Golang topo.UpdateKeyspace函数代码示例

func (wr *Wrangler) setKeyspaceShardingInfo(keyspace, shardingColumnName string, shardingColumnType key.KeyspaceIdType, force bool) error {
	ki, err := wr.ts.GetKeyspace(keyspace)
	if err != nil {
		return err
	}

	if ki.ShardingColumnName != "" && ki.ShardingColumnName != shardingColumnName {
		if force {
			log.Warningf("Forcing keyspace ShardingColumnName change from %v to %v", ki.ShardingColumnName, shardingColumnName)
		} else {
			return fmt.Errorf("Cannot change ShardingColumnName from %v to %v (use -force to override)", ki.ShardingColumnName, shardingColumnName)
		}
	}

	if ki.ShardingColumnType != key.KIT_UNSET && ki.ShardingColumnType != shardingColumnType {
		if force {
			log.Warningf("Forcing keyspace ShardingColumnType change from %v to %v", ki.ShardingColumnType, shardingColumnType)
		} else {
			return fmt.Errorf("Cannot change ShardingColumnType from %v to %v (use -force to override)", ki.ShardingColumnType, shardingColumnType)
		}
	}

	ki.ShardingColumnName = shardingColumnName
	ki.ShardingColumnType = shardingColumnType
	return topo.UpdateKeyspace(wr.ts, ki)
}

func (wr *Wrangler) setKeyspaceShardingInfo(ctx context.Context, keyspace, shardingColumnName string, shardingColumnType pb.KeyspaceIdType, splitShardCount int32, force bool) error {
	ki, err := wr.ts.GetKeyspace(ctx, keyspace)
	if err != nil {
		return err
	}

	if ki.ShardingColumnName != "" && ki.ShardingColumnName != shardingColumnName {
		if force {
			wr.Logger().Warningf("Forcing keyspace ShardingColumnName change from %v to %v", ki.ShardingColumnName, shardingColumnName)
		} else {
			return fmt.Errorf("Cannot change ShardingColumnName from %v to %v (use -force to override)", ki.ShardingColumnName, shardingColumnName)
		}
	}

	if ki.ShardingColumnType != pb.KeyspaceIdType_UNSET && ki.ShardingColumnType != shardingColumnType {
		if force {
			wr.Logger().Warningf("Forcing keyspace ShardingColumnType change from %v to %v", ki.ShardingColumnType, shardingColumnType)
		} else {
			return fmt.Errorf("Cannot change ShardingColumnType from %v to %v (use -force to override)", ki.ShardingColumnType, shardingColumnType)
		}
	}

	ki.ShardingColumnName = shardingColumnName
	ki.ShardingColumnType = shardingColumnType
	ki.SplitShardCount = splitShardCount
	return topo.UpdateKeyspace(ctx, wr.ts, ki)
}

// replicaMigrateServedFrom handles the slave (replica, rdonly) migration.
func (wr *Wrangler) replicaMigrateServedFrom(ctx context.Context, ki *topo.KeyspaceInfo, sourceShard *topo.ShardInfo, destinationShard *topo.ShardInfo, servedType pb.TabletType, cells []string, reverse bool, tables []string, ev *events.MigrateServedFrom) error {
	// Save the destination keyspace (its ServedFrom has been changed)
	event.DispatchUpdate(ev, "updating keyspace")
	if err := topo.UpdateKeyspace(ctx, wr.ts, ki); err != nil {
		return err
	}

	// Save the source shard (its blacklisted tables field has changed)
	event.DispatchUpdate(ev, "updating source shard")
	if err := sourceShard.UpdateSourceBlacklistedTables(servedType, cells, reverse, tables); err != nil {
		return fmt.Errorf("UpdateSourceBlacklistedTables(%v/%v) failed: %v", sourceShard.Keyspace(), sourceShard.ShardName(), err)
	}
	if err := topo.UpdateShard(ctx, wr.ts, sourceShard); err != nil {
		return fmt.Errorf("UpdateShard(%v/%v) failed: %v", sourceShard.Keyspace(), sourceShard.ShardName(), err)
	}

