// InitTablet creates or updates a tablet. If no parent is specified
// in the tablet, and the tablet has a slave type, we will find the
// appropriate parent. If createShardAndKeyspace is true and the
// parent keyspace or shard don't exist, they will be created.  If
// allowUpdate is true, and a tablet with the same ID exists, just update it.
// If a tablet is created as master, and there is already a different
// master in the shard, allowMasterOverride must be set.
func (wr *Wrangler) InitTablet(ctx context.Context, tablet *topodatapb.Tablet, allowMasterOverride, createShardAndKeyspace, allowUpdate bool) error {
	if err := topo.TabletComplete(tablet); err != nil {
		return err
	}

	// get the shard, possibly creating it
	var err error
	var si *topo.ShardInfo

	if createShardAndKeyspace {
		// create the parent keyspace and shard if needed
		si, err = wr.ts.GetOrCreateShard(ctx, tablet.Keyspace, tablet.Shard)
	} else {
		si, err = wr.ts.GetShard(ctx, tablet.Keyspace, tablet.Shard)
		if err == topo.ErrNoNode {
			return fmt.Errorf("missing parent shard, use -parent option to create it, or CreateKeyspace / CreateShard")
		}
	}

	// get the shard, checks a couple things
	if err != nil {
		return fmt.Errorf("cannot get (or create) shard %v/%v: %v", tablet.Keyspace, tablet.Shard, err)
	}
	if !key.KeyRangeEqual(si.KeyRange, tablet.KeyRange) {
		return fmt.Errorf("shard %v/%v has a different KeyRange: %v != %v", tablet.Keyspace, tablet.Shard, si.KeyRange, tablet.KeyRange)
	}
	if tablet.Type == topodatapb.TabletType_MASTER && si.HasMaster() && !topoproto.TabletAliasEqual(si.MasterAlias, tablet.Alias) && !allowMasterOverride {
		return fmt.Errorf("creating this tablet would override old master %v in shard %v/%v, use allow_master_override flag", topoproto.TabletAliasString(si.MasterAlias), tablet.Keyspace, tablet.Shard)
	}

	// update the shard record if needed
	if err := wr.updateShardCellsAndMaster(ctx, si, tablet.Alias, tablet.Type, allowMasterOverride); err != nil {
		return err
	}

	err = wr.ts.CreateTablet(ctx, tablet)
	if err == topo.ErrNodeExists && allowUpdate {
		// Try to update then
		oldTablet, err := wr.ts.GetTablet(ctx, tablet.Alias)
		if err != nil {
			return fmt.Errorf("failed reading existing tablet %v: %v", topoproto.TabletAliasString(tablet.Alias), err)
		}

		// Check we have the same keyspace / shard, and if not,
		// require the allowDifferentShard flag.
		if oldTablet.Keyspace != tablet.Keyspace || oldTablet.Shard != tablet.Shard {
			return fmt.Errorf("old tablet has shard %v/%v. Cannot override with shard %v/%v. Delete and re-add tablet if you want to change the tablet's keyspace/shard", oldTablet.Keyspace, oldTablet.Shard, tablet.Keyspace, tablet.Shard)
		}

		*(oldTablet.Tablet) = *tablet
		if err := wr.ts.UpdateTablet(ctx, oldTablet); err != nil {
			return fmt.Errorf("failed updating tablet %v: %v", topoproto.TabletAliasString(tablet.Alias), err)
		}
	}
	return nil
}

// checkShard verifies the Shard operations work correctly
func checkShard(t *testing.T, ts topo.Impl) {
	ctx := context.Background()
	tts := topo.Server{Impl: ts}

	if err := ts.CreateKeyspace(ctx, "test_keyspace", &topodatapb.Keyspace{}); err != nil {
		t.Fatalf("CreateKeyspace: %v", err)
	}

	shard := &topodatapb.Shard{
		KeyRange: newKeyRange("b0-c0"),
	}
	if err := ts.CreateShard(ctx, "test_keyspace", "b0-c0", shard); err != nil {
		t.Fatalf("CreateShard: %v", err)
	}
	if err := ts.CreateShard(ctx, "test_keyspace", "b0-c0", shard); err != topo.ErrNodeExists {
		t.Errorf("CreateShard called second time, got: %v", err)
	}

