it can transfer leader between the different rule

Signed-off-by: bufferflies <1045931706@qq.com>

pkg/schedule/filter/filters.go

@@ -639,7 +639,7 @@ func (f *ruleFitFilter) Source(_ config.Config, _ *core.StoreInfo) *plan.Status
 // the replaced store can match the source rule.
 // RegionA:[1,2,3], move peer1 --> peer2 will not allow, because it's count not match the rule.
 // but transfer role peer1 --> peer2, it will support.
-func (f *ruleFitFilter) Target(options config.Config, store *core.StoreInfo) *plan.Status {
+func (f *ruleFitFilter) Target(_ config.Config, store *core.StoreInfo) *plan.Status {
 	if f.oldFit.Replace(f.srcStore, store) {
 		return statusOK
 	}

pkg/schedule/placement/fit.go

@@ -39,15 +39,27 @@ type RegionFit struct {
 func (f *RegionFit) Replace(srcStoreID uint64, dstStore *core.StoreInfo) bool {
 	fit := f.getRuleFitByStoreID(srcStoreID)
 	// check the target store is fit all constraints.
-	if fit == nil || !MatchLabelConstraints(dstStore, fit.Rule.LabelConstraints) {
+	if fit == nil {
 		return false
 	}
-
 	// the members of the rule are same, it shouldn't check the score.
+	// it is used to transfer role like transfer leader.
 	if fit.contain(dstStore.GetID()) {
 		return true
 	}
 
+	// it should be allowed to exchange role if both the source and target's rule role is same.
+	// e.g. transfer leader from store 1 to store 2, and store-1 and store-2 are both voter.
+	targetFit := f.getRuleFitByStoreID(dstStore.GetID())
+	if targetFit != nil && targetFit.Rule.Role == fit.Rule.Role {
+		return true
+	}
+
+	// the target store should be fit all constraints.
+	if !MatchLabelConstraints(dstStore, fit.Rule.LabelConstraints) {
+		return false
+	}
+
 	score := isolationStoreScore(srcStoreID, dstStore, fit.stores, fit.Rule.LocationLabels)
 	// restore the source store.
 	return fit.IsolationScore <= score

pkg/schedule/placement/fit_test.go

@@ -140,6 +140,10 @@ func TestReplace(t *testing.T) {
 		{"1111_leader,1121,1131", []string{"1/leader/host=host1+host2/host", "3/voter//host"}, 1111, 1121, true},
 		// replace failed when the leader is not match the leader constraint.
 		{"1111_leader,1121,1131", []string{"1/leader/host=host1+host2/host", "2/voter//host"}, 1111, 1131, false},
+
+		// transfer leader with different rule
+		{"1111_leader,1121,1131", []string{"1/voter/host=host1/host", "1/voter/host=host2/host", "1/voter/host=host3/host"}, 1111, 1121, true},
+		{"1111_leader,1121,1131", []string{"1/leader/host=host1/host", "1/voter/host=host2/host", "1/voter/host=host3/host"}, 1111, 1121, false},
 	}
 	for _, tc := range testCases {
 		region := makeRegion(tc.region)