	// Now refresh the source servers so they reload their
	// blacklisted table list
	event.DispatchUpdate(ev, "refreshing sources tablets state so they update their blacklisted tables")
	if err := wr.RefreshTablesByShard(ctx, sourceShard, servedType, cells); err != nil {
		return err
	}

	return nil
}

// replicaMigrateServedFrom handles the slave (replica, rdonly) migration.
func (wr *Wrangler) replicaMigrateServedFrom(ki *topo.KeyspaceInfo, sourceShard *topo.ShardInfo, destinationShard *topo.ShardInfo, servedType topo.TabletType, reverse bool, tables []string, ev *events.MigrateServedFrom) error {
	// Save the destination keyspace (its ServedFrom has been changed)
	event.DispatchUpdate(ev, "updating keyspace")
	if err := topo.UpdateKeyspace(wr.ts, ki); err != nil {
		return err
	}

	// Save the source shard (its blacklisted tables field has changed)
	event.DispatchUpdate(ev, "updating source shard")
	if sourceShard.BlacklistedTablesMap == nil {
		sourceShard.BlacklistedTablesMap = make(map[topo.TabletType][]string)
	}
	if reverse {
		delete(sourceShard.BlacklistedTablesMap, servedType)
	} else {
		sourceShard.BlacklistedTablesMap[servedType] = tables
	}
	if err := topo.UpdateShard(wr.ts, sourceShard); err != nil {
		return err
	}

	// Now refresh the source servers so they reload their
	// blacklisted table list
	event.DispatchUpdate(ev, "refreshing sources tablets state so they update their blacklisted tables")
	if err := wr.RefreshTablesByShard(sourceShard.Keyspace(), sourceShard.ShardName(), servedType); err != nil {
		return err
	}

	return nil
}

func (wr *Wrangler) setKeyspaceServedFrom(ctx context.Context, keyspace string, servedType pb.TabletType, cells []string, sourceKeyspace string, remove bool) error {
	ki, err := wr.ts.GetKeyspace(ctx, keyspace)
	if err != nil {
		return err
	}
	if err := ki.UpdateServedFromMap(servedType, cells, sourceKeyspace, remove, nil); err != nil {
		return err
	}
	return topo.UpdateKeyspace(ctx, wr.ts, ki)
}

func (wr *Wrangler) migrateServedFrom(ki *topo.KeyspaceInfo, si *topo.ShardInfo, servedType topo.TabletType, reverse bool) (err error) {

	// re-read and update keyspace info record
	ki, err = wr.ts.GetKeyspace(ki.KeyspaceName())
	if err != nil {
		return err
	}
	if reverse {
		if _, ok := ki.ServedFrom[servedType]; ok {
			return fmt.Errorf("Destination Keyspace %s is not serving type %v", ki.KeyspaceName(), servedType)
		}
		ki.ServedFrom[servedType] = si.SourceShards[0].Keyspace
	} else {
		if _, ok := ki.ServedFrom[servedType]; !ok {
			return fmt.Errorf("Destination Keyspace %s is already serving type %v", ki.KeyspaceName(), servedType)
		}
		delete(ki.ServedFrom, servedType)
	}

	// re-read and check the destination shard
	si, err = wr.ts.GetShard(si.Keyspace(), si.ShardName())
	if err != nil {
		return err
	}
	if len(si.SourceShards) != 1 {
		return fmt.Errorf("Destination shard %v/%v is not a vertical split target", si.Keyspace(), si.ShardName())
	}
	tables := si.SourceShards[0].Tables

	// read the source shard, we'll need its master
	sourceShard, err := wr.ts.GetShard(si.SourceShards[0].Keyspace, si.SourceShards[0].Shard)
	if err != nil {
		return err
	}

	ev := &events.MigrateServedFrom{
		Keyspace:         *ki,
		SourceShard:      *sourceShard,
		DestinationShard: *si,
		ServedType:       servedType,
		Reverse:          reverse,
	}
	event.DispatchUpdate(ev, "start")
	defer func() {
		if err != nil {
			event.DispatchUpdate(ev, "failed: "+err.Error())
		}
	}()

