address comment

Signed-off-by: husharp <jinhao.hu@pingcap.com>

pkg/mcs/discovery/discover.go

@@ -96,14 +96,14 @@ func TransferPrimary(client *clientv3.Client, serviceName, oldPrimary, newPrimar
 	}
 
 	var primaryIDs []string
-	var secondaryValues []string
+	var memberValues []string
 	for _, member := range entries {
 		if (newPrimary == "" && member.ServiceAddr != oldPrimary) || (newPrimary != "" && member.Name == newPrimary) {
 			primaryIDs = append(primaryIDs, member.ServiceAddr)
 			if string(member.MemberValue) == "" {
 				return errors.New(fmt.Sprintf("member %s value is empty", member.Name))
 			}
-			secondaryValues = append(secondaryValues, string(member.MemberValue))
+			memberValues = append(memberValues, string(member.MemberValue))
 		}
 	}
 	if len(primaryIDs) == 0 {
@@ -128,7 +128,7 @@ func TransferPrimary(client *clientv3.Client, serviceName, oldPrimary, newPrimar
 	}
 
 	// remove possible residual value.
-	utils.RemoveExpectedPrimary(client, primaryKey)
+	utils.ClearPrimaryExpectationFlag(client, primaryKey)
 
 	// grant the primary lease to the new primary.
 	grantResp, err := client.Grant(client.Ctx(), utils.DefaultLeaderLease)
@@ -137,7 +137,7 @@ func TransferPrimary(client *clientv3.Client, serviceName, oldPrimary, newPrimar
 	}
 	// update primary key to notify old primary server.
 	putResp, err := kv.NewSlowLogTxn(client).
-		Then(clientv3.OpPut(primaryKey, secondaryValues[nextPrimaryID], clientv3.WithLease(grantResp.ID))).
+		Then(clientv3.OpPut(primaryKey, memberValues[nextPrimaryID], clientv3.WithLease(grantResp.ID))).
 		Commit()
 	if err != nil || !putResp.Succeeded {
 		return errors.Errorf("failed to write primary flag for %s, err: %v", serviceName, err)

pkg/mcs/scheduling/server/server.go

@@ -249,7 +249,7 @@ func (s *Server) primaryElectionLoop() {
 		}
 
 		// To make sure the expected primary(if existed) and new primary are on the same server.
-		expectedPrimary := utils.GetExpectedPrimary(s.GetClient(), s.participant.GetLeaderPath())
+		expectedPrimary := utils.AttachExpectedPrimaryFlag(s.GetClient(), s.participant.GetLeaderPath())
 		// skip campaign the primary if the expected primary is not empty and not equal to the current memberValue.
 		// expected primary ONLY SET BY `/ms/primary/transfer` API.
 		if expectedPrimary != "" && expectedPrimary != s.participant.MemberValue() {
@@ -358,7 +358,7 @@ func (s *Server) primaryWatch(ctx context.Context, exitPrimary chan struct{}) {
 	}
 	if curPrimary != nil && resp.Kvs[0].Value != nil && string(curPrimary) != string(resp.Kvs[0].Value) {
 		// 1. modify the expected primary flag to the new primary.
-		utils.SetExpectedPrimary(s.participant.Client(), s.participant.GetLeaderPath())
+		utils.MarkExpectedPrimaryFlag(s.participant.Client(), s.participant.GetLeaderPath())
 		// 2. modify memory status.
 		s.participant.UnsetLeader()
 		defer log.Info("scheduling primary exit the primary watch loop")

pkg/mcs/utils/util.go

@@ -52,13 +52,13 @@ const (
 	ClusterIDPath = "/pd/cluster_id"
 	// retryInterval is the interval to retry.
 	retryInterval = time.Second
-	// ExpectedPrimary is the path to store the expected primary , ONLY Triggered BY `/ms/primary/transfer` API.
+	// ExpectedPrimaryFlag is the flag to indicate the expected primary, ONLY marked BY `/ms/primary/transfer` API.
 	// This flag likes a fence to avoid exited 2 primaries in the cluster simultaneously.
 	// 1. Since follower will campaign a new primary when it found the `leader_key` is deleted.
 	// **We can ensure `expected_primary` is set before deleting the `leader_key`.**
-	// 2. Old primary will set `expected_primary` firstly,
+	// 2. Old primary will mark `expected_primary` firstly,
 	// then delete the `leader_key` which will trigger the follower to campaign a new primary.
-	ExpectedPrimary = "expected_primary"
+	ExpectedPrimaryFlag = "expected_primary"
 )
 
 // InitClusterID initializes the cluster ID.
@@ -78,35 +78,35 @@ func InitClusterID(ctx context.Context, client *clientv3.Client) (id uint64, err
 	return 0, errors.Errorf("failed to init cluster ID after retrying %d times", maxRetryTimes)
 }
 
