*: make hot region scheduler configurable

server/cluster_info.go

@@ -276,14 +276,14 @@ func (c *clusterInfo) GetRegion(regionID uint64) *core.RegionInfo {
 func (c *clusterInfo) IsRegionHot(id uint64) bool {
 	c.RLock()
 	defer c.RUnlock()
-	return c.core.IsRegionHot(id, c.GetHotRegionLowThreshold())
+	return c.core.IsRegionHot(id, c.GetHotRegionCacheHitsThreshold())
 }
 
 // RandHotRegionFromStore randomly picks a hot region in specified store.
 func (c *clusterInfo) RandHotRegionFromStore(store uint64, kind schedule.FlowKind) *core.RegionInfo {
 	c.RLock()
 	defer c.RUnlock()
-	r := c.core.HotCache.RandHotRegionFromStore(store, kind, c.GetHotRegionLowThreshold())
+	r := c.core.HotCache.RandHotRegionFromStore(store, kind, c.GetHotRegionCacheHitsThreshold())
 	if r == nil {
 		return nil
 	}
@@ -636,6 +636,10 @@ func (c *clusterInfo) GetMergeScheduleLimit() uint64 {
 	return c.opt.GetMergeScheduleLimit(namespace.DefaultNamespace)
 }
 
+func (c *clusterInfo) GetHotRegionScheduleLimit() uint64 {
+	return c.opt.GetHotRegionScheduleLimit(namespace.DefaultNamespace)
+}
+
 func (c *clusterInfo) GetTolerantSizeRatio() float64 {
 	return c.opt.GetTolerantSizeRatio()
 }
@@ -684,8 +688,8 @@ func (c *clusterInfo) GetLocationLabels() []string {
 	return c.opt.GetLocationLabels()
 }
 
-func (c *clusterInfo) GetHotRegionLowThreshold() int {
-	return c.opt.GetHotRegionLowThreshold()
+func (c *clusterInfo) GetHotRegionCacheHitsThreshold() int {
+	return c.opt.GetHotRegionCacheHitsThreshold()
 }
 
 func (c *clusterInfo) IsRaftLearnerEnabled() bool {

server/config.go

@@ -456,6 +456,12 @@ type ScheduleConfig struct {
 	ReplicaScheduleLimit uint64 `toml:"replica-schedule-limit,omitempty" json:"replica-schedule-limit"`
 	// MergeScheduleLimit is the max coexist merge schedules.
 	MergeScheduleLimit uint64 `toml:"merge-schedule-limit,omitempty" json:"merge-schedule-limit"`
+	// HotRegionScheduleLimit is the max coexist hot region schedules.
+	HotRegionScheduleLimit uint64 `toml:"hot-region-schedule-limit,omitempty" json:"hot-region-schedule-limit"`
+	// HotRegionCacheHitThreshold is the cache hits threshold of the hot region.
+	// If the number of times a region hits the hot cache is greater than this
+	// threshold, it is considered a hot region.
+	HotRegionCacheHitsThreshold uint64 `toml:"hot-region-cache-hits-threshold,omitempty" json:"hot-region-cache-hits-threshold"`
 	// TolerantSizeRatio is the ratio of buffer size for balance scheduler.
 	TolerantSizeRatio float64 `toml:"tolerant-size-ratio,omitempty" json:"tolerant-size-ratio"`
 	//
@@ -511,6 +517,8 @@ func (c *ScheduleConfig) clone() *ScheduleConfig {
 		RegionScheduleLimit:          c.RegionScheduleLimit,
 		ReplicaScheduleLimit:         c.ReplicaScheduleLimit,
 		MergeScheduleLimit:           c.MergeScheduleLimit,
+		HotRegionScheduleLimit:       c.HotRegionScheduleLimit,
+		HotRegionCacheHitsThreshold:  c.HotRegionCacheHitsThreshold,
 		TolerantSizeRatio:            c.TolerantSizeRatio,
 		LowSpaceRatio:                c.LowSpaceRatio,
 		HighSpaceRatio:               c.HighSpaceRatio,
@@ -526,21 +534,25 @@ func (c *ScheduleConfig) clone() *ScheduleConfig {
 }
 