	// For master type migration, need to:
	// - switch the source shard to read-only
	// - gather the replication point
	// - wait for filtered replication to catch up before we continue
	// - disable filtered replication after the fact
	var sourceMasterTabletInfo *topo.TabletInfo
	if servedType == topo.TYPE_MASTER {
		// set master to read-only
		event.DispatchUpdate(ev, "setting source shard master to read-only")
		actionPath, err := wr.ai.SetReadOnly(sourceShard.MasterAlias)
		if err != nil {
			return err
		}
		if err := wr.WaitForCompletion(actionPath); err != nil {
			return err
		}

		// get the position
		event.DispatchUpdate(ev, "getting master position")
		sourceMasterTabletInfo, err = wr.ts.GetTablet(sourceShard.MasterAlias)
		if err != nil {
			return err
		}
		masterPosition, err := wr.ai.MasterPosition(sourceMasterTabletInfo, wr.ActionTimeout())
		if err != nil {
			return err
		}

		// wait for it
		event.DispatchUpdate(ev, "waiting for destination master to catch up to source master")
		if err := wr.ai.WaitBlpPosition(si.MasterAlias, blproto.BlpPosition{
			Uid:      0,
			Position: masterPosition,
		}, wr.ActionTimeout()); err != nil {
			return err
		}

		// and clear the shard record
		si.SourceShards = nil
	}

	// All is good, we can save the keyspace and shard (if needed) now
	event.DispatchUpdate(ev, "updating keyspace")
	if err = topo.UpdateKeyspace(wr.ts, ki); err != nil {
		return err
	}
	event.DispatchUpdate(ev, "updating destination shard")
	if servedType == topo.TYPE_MASTER {
		if err := topo.UpdateShard(wr.ts, si); err != nil {
			return err
		}
//.........这里部分代码省略.........

// masterMigrateServedFrom handles the master migration. The ordering is
// a bit different than for rdonly / replica to guarantee a smooth transition.
//
// The order is as follows:
// - Add BlacklistedTables on the source shard map for master
// - Refresh the source master, so it stops writing on the tables
// - Get the source master position, wait until destination master reaches it
// - Clear SourceShard on the destination Shard
// - Refresh the destination master, so its stops its filtered
//   replication and starts accepting writes
func (wr *Wrangler) masterMigrateServedFrom(ctx context.Context, ki *topo.KeyspaceInfo, sourceShard *topo.ShardInfo, destinationShard *topo.ShardInfo, tables []string, ev *events.MigrateServedFrom, filteredReplicationWaitTime time.Duration) error {
	// Read the data we need
	sourceMasterTabletInfo, err := wr.ts.GetTablet(ctx, topo.ProtoToTabletAlias(sourceShard.MasterAlias))
	if err != nil {
		return err
	}
	destinationMasterTabletInfo, err := wr.ts.GetTablet(ctx, topo.ProtoToTabletAlias(destinationShard.MasterAlias))
	if err != nil {
		return err
	}

	// Update source shard (more blacklisted tables)
	event.DispatchUpdate(ev, "updating source shard")
	if err := sourceShard.UpdateSourceBlacklistedTables(pb.TabletType_MASTER, nil, false, tables); err != nil {
		return fmt.Errorf("UpdateSourceBlacklistedTables(%v/%v) failed: %v", sourceShard.Keyspace(), sourceShard.ShardName(), err)
	}
	if err := topo.UpdateShard(ctx, wr.ts, sourceShard); err != nil {
		return fmt.Errorf("UpdateShard(%v/%v) failed: %v", sourceShard.Keyspace(), sourceShard.ShardName(), err)
	}

	// Now refresh the blacklisted table list on the source master
	event.DispatchUpdate(ev, "refreshing source master so it updates its blacklisted tables")
	if err := wr.tmc.RefreshState(ctx, sourceMasterTabletInfo); err != nil {
		return err
	}

	// get the position
	event.DispatchUpdate(ev, "getting master position")
	masterPosition, err := wr.tmc.MasterPosition(ctx, sourceMasterTabletInfo)
	if err != nil {
		return err
	}