-// GetExpectedPrimary indicates API has changed the primary.
-func GetExpectedPrimary(client *clientv3.Client, leaderPath string) string {
-	primary, err := etcdutil.GetValue(client, strings.Join([]string{leaderPath, ExpectedPrimary}, "/"))
+// AttachExpectedPrimaryFlag attaches the expected primary flag.
+func AttachExpectedPrimaryFlag(client *clientv3.Client, leaderPath string) string {
+	primary, err := etcdutil.GetValue(client, strings.Join([]string{leaderPath, ExpectedPrimaryFlag}, "/"))
 	if err != nil {
-		log.Error("get expected primary key error", errs.ZapError(err))
+		log.Error("get expected primary flag error", errs.ZapError(err))
 		return ""
 	}
 
 	return string(primary)
 }
 
-// RemoveExpectedPrimary removes the expected primary key.
+// ClearPrimaryExpectationFlag clears the expected primary flag.
 // - removed when campaign new primary successfully.
 // - removed when appoint new primary by API.
-func RemoveExpectedPrimary(client *clientv3.Client, leaderPath string) {
-	log.Info("remove expected primary key", zap.String("leader-path", leaderPath))
+func ClearPrimaryExpectationFlag(client *clientv3.Client, leaderPath string) {
+	log.Info("remove expected primary flag", zap.String("primary-path", leaderPath))
 	// remove expected leader key
 	resp, err := kv.NewSlowLogTxn(client).
-		Then(clientv3.OpDelete(strings.Join([]string{leaderPath, ExpectedPrimary}, "/"))).
+		Then(clientv3.OpDelete(strings.Join([]string{leaderPath, ExpectedPrimaryFlag}, "/"))).
 		Commit()
 	if err != nil || !resp.Succeeded {
 		log.Error("change expected primary error", errs.ZapError(err))
 		return
 	}
 }
 
-// SetExpectedPrimary sets the expected primary key when the current primary has exited.
-func SetExpectedPrimary(client *clientv3.Client, leaderPath string) {
-	log.Info("set expected primary key", zap.String("leader-path", leaderPath))
+// MarkExpectedPrimaryFlag marks the expected primary flag when the current primary has exited.
+func MarkExpectedPrimaryFlag(client *clientv3.Client, leaderPath string) {
+	log.Info("set expected primary flag", zap.String("leader-path", leaderPath))
 	leaderRaw, err := etcdutil.GetValue(client, leaderPath)
 	if err != nil {
 		log.Error("get primary key error", zap.Error(err))
@@ -120,7 +120,7 @@ func SetExpectedPrimary(client *clientv3.Client, leaderPath string) {
 	// write a flag to indicate the current primary has exited
 	resp, err := kv.NewSlowLogTxn(client).
 		Then(
-			clientv3.OpPut(strings.Join([]string{leaderPath, ExpectedPrimary}, "/"), string(leaderRaw), clientv3.WithLease(grantResp.ID)),
+			clientv3.OpPut(strings.Join([]string{leaderPath, ExpectedPrimaryFlag}, "/"), string(leaderRaw), clientv3.WithLease(grantResp.ID)),
 			// indicate the current primary has exited
 			clientv3.OpDelete(leaderPath)).
 		Commit()

pkg/member/member.go

@@ -158,7 +158,7 @@ func (m *EmbeddedEtcdMember) UnsetLeader() {
 // EnableLeader sets the member itself to a PD leader.
 func (m *EmbeddedEtcdMember) EnableLeader() {
 	m.setLeader(m.member)
-	utils.RemoveExpectedPrimary(m.client, m.GetLeaderPath())
+	utils.ClearPrimaryExpectationFlag(m.client, m.GetLeaderPath())
 }
 
 // GetLeaderPath returns the path of the PD leader.

pkg/member/participant.go

@@ -164,7 +164,7 @@ func (m *Participant) UnsetLeader() {
 // EnableLeader declares the member itself to be the leader.
 func (m *Participant) EnableLeader() {
 	m.setLeader(m.member)
-	utils.RemoveExpectedPrimary(m.client, m.GetLeaderPath())
+	utils.ClearPrimaryExpectationFlag(m.client, m.GetLeaderPath())
 }
 
 // GetLeaderPath returns the path of the leader.

pkg/tso/global_allocator.go

@@ -562,7 +562,7 @@ func (gta *GlobalTSOAllocator) primaryElectionLoop() {
 		}
 
 		// To make sure the expected primary(if existed) and new primary are on the same server.
-		expectedPrimary := mcsutils.GetExpectedPrimary(gta.member.Client(), gta.member.GetLeaderPath())
+		expectedPrimary := mcsutils.AttachExpectedPrimaryFlag(gta.member.Client(), gta.member.GetLeaderPath())
 		// skip campaign the primary if the expected primary is not empty and not equal to the current memberValue.
 		// expected primary ONLY SET BY `/ms/primary/transfer` API.
 		if expectedPrimary != "" && expectedPrimary != gta.member.MemberValue() {
@@ -703,7 +703,7 @@ func (gta *GlobalTSOAllocator) primaryWatch(ctx context.Context, exitPrimary cha
 	}
 	if curPrimary != nil && resp.Kvs[0].Value != nil && string(curPrimary) != string(resp.Kvs[0].Value) {
 		// 1. modify the expected primary flag to the new primary.
-		mcsutils.SetExpectedPrimary(gta.member.Client(), gta.member.GetLeaderPath())
+		mcsutils.MarkExpectedPrimaryFlag(gta.member.Client(), gta.member.GetLeaderPath())
 		// 2. modify memory status.
 		gta.member.UnsetLeader()
 		defer log.Info("tso primary exit the primary watch loop")