*: add engine filter to exclude special stores

server/schedule/filter/filters.go

@@ -543,12 +543,51 @@ func (f *ruleFitFilter) Target(opt opt.Options, store *core.StoreInfo) bool {
 	return placement.CompareRegionFit(f.oldFit, newFit) <= 0
 }
 
+type engineFilter struct {
+	scope      string
+	constraint placement.LabelConstraint
+}
+
+// NewEngineFilter creates a filter that filters out default engine stores.
+// By default, all stores that are not marked with a special engine will be filtered out.
+// Specify the special engine label if you want to include the special stores.
+func NewEngineFilter(scope string, allowEngines ...string) Filter {
+	var values []string
+	for _, v := range allSpeicalEngines {
+		if slice.NoneOf(allowEngines, func(i int) bool { return allowEngines[i] == v }) {
+			values = append(values, v)
+		}
+	}
+	return &engineFilter{
+		scope:      scope,
+		constraint: placement.LabelConstraint{Key: "engine", Op: "notIn", Values: values},
+	}
+}
+
+func (f *engineFilter) Scope() string {
+	return f.scope
+}
+
+func (f *engineFilter) Type() string {
+	return "engine-filter"
+}
+
+func (f *engineFilter) Source(opt opt.Options, store *core.StoreInfo) bool {
+	return f.constraint.MatchStore(store)
+}
+
+func (f *engineFilter) Target(opt opt.Options, store *core.StoreInfo) bool {
+	return f.constraint.MatchStore(store)
+}
+
 type specialUseFilter struct {
 	scope      string
 	constraint placement.LabelConstraint
 }
 
-// NewSpecialUseFilter creates a filter that filters stores for special use.
+// NewSpecialUseFilter creates a filter that filters out normal stores.
+// By default, all stores that are not marked with a special use will be filtered out.
+// Specify the special use label if you want to include the special stores.
 func NewSpecialUseFilter(scope string, allowUses ...string) Filter {
 	var values []string
 	for _, v := range allSpecialUses {
@@ -558,7 +597,7 @@ func NewSpecialUseFilter(scope string, allowUses ...string) Filter {
 	}
 	return &specialUseFilter{
 		scope:      scope,
-		constraint: placement.LabelConstraint{Key: specialUseKey, Op: "in", Values: values},
+		constraint: placement.LabelConstraint{Key: SpecialUseKey, Op: "in", Values: values},
 	}
 }
 
@@ -582,11 +621,18 @@ func (f *specialUseFilter) Target(opt opt.Options, store *core.StoreInfo) bool {
 }
 
 const (
-	specialUseKey = "specialUse"
+	// SpecialUseKey is the label used to indicate special use storage.
+	SpecialUseKey = "specialUse"
 	// SpecialUseHotRegion is the hot region value of special use label
 	SpecialUseHotRegion = "hotRegion"
 	// SpecialUseReserved is the reserved value of special use label
 	SpecialUseReserved = "reserved"
+
+	// EngineKey is the label key used to indicate engine.
+	EngineKey = "engine"
+	// EngineTiFlash is the tiflash value of the engine label.
+	EngineTiFlash = "tiflash"
 )
 
 var allSpecialUses = []string{SpecialUseHotRegion, SpecialUseReserved}
+var allSpeicalEngines = []string{EngineTiFlash}

server/schedule/region_scatterer.go

@@ -82,6 +82,7 @@ func NewRegionScatterer(cluster opt.Cluster) *RegionScatterer {
 		cluster: cluster,
 		filters: []filter.Filter{
 			filter.StoreStateFilter{ActionScope: regionScatterName},
+			filter.NewEngineFilter(regionScatterName),
 		},
 		selected: newSelectedStores(),
 	}

server/schedulers/scheduler_test.go

@@ -189,11 +189,13 @@ var _ = Suite(&testScatterRegionSuite{})
 type testScatterRegionSuite struct{}
 
 func (s *testScatterRegionSuite) TestSixStores(c *C) {
-	s.scatter(c, 6, 4)
+	s.scatter(c, 6, 4, false)
+	s.scatter(c, 6, 4, true)
 }
 
 func (s *testScatterRegionSuite) TestFiveStores(c *C) {
-	s.scatter(c, 5, 5)
+	s.scatter(c, 5, 5, false)
+	s.scatter(c, 5, 5, true)
 }
 
 func (s *testScatterRegionSuite) checkOperator(op *operator.Operator, c *C) {
@@ -209,14 +211,16 @@ func (s *testScatterRegionSuite) checkOperator(op *operator.Operator, c *C) {
 	}
 }
 
-func (s *testScatterRegionSuite) scatter(c *C, numStores, numRegions uint64) {
+func (s *testScatterRegionSuite) scatter(c *C, numStores, numRegions uint64, useRules bool) {
 	opt := mockoption.NewScheduleOptions()
 	tc := mockcluster.NewCluster(opt)
 
 	// Add stores 1~6.
 	for i := uint64(1); i <= numStores; i++ {
 		tc.AddRegionStore(i, 0)
 	}
+	tc.AddLabelsStore(numStores+1, 0, map[string]string{"engine": "tiflash"})
+	tc.EnablePlacementRules = useRules
 
 	// Add regions 1~4.
 	seq := newSequencer(3)

server/util.go

@@ -183,6 +183,8 @@ func checkBootstrapRequest(clusterID uint64, req *pdpb.BootstrapRequest) error {
 	return nil
 }
 
+// isTiFlashStore used to judge flash store.
+// FIXME: remove the hack way
 func isTiFlashStore(store *metapb.Store) bool {
 	for _, l := range store.GetLabels() {
 		if l.GetKey() == "engine" && l.GetValue() == "tiflash" {