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lib/promscrape: optimize per-metric hash calculations

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This increases vmagent performance by up to 10% when scraping big number of metrics
This commit is contained in:
Aliaksandr Valialkin 2020-08-10 19:47:43 +03:00
parent 8adba82c02
commit 1bdfa29ef7
1 changed files with 9 additions and 11 deletions
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20
lib/promscrape/scrapework.go
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@ -135,7 +135,7 @@ type scrapeWork struct {
// the prevSeriesMap and lh are used for fast calculation of `scrape_series_added` metric.
prevSeriesMap map[uint64]struct{}
lh *xxhash.Digest
labelsHashBuf []byte
}
func (sw *scrapeWork) run(stopCh <-chan struct{}) {
@ -248,13 +248,10 @@ func (sw *scrapeWork) scrapeInternal(scrapeTimestamp, realTimestamp int64) error
}
func (sw *scrapeWork) getSeriesAdded() int {
if sw.lh == nil {
sw.lh = xxhash.New()
}
mPrev := sw.prevSeriesMap
seriesAdded := 0
for _, ts := range sw.writeRequest.Timeseries {
h := getLabelsHash(sw.lh, ts.Labels)
h := sw.getLabelsHash(ts.Labels)
if _, ok := mPrev[h]; !ok {
seriesAdded++
}
@ -267,22 +264,23 @@ func (sw *scrapeWork) getSeriesAdded() int {
// Slow path: update the sw.prevSeriesMap, since new time series were added.
m := make(map[uint64]struct{}, len(sw.writeRequest.Timeseries))
for _, ts := range sw.writeRequest.Timeseries {
h := getLabelsHash(sw.lh, ts.Labels)
h := sw.getLabelsHash(ts.Labels)
m[h] = struct{}{}
}
sw.prevSeriesMap = m
return seriesAdded
}
func getLabelsHash(lh *xxhash.Digest, labels []prompbmarshal.Label) uint64 {
func (sw *scrapeWork) getLabelsHash(labels []prompbmarshal.Label) uint64 {
// It is OK if there will be hash collisions for distinct sets of labels,
// since the accuracy for `scrape_series_added` metric may be lower than 100%.
lh.Reset()
b := sw.labelsHashBuf[:0]
for _, label := range labels {
_, _ = lh.WriteString(label.Name)
_, _ = lh.WriteString(label.Value)
b = append(b, label.Name...)
b = append(b, label.Value...)
}
return lh.Sum64()
sw.labelsHashBuf = b
return xxhash.Sum64(b)
}
// addAutoTimeseries adds automatically generated time series with the given name, value and timestamp.