示例#1
0
// 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, 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 err := sourceShard.UpdateSourceBlacklistedTables(topo.TYPE_MASTER, nil, false, tables); err != nil {
		return fmt.Errorf("UpdateSourceBlacklistedTables(%v/%v) failed: %v", sourceShard.Keyspace(), sourceShard.ShardName(), err)
	}
	if err := topo.UpdateShard(context.TODO(), 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(wr.ctx, sourceMasterTabletInfo); err != nil {
		return err
	}

	// get the position
	event.DispatchUpdate(ev, "getting master position")
	masterPosition, err := wr.tmc.MasterPosition(wr.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(context.TODO(), 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(context.TODO(), 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
}