	// wait for it
	event.DispatchUpdate(ev, "waiting for destination master to catch up to source master")
	if err := wr.tmc.WaitBlpPosition(ctx, destinationMasterTabletInfo, blproto.BlpPosition{
		Uid:      0,
		Position: masterPosition,
	}, filteredReplicationWaitTime); err != nil {
		return err
	}

	// Update the destination keyspace (its ServedFrom has changed)
	event.DispatchUpdate(ev, "updating keyspace")
	if err = topo.UpdateKeyspace(ctx, wr.ts, ki); err != nil {
		return err
	}

	// Update the destination shard (no more source shard)
	event.DispatchUpdate(ev, "updating destination shard")
	destinationShard.SourceShards = nil
	if err := topo.UpdateShard(ctx, wr.ts, destinationShard); err != nil {
		return err
	}

	// Tell the new shards masters they can now be read-write.
	// Invoking a remote action will also make the tablet stop filtered
	// replication.
	event.DispatchUpdate(ev, "setting destination shard masters read-write")
	if err := wr.refreshMasters(ctx, []*topo.ShardInfo{destinationShard}); err != nil {
		return err
	}

	return nil
}

// CheckKeyspace tests the keyspace part of the API
func CheckKeyspace(ctx context.Context, t *testing.T, ts topo.Server) {
	keyspaces, err := ts.GetKeyspaces(ctx)
	if err != nil {
		t.Errorf("GetKeyspaces(empty): %v", err)
	}
	if len(keyspaces) != 0 {
		t.Errorf("len(GetKeyspaces()) != 0: %v", keyspaces)
	}

	if err := ts.CreateKeyspace(ctx, "test_keyspace", &pb.Keyspace{}); err != nil {
		t.Errorf("CreateKeyspace: %v", err)
	}
	if err := ts.CreateKeyspace(ctx, "test_keyspace", &pb.Keyspace{}); err != topo.ErrNodeExists {
		t.Errorf("CreateKeyspace(again) is not ErrNodeExists: %v", err)
	}

	// Delete and re-create.
	if err := ts.DeleteKeyspace(ctx, "test_keyspace"); err != nil {
		t.Errorf("DeleteKeyspace: %v", err)
	}
	if err := ts.CreateKeyspace(ctx, "test_keyspace", &pb.Keyspace{}); err != nil {
		t.Errorf("CreateKeyspace: %v", err)
	}

	keyspaces, err = ts.GetKeyspaces(ctx)
	if err != nil {
		t.Errorf("GetKeyspaces: %v", err)
	}
	if len(keyspaces) != 1 || keyspaces[0] != "test_keyspace" {
		t.Errorf("GetKeyspaces: want %v, got %v", []string{"test_keyspace"}, keyspaces)
	}

	k := &pb.Keyspace{
		ShardingColumnName: "user_id",
		ShardingColumnType: pb.KeyspaceIdType_UINT64,
		ServedFroms: []*pb.Keyspace_ServedFrom{
			&pb.Keyspace_ServedFrom{
				TabletType: pb.TabletType_REPLICA,
				Cells:      []string{"c1", "c2"},
				Keyspace:   "test_keyspace3",
			},
			&pb.Keyspace_ServedFrom{
				TabletType: pb.TabletType_MASTER,
				Cells:      nil,
				Keyspace:   "test_keyspace3",
			},
		},
		SplitShardCount: 64,
	}
	if err := ts.CreateKeyspace(ctx, "test_keyspace2", k); err != nil {
		t.Errorf("CreateKeyspace: %v", err)
	}
	keyspaces, err = ts.GetKeyspaces(ctx)
	if err != nil {
		t.Errorf("GetKeyspaces: %v", err)
	}
	if len(keyspaces) != 2 ||
		keyspaces[0] != "test_keyspace" ||
		keyspaces[1] != "test_keyspace2" {
		t.Errorf("GetKeyspaces: want %v, got %v", []string{"test_keyspace", "test_keyspace2"}, keyspaces)
	}

