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Optimize PrevEventIDs
when getting thousands of backwards extremeties (#3308)
Changes how many `PrevEventIDs` we send to other servers when backfilling, capped to 100 events. Unsure about how representative this benchmark is.. ``` goos: linux goarch: amd64 pkg: github.com/matrix-org/dendrite/roomserver/api cpu: Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz │ old.txt │ new.txt │ │ sec/op │ sec/op vs base │ PrevEventIDs/Original1-8 264.9n ± 5% 237.4n ± 7% -10.36% (p=0.000 n=10) PrevEventIDs/Original10-8 3.101µ ± 4% 1.590µ ± 2% -48.72% (p=0.000 n=10) PrevEventIDs/Original100-8 44.32µ ± 2% 12.80µ ± 4% -71.11% (p=0.000 n=10) PrevEventIDs/Original500-8 263.835µ ± 4% 7.907µ ± 4% -97.00% (p=0.000 n=10) PrevEventIDs/Original1000-8 578.798µ ± 2% 7.620µ ± 2% -98.68% (p=0.000 n=10) PrevEventIDs/Original2000-8 1272.039µ ± 2% 8.241µ ± 9% -99.35% (p=0.000 n=10) geomean 43.81µ 3.659µ -91.65% │ old.txt │ new.txt │ │ B/op │ B/op vs base │ PrevEventIDs/Original1-8 72.00 ± 0% 48.00 ± 0% -33.33% (p=0.000 n=10) PrevEventIDs/Original10-8 1512.0 ± 0% 500.0 ± 0% -66.93% (p=0.000 n=10) PrevEventIDs/Original100-8 11.977Ki ± 0% 7.023Ki ± 0% -41.36% (p=0.000 n=10) PrevEventIDs/Original500-8 67.227Ki ± 0% 7.023Ki ± 0% -89.55% (p=0.000 n=10) PrevEventIDs/Original1000-8 163.227Ki ± 0% 7.023Ki ± 0% -95.70% (p=0.000 n=10) PrevEventIDs/Original2000-8 347.227Ki ± 0% 7.023Ki ± 0% -97.98% (p=0.000 n=10) geomean 12.96Ki 1.954Ki -84.92% │ old.txt │ new.txt │ │ allocs/op │ allocs/op vs base │ PrevEventIDs/Original1-8 2.000 ± 0% 1.000 ± 0% -50.00% (p=0.000 n=10) PrevEventIDs/Original10-8 6.000 ± 0% 2.000 ± 0% -66.67% (p=0.000 n=10) PrevEventIDs/Original100-8 9.000 ± 0% 3.000 ± 0% -66.67% (p=0.000 n=10) PrevEventIDs/Original500-8 12.000 ± 0% 3.000 ± 0% -75.00% (p=0.000 n=10) PrevEventIDs/Original1000-8 14.000 ± 0% 3.000 ± 0% -78.57% (p=0.000 n=10) PrevEventIDs/Original2000-8 16.000 ± 0% 3.000 ± 0% -81.25% (p=0.000 n=10) geomean 8.137 2.335 -71.31% ```
This commit is contained in:
parent
d357615452
commit
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@ -95,6 +95,12 @@ func Backfill(
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}
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}
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// Enforce a limit of 100 events, as not to hit the DB to hard.
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// Synapse has a hard limit of 100 events as well.
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if req.Limit > 100 {
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req.Limit = 100
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}
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// Query the Roomserver.
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if err = rsAPI.PerformBackfill(httpReq.Context(), &req, &res); err != nil {
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util.GetLogger(httpReq.Context()).WithError(err).Error("query.PerformBackfill failed")
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@ -8,7 +8,6 @@ import (
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"github.com/matrix-org/dendrite/roomserver/types"
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"github.com/matrix-org/gomatrixserverlib"
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"github.com/matrix-org/gomatrixserverlib/spec"
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"github.com/matrix-org/util"
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)
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type PerformCreateRoomRequest struct {
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@ -91,14 +90,44 @@ type PerformBackfillRequest struct {
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VirtualHost spec.ServerName `json:"virtual_host"`
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}
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// PrevEventIDs returns the prev_event IDs of all backwards extremities, de-duplicated in a lexicographically sorted order.