 const (
-	defaultMaxReplicas          = 3
-	defaultMaxSnapshotCount     = 3
-	defaultMaxPendingPeerCount  = 16
-	defaultMaxMergeRegionSize   = 20
-	defaultMaxMergeRegionKeys   = 200000
-	defaultSplitMergeInterval   = 1 * time.Hour
-	defaultPatrolRegionInterval = 100 * time.Millisecond
-	defaultMaxStoreDownTime     = 30 * time.Minute
-	defaultLeaderScheduleLimit  = 4
-	defaultRegionScheduleLimit  = 4
-	defaultReplicaScheduleLimit = 8
-	defaultMergeScheduleLimit   = 8
-	defaultTolerantSizeRatio    = 5
-	defaultLowSpaceRatio        = 0.8
-	defaultHighSpaceRatio       = 0.6
+	defaultMaxReplicas            = 3
+	defaultMaxSnapshotCount       = 3
+	defaultMaxPendingPeerCount    = 16
+	defaultMaxMergeRegionSize     = 20
+	defaultMaxMergeRegionKeys     = 200000
+	defaultSplitMergeInterval     = 1 * time.Hour
+	defaultPatrolRegionInterval   = 100 * time.Millisecond
+	defaultMaxStoreDownTime       = 30 * time.Minute
+	defaultLeaderScheduleLimit    = 4
+	defaultRegionScheduleLimit    = 4
+	defaultReplicaScheduleLimit   = 8
+	defaultMergeScheduleLimit     = 8
+	defaultHotRegionScheduleLimit = 2
+	defaultTolerantSizeRatio      = 5
+	defaultLowSpaceRatio          = 0.8
+	defaultHighSpaceRatio         = 0.6
+	// defaultHotRegionCacheHitsThreshold is the low hit number threshold of the
+	// hot region.
+	defautHotRegionCacheHitsThreshold = 3
 )
 
 func (c *ScheduleConfig) adjust(meta *configMetaData) error {
@@ -571,6 +583,12 @@ func (c *ScheduleConfig) adjust(meta *configMetaData) error {
 	if !meta.IsDefined("merge-schedule-limit") {
 		adjustUint64(&c.MergeScheduleLimit, defaultMergeScheduleLimit)
 	}
+	if !meta.IsDefined("hot-region-schedule-limit") {
+		adjustUint64(&c.HotRegionScheduleLimit, defaultHotRegionScheduleLimit)
+	}
+	if !meta.IsDefined("hot-region-cache-hits-threshold") {
+		adjustUint64(&c.HotRegionCacheHitsThreshold, defautHotRegionCacheHitsThreshold)
+	}
 	if !meta.IsDefined("tolerant-size-ratio") {
 		adjustFloat64(&c.TolerantSizeRatio, defaultTolerantSizeRatio)
 	}
@@ -670,6 +688,8 @@ type NamespaceConfig struct {
 	ReplicaScheduleLimit uint64 `json:"replica-schedule-limit"`
 	// MergeScheduleLimit is the max coexist merge schedules.
 	MergeScheduleLimit uint64 `json:"merge-schedule-limit"`
+	// HotRegionScheduleLimit is the max coexist hot region schedules.
+	HotRegionScheduleLimit uint64 `json:"hot-region-schedule-limit"`
 	// MaxReplicas is the number of replicas for each region.
 	MaxReplicas uint64 `json:"max-replicas"`
 }
@@ -679,6 +699,7 @@ func (c *NamespaceConfig) adjust(opt *scheduleOption) {
 	adjustUint64(&c.RegionScheduleLimit, opt.GetRegionScheduleLimit(namespace.DefaultNamespace))
 	adjustUint64(&c.ReplicaScheduleLimit, opt.GetReplicaScheduleLimit(namespace.DefaultNamespace))
 	adjustUint64(&c.MergeScheduleLimit, opt.GetMergeScheduleLimit(namespace.DefaultNamespace))
+	adjustUint64(&c.HotRegionScheduleLimit, opt.GetHotRegionScheduleLimit(namespace.DefaultNamespace))
 	adjustUint64(&c.MaxReplicas, uint64(opt.GetMaxReplicas(namespace.DefaultNamespace)))
 }
 

