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core/region: optimize the efficiency of random regions selecting #8205

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merged 6 commits into from
May 22, 2024
Merged

core/region: optimize the efficiency of random regions selecting #8205

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f83fc7b
Optimize the efficiency of random regions selecting
JmPotato May 21, 2024
aea156a
Remove the unused code
JmPotato May 21, 2024
7df701c
Refine the code
JmPotato May 22, 2024
228db1d
Fix the check
JmPotato May 22, 2024
12142ed
Address the comments
JmPotato May 22, 2024
a932eb2
Merge branch 'master' into refine_randome_regions
ti-chi-bot[bot] May 22, 2024
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39 changes: 8 additions & 31 deletions pkg/core/region.go
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Original file line number Diff line number Diff line change
Expand Up @@ -727,6 +727,11 @@ func (r *RegionInfo) isRegionRecreated() bool {
return r.GetRegionEpoch().GetVersion() == 1 && r.GetRegionEpoch().GetConfVer() == 1 && (len(r.GetStartKey()) != 0 || len(r.GetEndKey()) != 0)
}

func (r *RegionInfo) Contains(key []byte) bool {
start, end := r.GetStartKey(), r.GetEndKey()
return bytes.Compare(key, start) >= 0 && (len(end) == 0 || bytes.Compare(key, end) < 0)
}

// RegionGuideFunc is a function that determines which follow-up operations need to be performed based on the origin
// and new region information.
type RegionGuideFunc func(ctx *MetaProcessContext, region, origin *RegionInfo) (saveKV, saveCache, needSync, retained bool)
Expand Down Expand Up @@ -1673,25 +1678,18 @@ func (r *RegionsInfo) GetStoreWitnessCount(storeID uint64) int {
return r.witnesses[storeID].length()
}

// RandPendingRegion randomly gets a store's region with a pending peer.
func (r *RegionsInfo) RandPendingRegion(storeID uint64, ranges []KeyRange) *RegionInfo {
r.st.RLock()
defer r.st.RUnlock()
return r.pendingPeers[storeID].RandomRegion(ranges)
}

// RandPendingRegions randomly gets a store's n regions with a pending peer.
func (r *RegionsInfo) RandPendingRegions(storeID uint64, ranges []KeyRange) []*RegionInfo {
r.st.RLock()
defer r.st.RUnlock()
return r.pendingPeers[storeID].RandomRegions(randomRegionMaxRetry, ranges)
}

// RandLeaderRegion randomly gets a store's leader region.
func (r *RegionsInfo) RandLeaderRegion(storeID uint64, ranges []KeyRange) *RegionInfo {
// This function is used for test only.
func (r *RegionsInfo) randLeaderRegion(storeID uint64, ranges []KeyRange) {
r.st.RLock()
defer r.st.RUnlock()
return r.leaders[storeID].RandomRegion(ranges)
_ = r.leaders[storeID].randomRegion(ranges)
}

// RandLeaderRegions randomly gets a store's n leader regions.
Expand All @@ -1701,41 +1699,20 @@ func (r *RegionsInfo) RandLeaderRegions(storeID uint64, ranges []KeyRange) []*Re
return r.leaders[storeID].RandomRegions(randomRegionMaxRetry, ranges)
}

// RandFollowerRegion randomly gets a store's follower region.
func (r *RegionsInfo) RandFollowerRegion(storeID uint64, ranges []KeyRange) *RegionInfo {
r.st.RLock()
defer r.st.RUnlock()
return r.followers[storeID].RandomRegion(ranges)
}

// RandFollowerRegions randomly gets a store's n follower regions.
func (r *RegionsInfo) RandFollowerRegions(storeID uint64, ranges []KeyRange) []*RegionInfo {
r.st.RLock()
defer r.st.RUnlock()
return r.followers[storeID].RandomRegions(randomRegionMaxRetry, ranges)
}

// RandLearnerRegion randomly gets a store's learner region.
func (r *RegionsInfo) RandLearnerRegion(storeID uint64, ranges []KeyRange) *RegionInfo {
r.st.RLock()
defer r.st.RUnlock()
return r.learners[storeID].RandomRegion(ranges)
}

// RandLearnerRegions randomly gets a store's n learner regions.
func (r *RegionsInfo) RandLearnerRegions(storeID uint64, ranges []KeyRange) []*RegionInfo {
r.st.RLock()
defer r.st.RUnlock()
return r.learners[storeID].RandomRegions(randomRegionMaxRetry, ranges)
}

// RandWitnessRegion randomly gets a store's witness region.
func (r *RegionsInfo) RandWitnessRegion(storeID uint64, ranges []KeyRange) *RegionInfo {
r.st.RLock()
defer r.st.RUnlock()
return r.witnesses[storeID].RandomRegion(ranges)
}