	// Call delete shards and make sure the keyspace still exists.
	if err := ts.DeleteKeyspaceShards(ctx, "test_keyspace2"); err != nil {
		t.Errorf("DeleteKeyspaceShards: %v", err)
	}
	ki, err := ts.GetKeyspace(ctx, "test_keyspace2")
	if err != nil {
		t.Fatalf("GetKeyspace: %v", err)
	}
	if !reflect.DeepEqual(ki.Keyspace, k) {
		t.Fatalf("returned keyspace doesn't match: got %v expected %v", ki.Keyspace, k)
	}

	ki.ShardingColumnName = "other_id"
	ki.ShardingColumnType = pb.KeyspaceIdType_BYTES
	var newServedFroms []*pb.Keyspace_ServedFrom
	for _, ksf := range ki.ServedFroms {
		if ksf.TabletType == pb.TabletType_MASTER {
			continue
		}
		if ksf.TabletType == pb.TabletType_REPLICA {
			ksf.Keyspace = "test_keyspace4"
		}
		newServedFroms = append(newServedFroms, ksf)
	}
	ki.ServedFroms = newServedFroms
	err = topo.UpdateKeyspace(ctx, ts, ki)
	if err != nil {
		t.Fatalf("UpdateKeyspace: %v", err)
	}
	ki, err = ts.GetKeyspace(ctx, "test_keyspace2")
	if err != nil {
		t.Fatalf("GetKeyspace: %v", err)
	}
	if ki.ShardingColumnName != "other_id" ||
		ki.ShardingColumnType != pb.KeyspaceIdType_BYTES ||
		ki.GetServedFrom(pb.TabletType_REPLICA).Keyspace != "test_keyspace4" {
		t.Errorf("GetKeyspace: unexpected keyspace, got %v", *ki)
//.........这里部分代码省略.........

// CheckKeyspace tests the keyspace part of the API
func CheckKeyspace(ctx context.Context, t *testing.T, ts topo.Server) {
	keyspaces, err := ts.GetKeyspaces(ctx)
	if err != nil {
		t.Errorf("GetKeyspaces(empty): %v", err)
	}
	if len(keyspaces) != 0 {
		t.Errorf("len(GetKeyspaces()) != 0: %v", keyspaces)
	}

	if err := ts.CreateKeyspace(ctx, "test_keyspace", &topo.Keyspace{}); err != nil {
		t.Errorf("CreateKeyspace: %v", err)
	}
	if err := ts.CreateKeyspace(ctx, "test_keyspace", &topo.Keyspace{}); err != topo.ErrNodeExists {
		t.Errorf("CreateKeyspace(again) is not ErrNodeExists: %v", err)
	}

	// Delete and re-create.
	if err := ts.DeleteKeyspace(ctx, "test_keyspace"); err != nil {
		t.Errorf("DeleteKeyspace: %v", err)
	}
	if err := ts.CreateKeyspace(ctx, "test_keyspace", &topo.Keyspace{}); err != nil {
		t.Errorf("CreateKeyspace: %v", err)
	}

	keyspaces, err = ts.GetKeyspaces(ctx)
	if err != nil {
		t.Errorf("GetKeyspaces: %v", err)
	}
	if len(keyspaces) != 1 || keyspaces[0] != "test_keyspace" {
		t.Errorf("GetKeyspaces: want %v, got %v", []string{"test_keyspace"}, keyspaces)
	}

	k := &topo.Keyspace{
		ShardingColumnName: "user_id",
		ShardingColumnType: key.KIT_UINT64,
		ServedFromMap: map[topo.TabletType]*topo.KeyspaceServedFrom{
			topo.TYPE_REPLICA: &topo.KeyspaceServedFrom{
				Cells:    []string{"c1", "c2"},
				Keyspace: "test_keyspace3",
			},
			topo.TYPE_MASTER: &topo.KeyspaceServedFrom{
				Cells:    nil,
				Keyspace: "test_keyspace3",
			},
		},
		SplitShardCount: 64,
	}
	if err := ts.CreateKeyspace(ctx, "test_keyspace2", k); err != nil {
		t.Errorf("CreateKeyspace: %v", err)
	}
	keyspaces, err = ts.GetKeyspaces(ctx)
	if err != nil {
		t.Errorf("GetKeyspaces: %v", err)
	}
	if len(keyspaces) != 2 ||
		keyspaces[0] != "test_keyspace" ||
		keyspaces[1] != "test_keyspace2" {
		t.Errorf("GetKeyspaces: want %v, got %v", []string{"test_keyspace", "test_keyspace2"}, keyspaces)
	}

