ddl: simply refactor the code called "needCheckClusterState" (#45660)

ref #39751

ddl/job_table.go

@@ -266,7 +266,7 @@ func (d *ddl) startDispatchLoop() {
  notifyDDLJobByEtcdCh = d.etcdCli.Watch(d.ctx, addingDDLJobConcurrent)
  }
  ticker := time.NewTicker(dispatchLoopWaitingDuration)
- if err := d.doCheckClusterState(false); err != nil {
+ if err := d.checkAndUpdateClusterState(true); err != nil {
  logutil.BgLogger().Fatal("dispatch loop get cluster state failed, it should not happen, please try restart TiDB", zap.Error(err))
  }
  defer ticker.Stop()
@@ -294,7 +294,7 @@ func (d *ddl) startDispatchLoop() {
  case <-d.ctx.Done():
  return
  }
- if err := d.needCheckClusterState(isOnce); err != nil {
+ if err := d.checkAndUpdateClusterState(isOnce); err != nil {
  continue
  }
  isOnce = false
@@ -303,23 +303,17 @@ func (d *ddl) startDispatchLoop() {
  }
 }
 
-func (d *ddl) needCheckClusterState(mustCheck bool) error {
+func (d *ddl) checkAndUpdateClusterState(needUpdate bool) error {
  select {
  case _, ok := <-d.stateSyncer.WatchChan():
- return d.doCheckClusterState(!ok)
+ if !ok {
+ d.stateSyncer.Rewatch(d.ctx)
+ }
  default:
- if mustCheck {
- return d.doCheckClusterState(false)
+ if !needUpdate {
+ return nil
  }
  }
- return nil
-}
-
-func (d *ddl) doCheckClusterState(needRewatch bool) error {
- if needRewatch {
- d.stateSyncer.Rewatch(d.ctx)
- return nil
- }
 
  oldState := d.stateSyncer.IsUpgradingState()
  stateInfo, err := d.stateSyncer.GetGlobalState(d.ctx)