// RandWitnessRegions randomly gets a store's n witness regions.
func (r *RegionsInfo) RandWitnessRegions(storeID uint64, ranges []KeyRange) []*RegionInfo {
r.st.RLock()
Expand Down
58 changes: 43 additions & 15 deletions pkg/core/region_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -642,21 +642,49 @@ func BenchmarkUpdateBuckets(b *testing.B) {
}

func BenchmarkRandomRegion(b *testing.B) {
regions := NewRegionsInfo()
for i := 0; i < 5000000; i++ {
peer := &metapb.Peer{StoreId: 1, Id: uint64(i + 1)}
region := NewRegionInfo(&metapb.Region{
Id: uint64(i + 1),
Peers: []*metapb.Peer{peer},
StartKey: []byte(fmt.Sprintf("%20d", i)),
EndKey: []byte(fmt.Sprintf("%20d", i+1)),
}, peer)
origin, overlaps, rangeChanged := regions.SetRegion(region)
regions.UpdateSubTree(region, origin, overlaps, rangeChanged)
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
regions.RandLeaderRegion(1, nil)
for _, size := range []int{10, 100, 1000, 10000, 100000, 1000000, 10000000} {
regions := NewRegionsInfo()
for i := 0; i < size; i++ {
peer := &metapb.Peer{StoreId: 1, Id: uint64(i + 1)}
region := NewRegionInfo(&metapb.Region{
Id: uint64(i + 1),
Peers: []*metapb.Peer{peer},
StartKey: []byte(fmt.Sprintf("%20d", i)),
EndKey: []byte(fmt.Sprintf("%20d", i+1)),
}, peer)
origin, overlaps, rangeChanged := regions.SetRegion(region)
regions.UpdateSubTree(region, origin, overlaps, rangeChanged)
}
b.Run(fmt.Sprintf("random region whole range with size %d", size), func(b *testing.B) {
b.ResetTimer()
for i := 0; i < b.N; i++ {
regions.randLeaderRegion(1, nil)
}
})
b.Run(fmt.Sprintf("random regions whole range with size %d", size), func(b *testing.B) {
b.ResetTimer()
for i := 0; i < b.N; i++ {
regions.RandLeaderRegions(1, nil)
}
})
ranges := []KeyRange{
NewKeyRange(fmt.Sprintf("%20d", 0), fmt.Sprintf("%20d", size/4)),
NewKeyRange(fmt.Sprintf("%20d", size/4), fmt.Sprintf("%20d", size/2)),
NewKeyRange(fmt.Sprintf("%20d", size/2), fmt.Sprintf("%20d", size*3/4)),
NewKeyRange(fmt.Sprintf("%20d", size*3/4), fmt.Sprintf("%20d", size)),
}
b.Run(fmt.Sprintf("random region given ranges with size %d", size), func(b *testing.B) {
b.ResetTimer()
for i := 0; i < b.N; i++ {
regions.randLeaderRegion(1, ranges)
}
})
b.Run(fmt.Sprintf("random regions given ranges with size %d", size), func(b *testing.B) {
b.ResetTimer()
for i := 0; i < b.N; i++ {
regions.RandLeaderRegions(1, ranges)
}
})
}
}

Expand Down
137 changes: 85 additions & 52 deletions pkg/core/region_tree.go
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Original file line number Diff line number Diff line change
Expand Up @@ -52,11 +52,6 @@ func (r *regionItem) Less(other *regionItem) bool {
return bytes.Compare(left, right) < 0
}

func (r *regionItem) Contains(key []byte) bool {
start, end := r.GetStartKey(), r.GetEndKey()
return bytes.Compare(key, start) >= 0 && (len(end) == 0 || bytes.Compare(key, end) < 0)
}

const (
defaultBTreeDegree = 64
)
Expand Down Expand Up @@ -328,62 +323,100 @@ func (t *regionTree) getAdjacentItem(item *regionItem) (prev *regionItem, next *
return prev, next
}