server/option.go

@@ -132,6 +132,13 @@ func (o *scheduleOption) GetMergeScheduleLimit(name string) uint64 {
 	return o.load().MergeScheduleLimit
 }
 
+func (o *scheduleOption) GetHotRegionScheduleLimit(name string) uint64 {
+	if n, ok := o.ns[name]; ok {
+		return n.GetHotRegionScheduleLimit()
+	}
+	return o.load().HotRegionScheduleLimit
+}
+
 func (o *scheduleOption) GetTolerantSizeRatio() float64 {
 	return o.load().TolerantSizeRatio
 }
@@ -341,8 +348,8 @@ func (o *scheduleOption) adjustScheduleCfg(persistentCfg *Config) {
 	o.store(scheduleCfg)
 }
 
-func (o *scheduleOption) GetHotRegionLowThreshold() int {
-	return schedule.HotRegionLowThreshold
+func (o *scheduleOption) GetHotRegionCacheHitsThreshold() int {
+	return int(o.load().HotRegionCacheHitsThreshold)
 }
 
 func (o *scheduleOption) CheckLabelProperty(typ string, labels []*metapb.StoreLabel) bool {
@@ -437,3 +444,8 @@ func (n *namespaceOption) GetReplicaScheduleLimit() uint64 {
 func (n *namespaceOption) GetMergeScheduleLimit() uint64 {
 	return n.load().MergeScheduleLimit
 }
+
+// GetHotRegionScheduleLimit returns the limit for hot region schedule.
+func (n *namespaceOption) GetHotRegionScheduleLimit() uint64 {
+	return n.load().HotRegionScheduleLimit
+}

server/schedule/basic_cluster.go

@@ -17,11 +17,6 @@ import (
 	"github.com/pingcap/pd/server/core"
 )
 
-var (
-	// HotRegionLowThreshold is the low threadshold of hot region
-	HotRegionLowThreshold = 3
-)
-
 const (
 	// RegionHeartBeatReportInterval is the heartbeat report interval of a region
 	RegionHeartBeatReportInterval = 60

server/schedule/mockcluster.go

@@ -60,12 +60,12 @@ func (mc *MockCluster) LoadRegion(regionID uint64, followerIds ...uint64) {
 
 // IsRegionHot checks if the region is hot
 func (mc *MockCluster) IsRegionHot(id uint64) bool {
-	return mc.BasicCluster.IsRegionHot(id, mc.GetHotRegionLowThreshold())
+	return mc.BasicCluster.IsRegionHot(id, mc.GetHotRegionCacheHitsThreshold())
 }
 
 // RandHotRegionFromStore random picks a hot region in specify store.
 func (mc *MockCluster) RandHotRegionFromStore(store uint64, kind FlowKind) *core.RegionInfo {
-	r := mc.HotCache.RandHotRegionFromStore(store, kind, mc.GetHotRegionLowThreshold())
+	r := mc.HotCache.RandHotRegionFromStore(store, kind, mc.GetHotRegionCacheHitsThreshold())
 	if r == nil {
 		return nil
 	}
@@ -399,6 +399,11 @@ func (mc *MockCluster) GetMergeScheduleLimit() uint64 {
 	return mc.MockSchedulerOptions.GetMergeScheduleLimit(namespace.DefaultNamespace)
 }
 
