forked from tikv/pd
/
balance_leader.go
175 lines (153 loc) · 7.27 KB
/
balance_leader.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/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-leader", func(limiter *schedule.Limiter, args []string) (schedule.Scheduler, error) {
return newBalanceLeaderScheduler(limiter), nil
})
}
// balanceLeaderRetryLimit is the limit to retry schedule for selected source store and target store.
const balanceLeaderRetryLimit = 10
type balanceLeaderScheduler struct {
*baseScheduler
selector schedule.Selector
taintStores *cache.TTLUint64
}
// newBalanceLeaderScheduler creates a scheduler that tends to keep leaders on
// each store balanced.
func newBalanceLeaderScheduler(limiter *schedule.Limiter) schedule.Scheduler {
taintStores := newTaintCache()
filters := []schedule.Filter{
schedule.NewBlockFilter(),
schedule.NewStateFilter(),
schedule.NewHealthFilter(),
schedule.NewDisconnectFilter(),
schedule.NewRejectLeaderFilter(),
schedule.NewCacheFilter(taintStores),
}
base := newBaseScheduler(limiter)
return &balanceLeaderScheduler{
baseScheduler: base,
selector: schedule.NewBalanceSelector(core.LeaderKind, filters),
taintStores: taintStores,
}
}
func (l *balanceLeaderScheduler) GetName() string {
return "balance-leader-scheduler"
}
func (l *balanceLeaderScheduler) GetType() string {
return "balance-leader"
}
func (l *balanceLeaderScheduler) IsScheduleAllowed(cluster schedule.Cluster) bool {
return l.limiter.OperatorCount(schedule.OpLeader) < cluster.GetLeaderScheduleLimit()
}
func (l *balanceLeaderScheduler) Schedule(cluster schedule.Cluster, opInfluence schedule.OpInfluence) []*schedule.Operator {
schedulerCounter.WithLabelValues(l.GetName(), "schedule").Inc()
stores := cluster.GetStores()
// source/target is the store with highest/lowest leader score in the list that
// can be selected as balance source/target.
source := l.selector.SelectSource(cluster, stores)
target := l.selector.SelectTarget(cluster, stores)
// No store can be selected as source or target.
if source == nil || target == nil {
schedulerCounter.WithLabelValues(l.GetName(), "no_store").Inc()
// When the cluster is balanced, all stores will be added to the cache once
// all of them have been selected. This will cause the scheduler to not adapt
// to sudden change of a store's leader. Here we clear the taint cache and
// re-iterate.
l.taintStores.Clear()
return nil
}
log.Debugf("[%s] store%d has the max leader score, store%d has the min leader score", l.GetName(), source.GetId(), target.GetId())
sourceStoreLabel := strconv.FormatUint(source.GetId(), 10)
targetStoreLabel := strconv.FormatUint(target.GetId(), 10)
balanceLeaderCounter.WithLabelValues("high_score", sourceStoreLabel).Inc()
balanceLeaderCounter.WithLabelValues("low_score", targetStoreLabel).Inc()
for i := 0; i < balanceLeaderRetryLimit; i++ {
if op := l.transferLeaderOut(source, cluster, opInfluence); op != nil {
balanceLeaderCounter.WithLabelValues("transfer_out", sourceStoreLabel).Inc()
return op
}
if op := l.transferLeaderIn(target, cluster, opInfluence); op != nil {
balanceLeaderCounter.WithLabelValues("transfer_in", targetStoreLabel).Inc()
return op
}
}
// If no operator can be created for the selected stores, ignore them for a while.
log.Debugf("[%s] no operator created for selected store%d and store%d", l.GetName(), source.GetId(), target.GetId())
balanceLeaderCounter.WithLabelValues("add_taint", strconv.FormatUint(source.GetId(), 10)).Inc()
l.taintStores.Put(source.GetId())
balanceLeaderCounter.WithLabelValues("add_taint", strconv.FormatUint(target.GetId(), 10)).Inc()
l.taintStores.Put(target.GetId())
return nil
}
func (l *balanceLeaderScheduler) transferLeaderOut(source *core.StoreInfo, cluster schedule.Cluster, opInfluence schedule.OpInfluence) []*schedule.Operator {
region := cluster.RandLeaderRegion(source.GetId(), core.HealthRegion())
if region == nil {
log.Debugf("[%s] store%d has no leader", l.GetName(), source.GetId())
schedulerCounter.WithLabelValues(l.GetName(), "no_leader_region").Inc()
return nil
}
target := l.selector.SelectTarget(cluster, cluster.GetFollowerStores(region))
if target == nil {
log.Debugf("[%s] region %d has no target store", l.GetName(), region.GetId())
schedulerCounter.WithLabelValues(l.GetName(), "no_target_store").Inc()
return nil
}
return l.createOperator(region, source, target, cluster, opInfluence)
}
func (l *balanceLeaderScheduler) transferLeaderIn(target *core.StoreInfo, cluster schedule.Cluster, opInfluence schedule.OpInfluence) []*schedule.Operator {
region := cluster.RandFollowerRegion(target.GetId(), core.HealthRegion())
if region == nil {
log.Debugf("[%s] store%d has no follower", l.GetName(), target.GetId())
schedulerCounter.WithLabelValues(l.GetName(), "no_follower_region").Inc()
return nil
}
source := cluster.GetStore(region.Leader.GetStoreId())
if source == nil {
log.Debugf("[%s] region %d has no leader", l.GetName(), region.GetId())
schedulerCounter.WithLabelValues(l.GetName(), "no_leader").Inc()
return nil
}
return l.createOperator(region, source, target, cluster, opInfluence)
}
func (l *balanceLeaderScheduler) createOperator(region *core.RegionInfo, source, target *core.StoreInfo, cluster schedule.Cluster, opInfluence schedule.OpInfluence) []*schedule.Operator {
if cluster.IsRegionHot(region.GetId()) {
log.Debugf("[%s] region %d is hot region, ignore it", l.GetName(), region.GetId())
schedulerCounter.WithLabelValues(l.GetName(), "region_hot").Inc()
return nil
}
if !shouldBalance(cluster, source, target, core.LeaderKind, 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`, l.GetName(), region.GetId(), source.GetId(), target.GetId(),
source.LeaderSize, source.LeaderScore(0), opInfluence.GetStoreInfluence(source.GetId()).ResourceSize(core.LeaderKind),
target.LeaderSize, target.LeaderScore(0), opInfluence.GetStoreInfluence(target.GetId()).ResourceSize(core.LeaderKind),
region.ApproximateSize)
schedulerCounter.WithLabelValues(l.GetName(), "skip").Inc()
return nil
}
schedulerCounter.WithLabelValues(l.GetName(), "new_operator").Inc()
balanceLeaderCounter.WithLabelValues("move_leader", fmt.Sprintf("store%d-out", source.GetId())).Inc()
balanceLeaderCounter.WithLabelValues("move_leader", fmt.Sprintf("store%d-in", target.GetId())).Inc()
step := schedule.TransferLeader{FromStore: region.Leader.GetStoreId(), ToStore: target.GetId()}
op := schedule.NewOperator("balance-leader", region.GetId(), region.GetRegionEpoch(), schedule.OpBalance|schedule.OpLeader, step)
return []*schedule.Operator{op}
}