	// Delete shard and see if we can re-create it.
	if err := ts.DeleteShard(ctx, "test_keyspace", "b0-c0"); err != nil {
		t.Fatalf("DeleteShard: %v", err)
	}
	if err := ts.CreateShard(ctx, "test_keyspace", "b0-c0", shard); err != nil {
		t.Fatalf("CreateShard: %v", err)
	}

	// Delete ALL shards.
	if err := ts.DeleteKeyspaceShards(ctx, "test_keyspace"); err != nil {
		t.Fatalf("DeleteKeyspaceShards: %v", err)
	}
	if err := ts.CreateShard(ctx, "test_keyspace", "b0-c0", shard); err != nil {
		t.Fatalf("CreateShard: %v", err)
	}

	if _, _, err := ts.GetShard(ctx, "test_keyspace", "666"); err != topo.ErrNoNode {
		t.Errorf("GetShard(666): %v", err)
	}

	shard, version, err := ts.GetShard(ctx, "test_keyspace", "b0-c0")
	if err != nil {
		t.Errorf("GetShard: %v", err)
	}
	if want := newKeyRange("b0-c0"); !key.KeyRangeEqual(shard.KeyRange, want) {
		t.Errorf("shard.KeyRange: want %v, got %v", want, shard.KeyRange)
	}
	master := &topodatapb.TabletAlias{Cell: "ny", Uid: 1}
	shard.MasterAlias = master
	shard.KeyRange = newKeyRange("b0-c0")
	shard.ServedTypes = []*topodatapb.Shard_ServedType{
		{
			TabletType: topodatapb.TabletType_MASTER,
		},
		{
			TabletType: topodatapb.TabletType_REPLICA,
			Cells:      []string{"c1"},
		},
		{
			TabletType: topodatapb.TabletType_RDONLY,
		},
	}
	shard.SourceShards = []*topodatapb.Shard_SourceShard{
		{
			Uid:      1,
			Keyspace: "source_ks",
			Shard:    "b8-c0",
			KeyRange: newKeyRange("b8-c0"),
			Tables:   []string{"table1", "table2"},
		},
	}
	shard.TabletControls = []*topodatapb.Shard_TabletControl{
		{
			TabletType:        topodatapb.TabletType_MASTER,
			Cells:             []string{"c1", "c2"},
			BlacklistedTables: []string{"black1", "black2"},
		},
		{
			TabletType:          topodatapb.TabletType_REPLICA,
			DisableQueryService: true,
		},
	}
	if _, err := ts.UpdateShard(ctx, "test_keyspace", "b0-c0", shard, version); err != nil {
		t.Errorf("UpdateShard: %v", err)
	}

	other := &topodatapb.TabletAlias{Cell: "ny", Uid: 82873}
	_, err = tts.UpdateShardFields(ctx, "test_keyspace", "b0-c0", func(si *topo.ShardInfo) error {
		si.MasterAlias = other
		return nil
	})
	if err != nil {
		t.Fatalf("UpdateShardFields error: %v", err)
	}

	s, _, err := ts.GetShard(ctx, "test_keyspace", "b0-c0")
	if err != nil {
		t.Fatalf("GetShard: %v", err)
	}
	if *s.MasterAlias != *other {
		t.Fatalf("shard.MasterAlias = %v, want %v", s.MasterAlias, other)
//.........这里部分代码省略.........

//.........这里部分代码省略.........
	if err := ts.UpdateEndPoints(ctx, cell, "test_keyspace", "-10", topodatapb.TabletType_MASTER, endPoints, version+1); err != topo.ErrBadVersion {
		t.Fatalf("UpdateEndPoints(master): err = %v, want topo.ErrBadVersion", err)
	}
	// Update with the right version.
	if err := ts.UpdateEndPoints(ctx, cell, "test_keyspace", "-10", topodatapb.TabletType_MASTER, endPoints, version); err != nil {
		t.Fatalf("UpdateEndPoints(master): %v", err)
	}
	// Update existing EndPoints unconditionally.
	if err := ts.UpdateEndPoints(ctx, cell, "test_keyspace", "-10", topodatapb.TabletType_MASTER, endPoints, -1); err != nil {
		t.Fatalf("UpdateEndPoints(master): %v", err)
	}

	if err := ts.DeleteEndPoints(ctx, cell, "test_keyspace", "-10", topodatapb.TabletType_REPLICA, -1); err != topo.ErrNoNode {
		t.Errorf("DeleteEndPoints(unknown): %v", err)
	}
	if err := ts.DeleteEndPoints(ctx, cell, "test_keyspace", "-10", topodatapb.TabletType_MASTER, -1); err != nil {
		t.Errorf("DeleteEndPoints(master): %v", err)
	}