+// GetHotRegionScheduleLimit mocks method.
+func (mc *MockCluster) GetHotRegionScheduleLimit() uint64 {
+	return mc.MockSchedulerOptions.GetHotRegionScheduleLimit(namespace.DefaultNamespace)
+}
+
 // GetMaxReplicas mocks method.
 func (mc *MockCluster) GetMaxReplicas() int {
 	return mc.MockSchedulerOptions.GetMaxReplicas(namespace.DefaultNamespace)
@@ -417,20 +422,22 @@ func (mc *MockCluster) CheckLabelProperty(typ string, labels []*metapb.StoreLabe
 }
 
 const (
-	defaultMaxReplicas          = 3
-	defaultMaxSnapshotCount     = 3
-	defaultMaxPendingPeerCount  = 16
-	defaultMaxMergeRegionSize   = 0
-	defaultMaxMergeRegionKeys   = 0
-	defaultSplitMergeInterval   = 0
-	defaultMaxStoreDownTime     = 30 * time.Minute
-	defaultLeaderScheduleLimit  = 4
-	defaultRegionScheduleLimit  = 4
-	defaultReplicaScheduleLimit = 8
-	defaultMergeScheduleLimit   = 8
-	defaultTolerantSizeRatio    = 2.5
-	defaultLowSpaceRatio        = 0.8
-	defaultHighSpaceRatio       = 0.6
+	defaultMaxReplicas                 = 3
+	defaultMaxSnapshotCount            = 3
+	defaultMaxPendingPeerCount         = 16
+	defaultMaxMergeRegionSize          = 0
+	defaultMaxMergeRegionKeys          = 0
+	defaultSplitMergeInterval          = 0
+	defaultMaxStoreDownTime            = 30 * time.Minute
+	defaultLeaderScheduleLimit         = 4
+	defaultRegionScheduleLimit         = 4
+	defaultReplicaScheduleLimit        = 8
+	defaultMergeScheduleLimit          = 8
+	defaultHotRegionScheduleLimit      = 2
+	defaultTolerantSizeRatio           = 2.5
+	defaultLowSpaceRatio               = 0.8
+	defaultHighSpaceRatio              = 0.6
+	defaultHotRegionCacheHitsThreshold = 3
 )
 
 // MockSchedulerOptions is a mock of SchedulerOptions
@@ -440,6 +447,7 @@ type MockSchedulerOptions struct {
 	LeaderScheduleLimit          uint64
 	ReplicaScheduleLimit         uint64
 	MergeScheduleLimit           uint64
+	HotRegionScheduleLimit       uint64
 	MaxSnapshotCount             uint64
 	MaxPendingPeerCount          uint64
 	MaxMergeRegionSize           uint64
@@ -448,7 +456,7 @@ type MockSchedulerOptions struct {
 	MaxStoreDownTime             time.Duration
 	MaxReplicas                  int
 	LocationLabels               []string
-	HotRegionLowThreshold        int
+	HotRegionCacheHitsThreshold  int
 	TolerantSizeRatio            float64
 	LowSpaceRatio                float64
 	HighSpaceRatio               float64
@@ -469,13 +477,14 @@ func NewMockSchedulerOptions() *MockSchedulerOptions {
 	mso.LeaderScheduleLimit = defaultLeaderScheduleLimit
 	mso.ReplicaScheduleLimit = defaultReplicaScheduleLimit
 	mso.MergeScheduleLimit = defaultMergeScheduleLimit
+	mso.HotRegionScheduleLimit = defaultHotRegionScheduleLimit
 	mso.MaxSnapshotCount = defaultMaxSnapshotCount
 	mso.MaxMergeRegionSize = defaultMaxMergeRegionSize
 	mso.MaxMergeRegionKeys = defaultMaxMergeRegionKeys
 	mso.SplitMergeInterval = defaultSplitMergeInterval
 	mso.MaxStoreDownTime = defaultMaxStoreDownTime
 	mso.MaxReplicas = defaultMaxReplicas
-	mso.HotRegionLowThreshold = HotRegionLowThreshold
+	mso.HotRegionCacheHitsThreshold = defaultHotRegionCacheHitsThreshold
 	mso.MaxPendingPeerCount = defaultMaxPendingPeerCount
 	mso.TolerantSizeRatio = defaultTolerantSizeRatio
 	mso.LowSpaceRatio = defaultLowSpaceRatio
@@ -503,6 +512,11 @@ func (mso *MockSchedulerOptions) GetMergeScheduleLimit(name string) uint64 {
 	return mso.MergeScheduleLimit
 }
 
