api: add a new scheduler to balance the regions of the given key range

pkg/core/basic_cluster.go

@@ -16,6 +16,7 @@ package core
 
 import (
 	"bytes"
+	"encoding/json"
 
 	"github.com/tikv/pd/pkg/core/constant"
 )
@@ -156,6 +157,15 @@ type KeyRange struct {
 	EndKey   []byte `json:"end-key"`
 }
 
+// MarshalJSON marshals to json.
+func (kr KeyRange) MarshalJSON() ([]byte, error) {
+	m := map[string]string{
+		"start-key": HexRegionKeyStr(kr.StartKey),
+		"end-key":   HexRegionKeyStr(kr.EndKey),
+	}
+	return json.Marshal(m)
+}
+
 // NewKeyRange create a KeyRange with the given start key and end key.
 func NewKeyRange(startKey, endKey string) KeyRange {
 	return KeyRange{

pkg/mcs/scheduling/server/cluster.go

@@ -328,7 +328,11 @@
 		)
 		// Create the newly added schedulers.
 		for _, scheduler := range latestSchedulersConfig {
-			schedulerType := types.ConvertOldStrToType[scheduler.Type]
+			schedulerType, ok := types.ConvertOldStrToType[scheduler.Type]
+			if !ok {
+				log.Error("scheduler not found", zap.String("type", scheduler.Type))
+				continue
+			}
 			s, err := schedulers.CreateScheduler(
 				schedulerType,
 				c.coordinator.GetOperatorController(),

pkg/schedule/config/config_provider.go

@@ -39,12 +39,6 @@ func RegisterScheduler(typ types.CheckerSchedulerType) {
 	schedulerMap.Store(typ, struct{}{})
 }
 
-// IsSchedulerRegistered checks if the named scheduler type is registered.
-func IsSchedulerRegistered(typ types.CheckerSchedulerType) bool {
-	_, ok := schedulerMap.Load(typ)
-	return ok
-}
-
 // SchedulerConfigProvider is the interface for scheduler configurations.
 type SchedulerConfigProvider interface {
 	SharedConfigProvider