	// Call delete shards and make sure the keyspace still exists.
	if err := ts.DeleteKeyspaceShards(ctx, "test_keyspace2"); err != nil {
		t.Errorf("DeleteKeyspaceShards: %v", err)
	}
	ki, err := ts.GetKeyspace(ctx, "test_keyspace2")
	if err != nil {
		t.Fatalf("GetKeyspace: %v", err)
	}
	if !reflect.DeepEqual(ki.Keyspace, k) {
		t.Fatalf("returned keyspace doesn't match: got %v expected %v", ki.Keyspace, k)
	}

	ki.ShardingColumnName = "other_id"
	ki.ShardingColumnType = key.KIT_BYTES
	delete(ki.ServedFromMap, topo.TYPE_MASTER)
	ki.ServedFromMap[topo.TYPE_REPLICA].Keyspace = "test_keyspace4"
	err = topo.UpdateKeyspace(ctx, ts, ki)
	if err != nil {
		t.Fatalf("UpdateKeyspace: %v", err)
	}
	ki, err = ts.GetKeyspace(ctx, "test_keyspace2")
	if err != nil {
		t.Fatalf("GetKeyspace: %v", err)
	}
	if ki.ShardingColumnName != "other_id" ||
		ki.ShardingColumnType != key.KIT_BYTES ||
		ki.ServedFromMap[topo.TYPE_REPLICA].Keyspace != "test_keyspace4" {
		t.Errorf("GetKeyspace: unexpected keyspace, got %v", *ki)
	}
}

func CheckKeyspace(t *testing.T, ts topo.Server) {
	keyspaces, err := ts.GetKeyspaces()
	if err != nil {
		t.Errorf("GetKeyspaces(empty): %v", err)
	}
	if len(keyspaces) != 0 {
		t.Errorf("len(GetKeyspaces()) != 0: %v", keyspaces)
	}

	if err := ts.CreateKeyspace("test_keyspace", &topo.Keyspace{}); err != nil {
		t.Errorf("CreateKeyspace: %v", err)
	}
	if err := ts.CreateKeyspace("test_keyspace", &topo.Keyspace{}); err != topo.ErrNodeExists {
		t.Errorf("CreateKeyspace(again) is not ErrNodeExists: %v", err)
	}

	keyspaces, err = ts.GetKeyspaces()
	if err != nil {
		t.Errorf("GetKeyspaces: %v", err)
	}
	if len(keyspaces) != 1 || keyspaces[0] != "test_keyspace" {
		t.Errorf("GetKeyspaces: want %v, got %v", []string{"test_keyspace"}, keyspaces)
	}

	if err := ts.CreateKeyspace("test_keyspace2", &topo.Keyspace{
		ShardingColumnName: "user_id",
		ShardingColumnType: key.KIT_UINT64,
		ServedFrom: map[topo.TabletType]string{
			topo.TYPE_MASTER: "test_keyspace3",
		},
	}); err != nil {
		t.Errorf("CreateKeyspace: %v", err)
	}
	keyspaces, err = ts.GetKeyspaces()
	if err != nil {
		t.Errorf("GetKeyspaces: %v", err)
	}
	if len(keyspaces) != 2 ||
		keyspaces[0] != "test_keyspace" ||
		keyspaces[1] != "test_keyspace2" {
		t.Errorf("GetKeyspaces: want %v, got %v", []string{"test_keyspace", "test_keyspace2"}, keyspaces)
	}

	ki, err := ts.GetKeyspace("test_keyspace2")
	if err != nil {
		t.Fatalf("GetKeyspace: %v", err)
	}
	if ki.ShardingColumnName != "user_id" ||
		ki.ShardingColumnType != key.KIT_UINT64 ||
		ki.ServedFrom[topo.TYPE_MASTER] != "test_keyspace3" {
		t.Errorf("GetKeyspace: unexpected keyspace, got %v", *ki)
	}