+// GetHotRegionScheduleLimit mock method
+func (mso *MockSchedulerOptions) GetHotRegionScheduleLimit(name string) uint64 {
+	return mso.HotRegionScheduleLimit
+}
+
 // GetMaxSnapshotCount mock method
 func (mso *MockSchedulerOptions) GetMaxSnapshotCount() uint64 {
 	return mso.MaxSnapshotCount
@@ -543,9 +557,9 @@ func (mso *MockSchedulerOptions) GetLocationLabels() []string {
 	return mso.LocationLabels
 }
 
-// GetHotRegionLowThreshold mock method
-func (mso *MockSchedulerOptions) GetHotRegionLowThreshold() int {
-	return mso.HotRegionLowThreshold
+// GetHotRegionCacheHitsThreshold mock method
+func (mso *MockSchedulerOptions) GetHotRegionCacheHitsThreshold() int {
+	return mso.HotRegionCacheHitsThreshold
 }
 
 // GetTolerantSizeRatio mock method

server/schedule/opts.go

@@ -29,6 +29,7 @@ type Options interface {
 	GetRegionScheduleLimit() uint64
 	GetReplicaScheduleLimit() uint64
 	GetMergeScheduleLimit() uint64
+	GetHotRegionScheduleLimit() uint64
 
 	GetMaxSnapshotCount() uint64
 	GetMaxPendingPeerCount() uint64
@@ -40,7 +41,7 @@ type Options interface {
 	GetMaxReplicas() int
 	GetLocationLabels() []string
 
-	GetHotRegionLowThreshold() int
+	GetHotRegionCacheHitsThreshold() int
 	GetTolerantSizeRatio() float64
 	GetLowSpaceRatio() float64
 	GetHighSpaceRatio() float64

server/schedulers/balance_test.go

@@ -1098,7 +1098,7 @@ func (s *testBalanceHotWriteRegionSchedulerSuite) TestBalance(c *C) {
 	tc.AddLeaderRegionWithWriteInfo(1, 1, 512*1024*schedule.RegionHeartBeatReportInterval, 2, 3)
 	tc.AddLeaderRegionWithWriteInfo(2, 1, 512*1024*schedule.RegionHeartBeatReportInterval, 3, 4)
 	tc.AddLeaderRegionWithWriteInfo(3, 1, 512*1024*schedule.RegionHeartBeatReportInterval, 2, 4)
-	opt.HotRegionLowThreshold = 0
+	opt.HotRegionCacheHitsThreshold = 0
 
 	// Will transfer a hot region from store 1, because the total count of peers
 	// which is hot for store 1 is more larger than other stores.
@@ -1193,7 +1193,7 @@ func (s *testBalanceHotReadRegionSchedulerSuite) TestBalance(c *C) {
 	tc.AddLeaderRegionWithReadInfo(3, 1, 512*1024*schedule.RegionHeartBeatReportInterval, 2, 3)
 	// lower than hot read flow rate, but higher than write flow rate
 	tc.AddLeaderRegionWithReadInfo(11, 1, 24*1024*schedule.RegionHeartBeatReportInterval, 2, 3)
-	opt.HotRegionLowThreshold = 0
+	opt.HotRegionCacheHitsThreshold = 0
 	c.Assert(tc.IsRegionHot(1), IsTrue)
 	c.Assert(tc.IsRegionHot(11), IsFalse)
 	// check randomly pick hot region

server/schedulers/hot_region.go

@@ -122,13 +122,20 @@ func (h *balanceHotRegionsScheduler) IsScheduleAllowed(cluster schedule.Cluster)
 	return h.allowBalanceLeader(cluster) || h.allowBalanceRegion(cluster)
 }
 