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// limitPrevEventIDs is the maximum of eventIDs we
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// return when calling PrevEventIDs.
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const limitPrevEventIDs = 100
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// PrevEventIDs returns the prev_event IDs of either 100 backwards extremities or
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// len(r.BackwardsExtremities). Limited to 100, due to Synapse/Dendrite stopping after reaching
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// this limit. (which sounds sane)
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func (r *PerformBackfillRequest) PrevEventIDs() []string {
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var prevEventIDs []string
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for _, pes := range r.BackwardsExtremities {
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prevEventIDs = append(prevEventIDs, pes...)
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var uniqueIDs map[string]struct{}
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// Create a unique eventID map of either 100 or len(r.BackwardsExtremities).
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// 100 since Synapse/Dendrite stops after reaching 100 events.
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if len(r.BackwardsExtremities) > limitPrevEventIDs {
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uniqueIDs = make(map[string]struct{}, limitPrevEventIDs)
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} else {
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uniqueIDs = make(map[string]struct{}, len(r.BackwardsExtremities))
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}
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prevEventIDs = util.UniqueStrings(prevEventIDs)
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return prevEventIDs
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outerLoop:
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for _, pes := range r.BackwardsExtremities {
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for _, evID := range pes {
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uniqueIDs[evID] = struct{}{}
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// We found enough unique eventIDs.
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if len(uniqueIDs) >= limitPrevEventIDs {
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break outerLoop
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}
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}
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}
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// map -> []string
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result := make([]string, len(uniqueIDs))
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i := 0
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for evID := range uniqueIDs {
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result[i] = evID
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i++
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}
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return result
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}
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// PerformBackfillResponse is a response to PerformBackfill.
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81
roomserver/api/perform_test.go
Normal file
81
roomserver/api/perform_test.go
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@ -0,0 +1,81 @@
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package api
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import (
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"fmt"
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"math/rand"
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"testing"
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"github.com/stretchr/testify/assert"
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)
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func BenchmarkPrevEventIDs(b *testing.B) {
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for _, x := range []int64{1, 10, 100, 500, 1000, 2000} {
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benchPrevEventIDs(b, int(x))
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}
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}
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func benchPrevEventIDs(b *testing.B, count int) {
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bwExtrems := generateBackwardsExtremities(b, count)
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backfiller := PerformBackfillRequest{
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BackwardsExtremities: bwExtrems,
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}
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b.Run(fmt.Sprintf("Original%d", count), func(b *testing.B) {
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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prevIDs := backfiller.PrevEventIDs()
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_ = prevIDs
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}
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})
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}
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type testLike interface {
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Helper()
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}
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const randomIDCharsCount = 10
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func generateBackwardsExtremities(t testLike, count int) map[string][]string {
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t.Helper()
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result := make(map[string][]string, count)
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for i := 0; i < count; i++ {
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eventID := randomEventId(int64(i))
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result[eventID] = []string{
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randomEventId(int64(i + 1)),
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randomEventId(int64(i + 2)),
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randomEventId(int64(i + 3)),
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}
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}
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return result
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}
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const alphanumerics = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
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// randomEventId generates a pseudo-random string of length n.
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func randomEventId(src int64) string {
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randSrc := rand.NewSource(src)
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b := make([]byte, randomIDCharsCount)
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for i := range b {
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b[i] = alphanumerics[randSrc.Int63()%int64(len(alphanumerics))]
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}
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return string(b)
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}
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func TestPrevEventIDs(t *testing.T) {
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// generate 10 backwards extremities
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bwExtrems := generateBackwardsExtremities(t, 10)
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backfiller := PerformBackfillRequest{
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BackwardsExtremities: bwExtrems,
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}
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prevIDs := backfiller.PrevEventIDs()
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// Given how "generateBackwardsExtremities" works, this
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// generates 12 unique event IDs
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assert.Equal(t, 12, len(prevIDs))
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// generate 200 backwards extremities
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backfiller.BackwardsExtremities = generateBackwardsExtremities(t, 200)
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prevIDs = backfiller.PrevEventIDs()
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// PrevEventIDs returns at max 100 event IDs
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assert.Equal(t, 100, len(prevIDs))
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}
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