	ki.ShardingColumnName = "other_id"
	ki.ShardingColumnType = key.KIT_BYTES
	delete(ki.ServedFrom, topo.TYPE_MASTER)
	ki.ServedFrom[topo.TYPE_REPLICA] = "test_keyspace4"
	err = topo.UpdateKeyspace(ts, ki)
	if err != nil {
		t.Fatalf("UpdateKeyspace: %v", err)
	}
	ki, err = ts.GetKeyspace("test_keyspace2")
	if err != nil {
		t.Fatalf("GetKeyspace: %v", err)
	}
	if ki.ShardingColumnName != "other_id" ||
		ki.ShardingColumnType != key.KIT_BYTES ||
		ki.ServedFrom[topo.TYPE_REPLICA] != "test_keyspace4" {
		t.Errorf("GetKeyspace: unexpected keyspace, got %v", *ki)
	}
}

// masterMigrateServedFrom handles the master migration. The ordering is
// a bit different than for rdonly / replica to guarantee a smooth transition.
//
// The order is as follows:
// - Add BlacklistedTables on the source shard map for master
// - Refresh the source master, so it stops writing on the tables
// - Get the source master position, wait until destination master reaches it
// - Clear SourceShard on the destination Shard
// - Refresh the destination master, so its stops its filtered
//   replication and starts accepting writes
func (wr *Wrangler) masterMigrateServedFrom(ki *topo.KeyspaceInfo, sourceShard *topo.ShardInfo, destinationShard *topo.ShardInfo, servedType topo.TabletType, tables []string, ev *events.MigrateServedFrom) error {
	// Read the data we need
	sourceMasterTabletInfo, err := wr.ts.GetTablet(sourceShard.MasterAlias)
	if err != nil {
		return err
	}
	destinationMasterTabletInfo, err := wr.ts.GetTablet(destinationShard.MasterAlias)
	if err != nil {
		return err
	}

	// Update source shard (more blacklisted tables)
	event.DispatchUpdate(ev, "updating source shard")
	if sourceShard.BlacklistedTablesMap == nil {
		sourceShard.BlacklistedTablesMap = make(map[topo.TabletType][]string)
	}
	sourceShard.BlacklistedTablesMap[servedType] = tables
	if err := topo.UpdateShard(wr.ts, sourceShard); err != nil {
		return err
	}

	// Now refresh the blacklisted table list on the source master
	event.DispatchUpdate(ev, "refreshing source master so it updates its blacklisted tables")
	if err := wr.tmc.RefreshState(sourceMasterTabletInfo, wr.ActionTimeout()); err != nil {
		return err
	}

	// get the position
	event.DispatchUpdate(ev, "getting master position")
	masterPosition, err := wr.tmc.MasterPosition(sourceMasterTabletInfo, wr.ActionTimeout())
	if err != nil {
		return err
	}

	// wait for it
	event.DispatchUpdate(ev, "waiting for destination master to catch up to source master")
	if err := wr.tmc.WaitBlpPosition(destinationMasterTabletInfo, blproto.BlpPosition{
		Uid:      0,
		Position: masterPosition,
	}, wr.ActionTimeout()); err != nil {
		return err
	}

	// Update the destination keyspace (its ServedFrom has changed)
	event.DispatchUpdate(ev, "updating keyspace")
	if err = topo.UpdateKeyspace(wr.ts, ki); err != nil {
		return err
	}

	// Update the destination shard (no more source shard)
	event.DispatchUpdate(ev, "updating destination shard")
	destinationShard.SourceShards = nil
	if err := topo.UpdateShard(wr.ts, destinationShard); err != nil {
		return err
	}

	// Tell the new shards masters they can now be read-write.
	// Invoking a remote action will also make the tablet stop filtered
	// replication.
	event.DispatchUpdate(ev, "setting destination shard masters read-write")
	if err := wr.refreshMasters([]*topo.ShardInfo{destinationShard}); err != nil {
		return err
	}

	return nil
}