+func min(a, b uint64) uint64 {
+	if a < b {
+		return a
+	}
+	return b
+}
+
 func (h *balanceHotRegionsScheduler) allowBalanceLeader(cluster schedule.Cluster) bool {
-	return h.opController.OperatorCount(schedule.OpHotRegion) < h.limit &&
+	return h.opController.OperatorCount(schedule.OpHotRegion) < min(h.limit, cluster.GetHotRegionScheduleLimit()) &&
 		h.opController.OperatorCount(schedule.OpLeader) < cluster.GetLeaderScheduleLimit()
 }
 
 func (h *balanceHotRegionsScheduler) allowBalanceRegion(cluster schedule.Cluster) bool {
-	return h.opController.OperatorCount(schedule.OpHotRegion) < h.limit &&
+	return h.opController.OperatorCount(schedule.OpHotRegion) < min(h.limit, cluster.GetHotRegionScheduleLimit()) &&
 		h.opController.OperatorCount(schedule.OpRegion) < cluster.GetRegionScheduleLimit()
 }
 
@@ -205,7 +212,7 @@ func calcScore(items []*core.RegionStat, cluster schedule.Cluster, kind core.Res
 		// HotDegree is the update times on the hot cache. If the heartbeat report
 		// the flow of the region exceeds the threshold, the scheduler will update the region in
 		// the hot cache and the hotdegree of the region will increase.
-		if r.HotDegree < cluster.GetHotRegionLowThreshold() {
+		if r.HotDegree < cluster.GetHotRegionCacheHitsThreshold() {
 			continue
 		}
 

server/schedulers/scheduler_test.go

@@ -311,7 +311,7 @@ func (s *testShuffleHotRegionSchedulerSuite) TestBalance(c *C) {
 	tc.AddLeaderRegionWithWriteInfo(1, 1, 512*1024*schedule.RegionHeartBeatReportInterval, 2, 3)
 	tc.AddLeaderRegionWithWriteInfo(2, 1, 512*1024*schedule.RegionHeartBeatReportInterval, 3, 4)
 	tc.AddLeaderRegionWithWriteInfo(3, 1, 512*1024*schedule.RegionHeartBeatReportInterval, 2, 4)
-	opt.HotRegionLowThreshold = 0
+	opt.HotRegionCacheHitsThreshold = 0
 
 	// try to get an operator
 	var op []*schedule.Operator

server/server.go

@@ -572,10 +572,12 @@ func (s *Server) GetNamespaceConfig(name string) *NamespaceConfig {
 	}
 
 	cfg := &NamespaceConfig{
-		LeaderScheduleLimit:  s.scheduleOpt.GetLeaderScheduleLimit(name),
-		RegionScheduleLimit:  s.scheduleOpt.GetRegionScheduleLimit(name),
-		ReplicaScheduleLimit: s.scheduleOpt.GetReplicaScheduleLimit(name),
-		MaxReplicas:          uint64(s.scheduleOpt.GetMaxReplicas(name)),
+		LeaderScheduleLimit:    s.scheduleOpt.GetLeaderScheduleLimit(name),
+		RegionScheduleLimit:    s.scheduleOpt.GetRegionScheduleLimit(name),
+		ReplicaScheduleLimit:   s.scheduleOpt.GetReplicaScheduleLimit(name),
+		HotRegionScheduleLimit: s.scheduleOpt.GetHotRegionScheduleLimit(name),
+		MergeScheduleLimit:     s.scheduleOpt.GetMergeScheduleLimit(name),
+		MaxReplicas:            uint64(s.scheduleOpt.GetMaxReplicas(name)),
 	}
 
 	return cfg