// RandomRegion is used to get a random region within ranges.
func (t *regionTree) RandomRegion(ranges []KeyRange) *RegionInfo {
if t.length() == 0 {
func (t *regionTree) randomRegion(ranges []KeyRange) *RegionInfo {
regions := t.RandomRegions(1, ranges)
if len(regions) == 0 {
return nil
}
return regions[0]
}

if len(ranges) == 0 {
ranges = []KeyRange{NewKeyRange("", "")}
// RandomRegions get n random regions within the given ranges.
func (t *regionTree) RandomRegions(n int, ranges []KeyRange) []*RegionInfo {
treeLen := t.length()
if treeLen == 0 || n < 1 {
return nil
}

for _, i := range rand.Perm(len(ranges)) {
var endIndex int
startKey, endKey := ranges[i].StartKey, ranges[i].EndKey
startRegion, startIndex := t.tree.GetWithIndex(&regionItem{RegionInfo: &RegionInfo{meta: &metapb.Region{StartKey: startKey}}})

if len(endKey) != 0 {
_, endIndex = t.tree.GetWithIndex(&regionItem{RegionInfo: &RegionInfo{meta: &metapb.Region{StartKey: endKey}}})
} else {
endIndex = t.tree.Len()
// Pre-allocate the variables to reduce the temporary memory allocations.
var (
startKey, endKey []byte
startIndex, endIndex, randIndex int
startItem *regionItem
pivotItem = &regionItem{&RegionInfo{meta: &metapb.Region{}}}
region *RegionInfo
regions = make([]*RegionInfo, 0, n)
rangeLen, curLen = len(ranges), len(regions)
// setStartEndIndices is a helper function to set `startIndex` and `endIndex`
// according to the `startKey` and `endKey`.
// TODO: maybe we could cache the `startIndex` and `endIndex` for each range.
setStartEndIndices = func() {
pivotItem.meta.StartKey = startKey
startItem, startIndex = t.tree.GetWithIndex(pivotItem)
if len(endKey) != 0 {
pivotItem.meta.StartKey = endKey
_, endIndex = t.tree.GetWithIndex(pivotItem)
} else {
endIndex = treeLen
}
// Consider that the item in the tree may not be continuous,
// we need to check if the previous item contains the key.
if startIndex != 0 && startItem == nil {
region = t.tree.GetAt(startIndex - 1).RegionInfo
if region.Contains(startKey) {
startIndex--
}
}
}

// Consider that the item in the tree may not be continuous,
// we need to check if the previous item contains the key.
if startIndex != 0 && startRegion == nil && t.tree.GetAt(startIndex-1).Contains(startKey) {
startIndex--
)
// If no ranges specified, select randomly from the whole tree.
// This is a fast path to reduce the unnecessary iterations.
if rangeLen == 0 {
startKey, endKey = []byte(""), []byte("")
setStartEndIndices()
for curLen < n {
randIndex = rand.Intn(endIndex-startIndex) + startIndex
region = t.tree.GetAt(randIndex).RegionInfo
if region.isInvolved(startKey, endKey) {
regions = append(regions, region)
curLen++
}
// No region found, directly break to avoid infinite loop.
if curLen == 0 {
break
}
}
return regions
}
// When there are multiple ranges provided,
// keep retrying until we get enough regions.
for curLen < n {
// Shuffle the ranges to increase the randomness.
for _, i := range rand.Perm(rangeLen) {
startKey, endKey = ranges[i].StartKey, ranges[i].EndKey
setStartEndIndices()
if endIndex <= startIndex {
if len(endKey) > 0 && bytes.Compare(startKey, endKey) > 0 {
log.Error("wrong range keys",
logutil.ZapRedactString("start-key", string(HexRegionKey(startKey))),
logutil.ZapRedactString("end-key", string(HexRegionKey(endKey))),
errs.ZapError(errs.ErrWrongRangeKeys))
}
continue
}

if endIndex <= startIndex {
if len(endKey) > 0 && bytes.Compare(startKey, endKey) > 0 {
log.Error("wrong range keys",
logutil.ZapRedactString("start-key", string(HexRegionKey(startKey))),
logutil.ZapRedactString("end-key", string(HexRegionKey(endKey))),
errs.ZapError(errs.ErrWrongRangeKeys))
randIndex = rand.Intn(endIndex-startIndex) + startIndex
region = t.tree.GetAt(randIndex).RegionInfo
if region.isInvolved(startKey, endKey) {
regions = append(regions, region)
curLen++
if curLen == n {
return regions
}
}
continue
}
index := rand.Intn(endIndex-startIndex) + startIndex
region := t.tree.GetAt(index).RegionInfo
if region.isInvolved(startKey, endKey) {
return region
}
}

return nil
}

func (t *regionTree) RandomRegions(n int, ranges []KeyRange) []*RegionInfo {
if t.length() == 0 {
return nil
}

regions := make([]*RegionInfo, 0, n)

for i := 0; i < n; i++ {
if region := t.RandomRegion(ranges); region != nil {
regions = append(regions, region)
// No region found, directly break to avoid infinite loop.
if curLen == 0 {
break
}
}
return regions
Expand Down
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