > 2 canDropLastSample := rc.CanDropLastSample && len(rc.Timestamps) > 2
f := rc.Func
for _, tEnd := range rc.Timestamps { for _, tEnd := range rc.Timestamps {
tStart := tEnd - window tStart := tEnd - window
ni = seekFirstTimestampIdxAfter(timestamps[i:], tStart, ni) ni = seekFirstTimestampIdxAfter(timestamps[i:], tStart, ni)
@ -577,7 +578,7 @@ func (rc *rollupConfig) doInternal(dstValues []float64, tsm *timeseriesMap, valu
rfa.realNextValue = nan rfa.realNextValue = nan
} }
rfa.currTimestamp = tEnd rfa.currTimestamp = tEnd
value := rc.Func(rfa) value := f(rfa)
rfa.idx++ rfa.idx++
dstValues = append(dstValues, value) dstValues = append(dstValues, value)
} }
@ -643,12 +644,12 @@ func getScrapeInterval(timestamps []int64) int64 {
return int64(maxSilenceInterval) return int64(maxSilenceInterval)
} }
// Estimate scrape interval as 0.6 quantile for the first 100 intervals. // Estimate scrape interval as 0.6 quantile for the first 20 intervals.
h := histogram.GetFast() h := histogram.GetFast()
tsPrev := timestamps[0] tsPrev := timestamps[0]
timestamps = timestamps[1:] timestamps = timestamps[1:]
if len(timestamps) > 100 { if len(timestamps) > 20 {
timestamps = timestamps[:100] timestamps = timestamps[:20]
} }
for _, ts := range timestamps { for _, ts := range timestamps {
h.Update(float64(ts - tsPrev)) h.Update(float64(ts - tsPrev))