pkg/schedule/schedulers/balance_range.go

@@ -0,0 +1,237 @@
+// Copyright 2025 TiKV Project Authors.
+//
+// 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,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package schedulers
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/gorilla/mux"
+	"github.com/unrolled/render"
+
+	"github.com/pingcap/log"
+
+	"github.com/tikv/pd/pkg/core"
+	"github.com/tikv/pd/pkg/core/constant"
+	"github.com/tikv/pd/pkg/errs"
+	sche "github.com/tikv/pd/pkg/schedule/core"
+	"github.com/tikv/pd/pkg/schedule/filter"
+	"github.com/tikv/pd/pkg/schedule/operator"
+	"github.com/tikv/pd/pkg/schedule/plan"
+	"github.com/tikv/pd/pkg/schedule/types"
+	"github.com/tikv/pd/pkg/utils/syncutil"
+)
+
+type balanceRangeSchedulerHandler struct {
+	rd     *render.Render
+	config *balanceRangeSchedulerConfig
+}
+
+func newBalanceRangeHandler(conf *balanceRangeSchedulerConfig) http.Handler {
+	handler := &balanceRangeSchedulerHandler{
+		config: conf,
+		rd:     render.New(render.Options{IndentJSON: true}),
+	}
+	router := mux.NewRouter()
+	router.HandleFunc("/config", handler.updateConfig).Methods(http.MethodPost)
+	router.HandleFunc("/list", handler.listConfig).Methods(http.MethodGet)
+	return router
+}
+
+func (handler *balanceRangeSchedulerHandler) updateConfig(w http.ResponseWriter, _ *http.Request) {
+	handler.rd.JSON(w, http.StatusBadRequest, "update config is not supported")
+}
+
+func (handler *balanceRangeSchedulerHandler) listConfig(w http.ResponseWriter, _ *http.Request) {
+	conf := handler.config.clone()
+	if err := handler.rd.JSON(w, http.StatusOK, conf); err != nil {
+		log.Error("failed to marshal balance key range scheduler config", errs.ZapError(err))
+	}
+}
+
+type balanceRangeSchedulerConfig struct {
+	syncutil.RWMutex
+	schedulerConfig
+	jobs []*balanceRangeSchedulerJob
+}
+
+type balanceRangeSchedulerJob struct {
+	JobID   uint64          `json:"job-id"`
+	Role    Role            `json:"role"`
+	Engine  string          `json:"engine"`
+	Timeout time.Duration   `json:"timeout"`
+	Ranges  []core.KeyRange `json:"ranges"`
+	Alias   string          `json:"alias"`
+	Status  JobStatus       `json:"status"`
+}
+
+func (conf *balanceRangeSchedulerConfig) clone() []*balanceRangeSchedulerJob {
+	conf.RLock()
+	defer conf.RUnlock()
+	jobs := make([]*balanceRangeSchedulerJob, 0, len(conf.jobs))
+	for _, job := range conf.jobs {
+		ranges := make([]core.KeyRange, len(job.Ranges))
+		copy(ranges, job.Ranges)
+		jobs = append(jobs, &balanceRangeSchedulerJob{
+			Ranges:  ranges,
+			Role:    job.Role,
+			Engine:  job.Engine,
+			Timeout: job.Timeout,
+			Alias:   job.Alias,
+			JobID:   job.JobID,
+		})
+	}
+
+	return jobs
+}
+
+// EncodeConfig serializes the config.
+func (s *balanceRangeScheduler) EncodeConfig() ([]byte, error) {
+	s.conf.RLock()
+	defer s.conf.RUnlock()
+	return EncodeConfig(s.conf.jobs)
+}
+
+// ReloadConfig reloads the config.
+func (s *balanceRangeScheduler) ReloadConfig() error {
+	s.conf.Lock()
+	defer s.conf.Unlock()
+
+	jobs := make([]*balanceRangeSchedulerJob, 0, len(s.conf.jobs))
+	if err := s.conf.load(jobs); err != nil {
+		return err
+	}
+	s.conf.jobs = jobs
+	return nil
+}
+
+type balanceRangeScheduler struct {
+	*BaseScheduler
+	conf          *balanceRangeSchedulerConfig
+	handler       http.Handler
+	filters       []filter.Filter
+	filterCounter *filter.Counter
+}
+
+// ServeHTTP implements the http.Handler interface.
+func (s *balanceRangeScheduler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	s.handler.ServeHTTP(w, r)
+}
+
+// Schedule schedules the balance key range operator.
+func (*balanceRangeScheduler) Schedule(_cluster sche.SchedulerCluster, _dryRun bool) ([]*operator.Operator, []plan.Plan) {
+	log.Debug("balance key range scheduler is scheduling, need to implement")
+	return nil, nil
+}
+
+// IsScheduleAllowed checks if the scheduler is allowed to schedule new operators.
+func (s *balanceRangeScheduler) IsScheduleAllowed(cluster sche.SchedulerCluster) bool {
+	allowed := s.OpController.OperatorCount(operator.OpRange) < cluster.GetSchedulerConfig().GetRegionScheduleLimit()
+	if !allowed {
+		operator.IncOperatorLimitCounter(s.GetType(), operator.OpRange)
+	}
+	return allowed
+}
+
+// BalanceRangeCreateOption is used to create a scheduler with an option.
+type BalanceRangeCreateOption func(s *balanceRangeScheduler)
+
+// newBalanceRangeScheduler creates a scheduler that tends to keep given peer Role on
+// special store balanced.
+func newBalanceRangeScheduler(opController *operator.Controller, conf *balanceRangeSchedulerConfig, options ...BalanceRangeCreateOption) Scheduler {
+	s := &balanceRangeScheduler{
+		BaseScheduler: NewBaseScheduler(opController, types.BalanceRangeScheduler, conf),
+		conf:          conf,
+		handler:       newBalanceRangeHandler(conf),
+	}
+	for _, option := range options {
+		option(s)
+	}
+	s.filters = []filter.Filter{
+		&filter.StoreStateFilter{ActionScope: s.GetName(), TransferLeader: true, OperatorLevel: constant.Medium},
+		filter.NewSpecialUseFilter(s.GetName()),
+	}
+	s.filterCounter = filter.NewCounter(s.GetName())
+	return s
+}
+
+// JobStatus is the status of the job.
+type JobStatus int
+
+const (
+	pending JobStatus = iota
+	running
+	finished
+)
+
+func (s JobStatus) String() string {
+	switch s {
+	case pending:
+		return "pending"
+	case running:
+		return "running"
+	case finished:
+		return "finished"
+	}
+	return "unknown"
+}
+
+// MarshalJSON marshals to json.
+func (s JobStatus) MarshalJSON() ([]byte, error) {
+	return []byte(`"` + s.String() + `"`), nil
+}
+
+// Role is the role of the region.
+type Role int
+
+const (
+	leader Role = iota
+	// include leader + voter
+	follower
+	learner
+	unknown
+)
+
+// NewRole creates a new role.
+func NewRole(role string) Role {
+	switch role {
+	case "leader":
+		return leader
+	case "follower":
+		return follower
+	case "learner":
+		return learner
+	default:
+		return unknown
+	}
+}
+
+func (r Role) String() string {
+	switch r {
+	case leader:
+		return "leader"
+	case follower:
+		return "follower"
+	case learner:
+		return "learner"
+	default:
+		return "unknown"
+	}
+}
+
+// MarshalJSON marshals to json.
+func (r Role) MarshalJSON() ([]byte, error) {
+	return []byte(`"` + r.String() + `"`), nil
+}

