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balance_region.go
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balance_region.go
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// Copyright 2017 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package schedulers
import (
"fmt"
"strconv"
"github.com/pingcap/kvproto/pkg/metapb"
"github.com/pingcap/pd/server/cache"
"github.com/pingcap/pd/server/core"
"github.com/pingcap/pd/server/schedule"
log "github.com/sirupsen/logrus"
)
func init() {
schedule.RegisterScheduler("balance-region", func(limiter *schedule.Limiter, args []string) (schedule.Scheduler, error) {
return newBalanceRegionScheduler(limiter), nil
})
}
// balanceRegionRetryLimit is the limit to retry schedule for selected store.
const balanceRegionRetryLimit = 10
type balanceRegionScheduler struct {
*baseScheduler
selector schedule.Selector
taintStores *cache.TTLUint64
}
// newBalanceRegionScheduler creates a scheduler that tends to keep regions on
// each store balanced.
func newBalanceRegionScheduler(limiter *schedule.Limiter) schedule.Scheduler {
taintStores := newTaintCache()
filters := []schedule.Filter{
schedule.NewCacheFilter(taintStores),
schedule.NewStateFilter(),
schedule.NewHealthFilter(),
schedule.NewSnapshotCountFilter(),
schedule.NewPendingPeerCountFilter(),
}
base := newBaseScheduler(limiter)
return &balanceRegionScheduler{
baseScheduler: base,
selector: schedule.NewBalanceSelector(core.RegionKind, filters),
taintStores: taintStores,
}
}
func (s *balanceRegionScheduler) GetName() string {
return "balance-region-scheduler"
}
func (s *balanceRegionScheduler) GetType() string {
return "balance-region"
}
func (s *balanceRegionScheduler) IsScheduleAllowed(cluster schedule.Cluster) bool {
return s.limiter.OperatorCount(schedule.OpRegion) < cluster.GetRegionScheduleLimit()
}
func (s *balanceRegionScheduler) Schedule(cluster schedule.Cluster, opInfluence schedule.OpInfluence) []*schedule.Operator {
schedulerCounter.WithLabelValues(s.GetName(), "schedule").Inc()
stores := cluster.GetStores()
// source is the store with highest region score in the list that can be selected as balance source.
source := s.selector.SelectSource(cluster, stores)
if source == nil {
schedulerCounter.WithLabelValues(s.GetName(), "no_store").Inc()
// Unlike the balanceLeaderScheduler, we don't need to clear the taintCache
// here. Because normally region score won't change rapidly, and the region
// balance requires lower sensitivity compare to leader balance.
return nil
}
log.Debugf("[%s] store%d has the max region score", s.GetName(), source.GetId())
sourceLabel := strconv.FormatUint(source.GetId(), 10)
balanceRegionCounter.WithLabelValues("source_store", sourceLabel).Inc()
for i := 0; i < balanceRegionRetryLimit; i++ {
region := cluster.RandFollowerRegion(source.GetId(), core.HealthRegion())
if region == nil {
region = cluster.RandLeaderRegion(source.GetId(), core.HealthRegion())
}
if region == nil {
schedulerCounter.WithLabelValues(s.GetName(), "no_region").Inc()
continue
}
log.Debugf("[%s] select region%d", s.GetName(), region.GetId())
// We don't schedule region with abnormal number of replicas.
if len(region.GetPeers()) != cluster.GetMaxReplicas() {
log.Debugf("[%s] region%d has abnormal replica count", s.GetName(), region.GetId())
schedulerCounter.WithLabelValues(s.GetName(), "abnormal_replica").Inc()
continue
}
// Skip hot regions.
if cluster.IsRegionHot(region.GetId()) {
log.Debugf("[%s] region%d is hot", s.GetName(), region.GetId())
schedulerCounter.WithLabelValues(s.GetName(), "region_hot").Inc()
continue
}
oldPeer := region.GetStorePeer(source.GetId())
if op := s.transferPeer(cluster, region, oldPeer, opInfluence); op != nil {
schedulerCounter.WithLabelValues(s.GetName(), "new_operator").Inc()
return []*schedule.Operator{op}
}
}
// If no operator can be created for the selected store, ignore it for a while.
log.Debugf("[%s] no operator created for selected store%d", s.GetName(), source.GetId())
balanceRegionCounter.WithLabelValues("add_taint", sourceLabel).Inc()
s.taintStores.Put(source.GetId())
return nil
}
func (s *balanceRegionScheduler) transferPeer(cluster schedule.Cluster, region *core.RegionInfo, oldPeer *metapb.Peer, opInfluence schedule.OpInfluence) *schedule.Operator {
// scoreGuard guarantees that the distinct score will not decrease.
stores := cluster.GetRegionStores(region)
source := cluster.GetStore(oldPeer.GetStoreId())
scoreGuard := schedule.NewDistinctScoreFilter(cluster.GetLocationLabels(), stores, source)
checker := schedule.NewReplicaChecker(cluster, nil)
storeID, _ := checker.SelectBestReplacementStore(region, oldPeer, scoreGuard)
if storeID == 0 {
schedulerCounter.WithLabelValues(s.GetName(), "no_replacement").Inc()
return nil
}
target := cluster.GetStore(storeID)
log.Debugf("[region %d] source store id is %v, target store id is %v", region.GetId(), source.GetId(), target.GetId())
if !shouldBalance(cluster, source, target, core.RegionKind, region, opInfluence) {
log.Debugf(`[%s] skip balance region %d, source %d to target %d ,source size: %v, source score: %v, source influence: %v,
target size: %v, target score: %v, target influence: %v, region size: %v`, s.GetName(), region.GetId(), source.GetId(), target.GetId(),
source.RegionSize, source.RegionScore(cluster.GetHighSpaceRatio(), cluster.GetLowSpaceRatio(), 0),
opInfluence.GetStoreInfluence(source.GetId()).ResourceSize(core.RegionKind),
target.RegionSize, target.RegionScore(cluster.GetHighSpaceRatio(), cluster.GetLowSpaceRatio(), 0),
opInfluence.GetStoreInfluence(target.GetId()).ResourceSize(core.RegionKind),
region.ApproximateSize)
schedulerCounter.WithLabelValues(s.GetName(), "skip").Inc()
return nil
}
newPeer, err := cluster.AllocPeer(storeID)
if err != nil {
schedulerCounter.WithLabelValues(s.GetName(), "no_peer").Inc()
return nil
}
balanceRegionCounter.WithLabelValues("move_peer", fmt.Sprintf("store%d-out", source.GetId())).Inc()
balanceRegionCounter.WithLabelValues("move_peer", fmt.Sprintf("store%d-in", target.GetId())).Inc()
return schedule.CreateMovePeerOperator("balance-region", cluster, region, schedule.OpBalance, oldPeer.GetStoreId(), newPeer.GetStoreId(), newPeer.GetId())
}