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lib/promscrape: an attempt to reduce memory usage when vmagent scrapes targets with varying number of metrics

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Do not cache too big byte buffers and too big writeRequestCtx objects,
since it is cheaper to re-create them instead of wasting RAM for their caching.

This reverts 7f6f350ee1
This commit is contained in:
Aliaksandr Valialkin 2021-03-14 22:56:23 +02:00
parent 7f6f350ee1
commit c14dafce43
2 changed files with 26 additions and 32 deletions
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10
lib/leveledbytebufferpool/pool.go
View file

@ -15,7 +15,9 @@ import (
// ...
// pools[n] is for capacities from 2^(n+2)+1 to 2^(n+3)
//
var pools [30]sync.Pool
// Limit the maximum capacity to 2^18, since there are no performance benefits
// in caching byte slices with bigger capacities.
var pools [17]sync.Pool
// Get returns byte buffer with the given capacity.
func Get(capacity int) *bytesutil.ByteBuffer {
@ -37,10 +39,12 @@ func Get(capacity int) *bytesutil.ByteBuffer {
// Put returns bb to the pool.
func Put(bb *bytesutil.ByteBuffer) {
capacity := cap(bb.B)
id, _ := getPoolIDAndCapacity(capacity)
id, poolCapacity := getPoolIDAndCapacity(capacity)
if capacity <= poolCapacity {
bb.Reset()
pools[id].Put(bb)
}
}
func getPoolIDAndCapacity(size int) (int, int) {
size--
@ -49,7 +53,7 @@ func getPoolIDAndCapacity(size int) (int, int) {
}
size >>= 3
id := bits.Len(uint(size))
if id > len(pools) {
if id >= len(pools) {
id = len(pools) - 1
}
return id, (1 << (id + 3))

40
lib/promscrape/scrapework.go
View file

@ -177,9 +177,9 @@ type scrapeWork struct {
// It is used as a hint in order to reduce memory usage for body buffers.
prevBodyLen int
// prevRowsLen contains the number rows scraped during the previous scrape.
// prevLabelsLen contains the number labels scraped during the previous scrape.
// It is used as a hint in order to reduce memory usage when parsing scrape responses.
prevRowsLen int
prevLabelsLen int
}
func (sw *scrapeWork) run(stopCh <-chan struct{}) {
@ -283,7 +283,7 @@ func (sw *scrapeWork) scrapeInternal(scrapeTimestamp, realTimestamp int64) error
scrapeDuration.Update(duration)
scrapeResponseSize.Update(float64(len(body.B)))
up := 1
wc := writeRequestCtxPool.Get(sw.prevRowsLen)
wc := writeRequestCtxPool.Get(sw.prevLabelsLen)
if err != nil {
up = 0
scrapesFailed.Inc()
@ -294,22 +294,10 @@ func (sw *scrapeWork) scrapeInternal(scrapeTimestamp, realTimestamp int64) error
srcRows := wc.rows.Rows
samplesScraped := len(srcRows)
scrapedSamples.Update(float64(samplesScraped))
samplesPostRelabeling := 0
for i := range srcRows {
sw.addRowToTimeseries(wc, &srcRows[i], scrapeTimestamp, true)
if len(wc.labels) > 40000 {
// Limit the maximum size of wc.writeRequest.
// This should reduce memory usage when scraping targets with millions of metrics and/or labels.
// For example, when scraping /federate handler from Prometheus - see https://prometheus.io/docs/prometheus/latest/federation/
samplesPostRelabeling += len(wc.writeRequest.Timeseries)
sw.updateSeriesAdded(wc)
startTime := time.Now()
sw.PushData(&wc.writeRequest)
pushDataDuration.UpdateDuration(startTime)
wc.resetNoRows()
}
}
samplesPostRelabeling += len(wc.writeRequest.Timeseries)
samplesPostRelabeling := len(wc.writeRequest.Timeseries)
if sw.Config.SampleLimit > 0 && samplesPostRelabeling > sw.Config.SampleLimit {
wc.resetNoRows()
up = 0
@ -325,7 +313,7 @@ func (sw *scrapeWork) scrapeInternal(scrapeTimestamp, realTimestamp int64) error
startTime := time.Now()
sw.PushData(&wc.writeRequest)
pushDataDuration.UpdateDuration(startTime)
sw.prevRowsLen = samplesScraped
sw.prevLabelsLen = len(wc.labels)
wc.reset()
writeRequestCtxPool.Put(wc)
// body must be released only after wc is released, since wc refers to body.
@ -339,7 +327,7 @@ func (sw *scrapeWork) scrapeStream(scrapeTimestamp, realTimestamp int64) error {
samplesScraped := 0
samplesPostRelabeling := 0
responseSize := int64(0)
wc := writeRequestCtxPool.Get(sw.prevRowsLen)
wc := writeRequestCtxPool.Get(sw.prevLabelsLen)
sr, err := sw.GetStreamReader()
if err != nil {
@ -389,7 +377,7 @@ func (sw *scrapeWork) scrapeStream(scrapeTimestamp, realTimestamp int64) error {
startTime := time.Now()
sw.PushData(&wc.writeRequest)
pushDataDuration.UpdateDuration(startTime)
sw.prevRowsLen = len(wc.rows.Rows)
sw.prevLabelsLen = len(wc.labels)
wc.reset()
writeRequestCtxPool.Put(wc)
tsmGlobal.Update(sw.Config, sw.ScrapeGroup, up == 1, realTimestamp, int64(duration*1000), err)
@ -401,11 +389,11 @@ func (sw *scrapeWork) scrapeStream(scrapeTimestamp, realTimestamp int64) error {
//
// Its logic has been copied from leveledbytebufferpool.
type leveledWriteRequestCtxPool struct {
pools [30]sync.Pool
pools [13]sync.Pool
}
func (lwp *leveledWriteRequestCtxPool) Get(rowsCapacity int) *writeRequestCtx {
id, capacityNeeded := lwp.getPoolIDAndCapacity(rowsCapacity)
func (lwp *leveledWriteRequestCtxPool) Get(labelsCapacity int) *writeRequestCtx {
id, capacityNeeded := lwp.getPoolIDAndCapacity(labelsCapacity)
for i := 0; i < 2; i++ {
if id < 0 || id >= len(lwp.pools) {
break
@ -421,11 +409,13 @@ func (lwp *leveledWriteRequestCtxPool) Get(rowsCapacity int) *writeRequestCtx {
}
func (lwp *leveledWriteRequestCtxPool) Put(wc *writeRequestCtx) {
capacity := cap(wc.rows.Rows)
id, _ := lwp.getPoolIDAndCapacity(capacity)
capacity := cap(wc.labels)
id, poolCapacity := lwp.getPoolIDAndCapacity(capacity)
if capacity <= poolCapacity {
wc.reset()
lwp.pools[id].Put(wc)
}
}
func (lwp *leveledWriteRequestCtxPool) getPoolIDAndCapacity(size int) (int, int) {
size--
@ -434,7 +424,7 @@ func (lwp *leveledWriteRequestCtxPool) getPoolIDAndCapacity(size int) (int, int)
}
size >>= 3
id := bits.Len(uint(size))
if id > len(lwp.pools) {
if id >= len(lwp.pools) {
id = len(lwp.pools) - 1
}
return id, (1 << (id + 3))