ddl, owner: refresh ddl sequence cache after becoming the owner

ddl/ddl.go

@@ -476,6 +476,14 @@ func (d *ddl) Start(ctxPool *pools.ResourcePool) error {
 	// If RunWorker is true, we need campaign owner and do DDL job.
 	// Otherwise, we needn't do that.
 	if RunWorker {
+		d.ownerManager.SetBeOwnerHook(func() {
+			var err error
+			d.ddlSeqNumMu.seqNum, err = d.GetNextDDLSeqNum()
+			if err != nil {
+				logutil.BgLogger().Error("error when getting the ddl history count", zap.Error(err))
+			}
+		})
+
 		err := d.ownerManager.CampaignOwner()
 		if err != nil {
 			return errors.Trace(err)
@@ -497,11 +505,6 @@ func (d *ddl) Start(ctxPool *pools.ResourcePool) error {
 			asyncNotify(worker.ddlJobCh)
 		}
 
-		d.ddlSeqNumMu.seqNum, err = d.GetNextDDLSeqNum()
-		if err != nil {
-			return err
-		}
-
 		go d.schemaSyncer.StartCleanWork()
 		if config.TableLockEnabled() {
 			d.wg.Add(1)

owner/manager.go

@@ -54,6 +54,9 @@ type Manager interface {
 	Cancel()
 	// RequireOwner requires the ownerManager is owner.
 	RequireOwner(ctx context.Context) error
+
+	// SetBeOwnerHook sets a hook. The hook is called before becoming an owner.
+	SetBeOwnerHook(hook func())
 }
 
 const (
@@ -68,16 +71,17 @@ type DDLOwnerChecker interface {
 
 // ownerManager represents the structure which is used for electing owner.
 type ownerManager struct {
-	id        string // id is the ID of the manager.
-	key       string
-	ctx       context.Context
-	prompt    string
-	logPrefix string
-	logCtx    context.Context
-	etcdCli   *clientv3.Client
-	cancel    context.CancelFunc
-	elec      unsafe.Pointer
-	wg        sync.WaitGroup
+	id          string // id is the ID of the manager.
+	key         string
+	ctx         context.Context
+	prompt      string
+	logPrefix   string
+	logCtx      context.Context
+	etcdCli     *clientv3.Client
+	cancel      context.CancelFunc
+	elec        unsafe.Pointer
+	wg          sync.WaitGroup
+	beOwnerHook func()
 }
 
 // NewOwnerManager creates a new Manager.
@@ -117,6 +121,10 @@ func (m *ownerManager) RequireOwner(ctx context.Context) error {
 	return nil
 }
 
+func (m *ownerManager) SetBeOwnerHook(hook func()) {
+	m.beOwnerHook = hook
+}
+
 // ManagerSessionTTL is the etcd session's TTL in seconds. It's exported for testing.
 var ManagerSessionTTL = 60
 
@@ -166,6 +174,9 @@ func (m *ownerManager) ResignOwner(ctx context.Context) error {
 }
 
 func (m *ownerManager) toBeOwner(elec *concurrency.Election) {
+	if m.beOwnerHook != nil {
+		m.beOwnerHook()
+	}
 	atomic.StorePointer(&m.elec, unsafe.Pointer(elec))
 }
 

owner/mock.go

@@ -27,9 +27,10 @@ var _ Manager = &mockManager{}
 // It's used for local store and testing.
 // So this worker will always be the owner.
 type mockManager struct {
-	owner  int32
-	id     string // id is the ID of manager.
-	cancel context.CancelFunc
+	owner       int32
+	id          string // id is the ID of manager.
+	cancel      context.CancelFunc
+	beOwnerHook func()
 }
 
 // NewMockManager creates a new mock Manager.
@@ -52,6 +53,9 @@ func (m *mockManager) IsOwner() bool {
 }
 
 func (m *mockManager) toBeOwner() {
+	if m.beOwnerHook != nil {
+		m.beOwnerHook()
+	}
 	atomic.StoreInt32(&m.owner, 1)
 }
 
@@ -91,3 +95,7 @@ func (m *mockManager) ResignOwner(ctx context.Context) error {
 func (m *mockManager) RequireOwner(context.Context) error {
 	return nil
 }
+
+func (m *mockManager) SetBeOwnerHook(hook func()) {
+	m.beOwnerHook = hook
+}