pkg/schedule/schedulers/init.go

@@ -15,9 +15,11 @@
 package schedulers
 
 import (
+	"net/url"
 	"strconv"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/tikv/pd/pkg/core"
 	"github.com/tikv/pd/pkg/errs"
@@ -545,4 +547,76 @@
 		conf.init(sche.GetName(), storage, conf)
 		return sche, nil
 	})
+
+	// balance key range scheduler
+	// args: [role, engine, timeout, alias, range1, range2, ...]
+	RegisterSliceDecoderBuilder(types.BalanceRangeScheduler, func(args []string) ConfigDecoder {
+		return func(v any) error {
+			conf, ok := v.(*balanceRangeSchedulerConfig)
+			if !ok {
+				return errs.ErrScheduleConfigNotExist.FastGenByArgs()
+			}
+			if len(args) < 5 {
+				return errs.ErrSchedulerConfig.FastGenByArgs("args length must be greater than 4")
+			}
+			role, err := url.QueryUnescape(args[0])
+			if err != nil {
+				return errs.ErrQueryUnescape.Wrap(err)
+			}
+			jobRole := NewRole(role)
+			if jobRole == unknown {
+				return errs.ErrQueryUnescape.FastGenByArgs("role")
+			}
+			engine, err := url.QueryUnescape(args[1])
+			if err != nil {
+				return errs.ErrQueryUnescape.Wrap(err)
+			}
+			timeout, err := url.QueryUnescape(args[2])
+			if err != nil {
+				return errs.ErrQueryUnescape.Wrap(err)
+			}
+			duration, err := time.ParseDuration(timeout)
+			if err != nil {
+				return errs.ErrURLParse.Wrap(err)
+			}
+			alias, err := url.QueryUnescape(args[3])
+			if err != nil {
+				return errs.ErrURLParse.Wrap(err)
+			}
+			ranges, err := getKeyRanges(args[4:])
+			if err != nil {
+				return err
+			}
+
+			id := uint64(0)
+			if len(conf.jobs) > 0 {
+				id = conf.jobs[len(conf.jobs)-1].JobID + 1
+			}
+
+			job := &balanceRangeSchedulerJob{
+				Role:    jobRole,
+				Engine:  engine,
+				Timeout: duration,
+				Alias:   alias,
+				Ranges:  ranges,
+				Status:  pending,
+				JobID:   id,
+			}
+			conf.jobs = append(conf.jobs, job)
+			return nil
+		}
+	})
+
+	RegisterScheduler(types.BalanceRangeScheduler, func(opController *operator.Controller,
+		storage endpoint.ConfigStorage, decoder ConfigDecoder, _ ...func(string) error) (Scheduler, error) {
+		conf := &balanceRangeSchedulerConfig{
+			schedulerConfig: newBaseDefaultSchedulerConfig(),
+		}
+		if err := decoder(conf); err != nil {
+			return nil, err
+		}
+		sche := newBalanceRangeScheduler(opController, conf)
+		conf.init(sche.GetName(), storage, conf)
+		return sche, nil
+	})
 }