[WIP] Add optimistic sharding mode

dm/ctl/ctl.go

@@ -68,6 +68,7 @@ func NewRootCmd() *cobra.Command {
 		master.NewShowDDLLocksCmd(),
 		master.NewUnlockDDLLockCmd(),
 		master.NewBreakDDLLockCmd(),
+		master.NewSetDDLLockModeCmd(),
 		master.NewSwitchRelayMasterCmd(),
 		master.NewPauseRelayCmd(),
 		master.NewResumeRelayCmd(),

dm/ctl/master/set_ddl_lock_mode.go

@@ -0,0 +1,70 @@
+// Copyright 2020 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package master
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/pingcap/dm/dm/ctl/common"
+	"github.com/pingcap/dm/dm/pb"
+	"github.com/pingcap/dm/pkg/shardddl/pessimism"
+
+	"github.com/pingcap/errors"
+	"github.com/spf13/cobra"
+)
+
+// NewSetDDLLockModeCmd creates a SetDDLLockMode command
+func NewSetDDLLockModeCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "set-ddl-lock-mode <mode>",
+		Short: "switch between optimistic and pessimistic modes for new DDL locks",
+		Run:   setDDLLockModeFunc,
+	}
+	return cmd
+}
+
+// breakDDLLockFunc does break DDL lock
+func setDDLLockModeFunc(cmd *cobra.Command, _ []string) {
+	if len(cmd.Flags().Args()) != 1 {
+		cmd.SetOut(os.Stdout)
+		cmd.Usage()
+		return
+	}
+
+	var lockMode pessimism.LockMode
+	switch lockModeStr := cmd.Flags().Arg(0); lockModeStr {
+	case "optimistic":
+		lockMode = pessimism.LockModeOptimistic
+	case "pessimistic":
+		lockMode = pessimism.LockModePessimistic
+	default:
+		fmt.Println("unknown lock mode", lockModeStr)
+		return
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	cli := common.MasterClient()
+	resp, err := cli.SetDDLLockMode(ctx, &pb.SetDDLLockModeRequest{
+		LockMode: uint32(lockMode),
+	})
+	if err != nil {
+		common.PrintLines("cannot change lock mode:\n%s", errors.ErrorStack(err))
+		return
+	}
+
+	common.PrettyPrintResponse(resp)
+}