ddl: fix waiting for wrong schema version if TiDB server restart (#39985

)

close #39981

ddl/ddl_worker.go

@@ -536,16 +536,20 @@ func cleanMDLInfo(pool *sessionPool, jobID int64, ec *clientv3.Client) {
 }
 
 // checkMDLInfo checks if metadata lock info exists. It means the schema is locked by some TiDBs if exists.
-func checkMDLInfo(jobID int64, pool *sessionPool) (bool, error) {
-	sql := fmt.Sprintf("select * from mysql.tidb_mdl_info where job_id = %d", jobID)
+func checkMDLInfo(jobID int64, pool *sessionPool) (bool, int64, error) {
+	sql := fmt.Sprintf("select version from mysql.tidb_mdl_info where job_id = %d", jobID)
 	sctx, _ := pool.get()
 	defer pool.put(sctx)
 	sess := newSession(sctx)
 	rows, err := sess.execute(context.Background(), sql, "check-mdl-info")
 	if err != nil {
-		return false, err
+		return false, 0, err
 	}
-	return len(rows) > 0, nil
+	if len(rows) == 0 {
+		return false, 0, nil
+	}
+	ver := rows[0].GetInt64(0)
+	return true, ver, nil
 }
 
 func needUpdateRawArgs(job *model.Job, meetErr bool) bool {
@@ -1377,6 +1381,32 @@ func waitSchemaChanged(ctx context.Context, d *ddlCtx, waitTime time.Duration, l
 		zap.String("job", job.String()))
 }
 
+// waitSchemaSyncedForMDL likes waitSchemaSynced, but it waits for getting the metadata lock of the latest version of this DDL.
+func waitSchemaSyncedForMDL(d *ddlCtx, job *model.Job, latestSchemaVersion int64) error {
+	failpoint.Inject("checkDownBeforeUpdateGlobalVersion", func(val failpoint.Value) {
+		if val.(bool) {
+			if mockDDLErrOnce > 0 && mockDDLErrOnce != latestSchemaVersion {
+				panic("check down before update global version failed")
+			} else {
+				mockDDLErrOnce = -1
+			}
+		}
+	})
+
+	timeStart := time.Now()
+	// OwnerCheckAllVersions returns only when all TiDB schemas are synced(exclude the isolated TiDB).
+	err := d.schemaSyncer.OwnerCheckAllVersions(context.Background(), job.ID, latestSchemaVersion)
+	if err != nil {
+		logutil.Logger(d.ctx).Info("[ddl] wait latest schema version encounter error", zap.Int64("ver", latestSchemaVersion), zap.Error(err))
+		return err
+	}
+	logutil.Logger(d.ctx).Info("[ddl] wait latest schema version changed(get the metadata lock if tidb_enable_metadata_lock is true)",
+		zap.Int64("ver", latestSchemaVersion),
+		zap.Duration("take time", time.Since(timeStart)),
+		zap.String("job", job.String()))
+	return nil
+}
+
 // waitSchemaSynced handles the following situation:
 // If the job enters a new state, and the worker crashs when it's in the process of waiting for 2 * lease time,
 // Then the worker restarts quickly, we may run the job immediately again,

ddl/job_table.go

@@ -237,7 +237,7 @@ func (d *ddl) delivery2worker(wk *worker, pool *workerPool, job *model.Job) {
 		// check if this ddl job is synced to all servers.
 		if !d.isSynced(job) || d.once.Load() {
 			if variable.EnableMDL.Load() {
-				exist, err := checkMDLInfo(job.ID, d.sessPool)
+				exist, version, err := checkMDLInfo(job.ID, d.sessPool)
 				if err != nil {
 					logutil.BgLogger().Warn("[ddl] check MDL info failed", zap.Error(err), zap.String("job", job.String()))
 					// Release the worker resource.
@@ -246,10 +246,8 @@ func (d *ddl) delivery2worker(wk *worker, pool *workerPool, job *model.Job) {
 				} else if exist {
 					// Release the worker resource.
 					pool.put(wk)
-					err = waitSchemaSynced(d.ddlCtx, job, 2*d.lease)
+					err = waitSchemaSyncedForMDL(d.ddlCtx, job, version)
 					if err != nil {
-						logutil.BgLogger().Warn("[ddl] wait ddl job sync failed", zap.Error(err), zap.String("job", job.String()))
-						time.Sleep(time.Second)
 						return
 					}
 					d.once.Store(false)