	// test cell/keyspace/shard entries (SrvShard)
	srvShard := &topodatapb.SrvShard{
		Name:       "-10",
		KeyRange:   newKeyRange("-10"),
		MasterCell: "test",
	}
	if err := ts.UpdateSrvShard(ctx, cell, "test_keyspace", "-10", srvShard); err != nil {
		t.Fatalf("UpdateSrvShard(1): %v", err)
	}
	if _, err := ts.GetSrvShard(ctx, cell, "test_keyspace", "666"); err != topo.ErrNoNode {
		t.Errorf("GetSrvShard(invalid): %v", err)
	}
	if s, err := ts.GetSrvShard(ctx, cell, "test_keyspace", "-10"); err != nil ||
		s.Name != "-10" ||
		!key.KeyRangeEqual(s.KeyRange, newKeyRange("-10")) ||
		s.MasterCell != "test" {
		t.Errorf("GetSrvShard(valid): %v", err)
	}

	// test cell/keyspace entries (SrvKeyspace)
	srvKeyspace := topodatapb.SrvKeyspace{
		Partitions: []*topodatapb.SrvKeyspace_KeyspacePartition{
			&topodatapb.SrvKeyspace_KeyspacePartition{
				ServedType: topodatapb.TabletType_MASTER,
				ShardReferences: []*topodatapb.ShardReference{
					&topodatapb.ShardReference{
						Name: "-80",
						KeyRange: &topodatapb.KeyRange{
							End: []byte{0x80},
						},
					},
				},
			},
		},
		ShardingColumnName: "video_id",
		ShardingColumnType: topodatapb.KeyspaceIdType_UINT64,
		ServedFrom: []*topodatapb.SrvKeyspace_ServedFrom{
			&topodatapb.SrvKeyspace_ServedFrom{
				TabletType: topodatapb.TabletType_REPLICA,
				Keyspace:   "other_keyspace",
			},
		},
	}
	if err := ts.UpdateSrvKeyspace(ctx, cell, "test_keyspace", &srvKeyspace); err != nil {
		t.Errorf("UpdateSrvKeyspace(1): %v", err)
	}
	if _, err := ts.GetSrvKeyspace(ctx, cell, "test_keyspace666"); err != topo.ErrNoNode {

// InitTablet creates or updates a tablet. If no parent is specified
// in the tablet, and the tablet has a slave type, we will find the
// appropriate parent. If createShardAndKeyspace is true and the
// parent keyspace or shard don't exist, they will be created.  If
// update is true, and a tablet with the same ID exists, update it.
// If Force is true, and a tablet with the same ID already exists, it
// will be scrapped and deleted, and then recreated.
func (wr *Wrangler) InitTablet(ctx context.Context, tablet *pb.Tablet, force, createShardAndKeyspace, update bool) error {
	if err := topo.TabletComplete(tablet); err != nil {
		return err
	}

	if topo.IsInReplicationGraph(tablet.Type) {
		// get the shard, possibly creating it
		var err error
		var si *topo.ShardInfo

		if createShardAndKeyspace {
			// create the parent keyspace and shard if needed
			si, err = topotools.GetOrCreateShard(ctx, wr.ts, tablet.Keyspace, tablet.Shard)
		} else {
			si, err = wr.ts.GetShard(ctx, tablet.Keyspace, tablet.Shard)
			if err == topo.ErrNoNode {
				return fmt.Errorf("missing parent shard, use -parent option to create it, or CreateKeyspace / CreateShard")
			}
		}

		// get the shard, checks a couple things
		if err != nil {
			return fmt.Errorf("cannot get (or create) shard %v/%v: %v", tablet.Keyspace, tablet.Shard, err)
		}
		if !key.KeyRangeEqual(si.KeyRange, tablet.KeyRange) {
			return fmt.Errorf("shard %v/%v has a different KeyRange: %v != %v", tablet.Keyspace, tablet.Shard, si.KeyRange, tablet.KeyRange)
		}
		if tablet.Type == pb.TabletType_MASTER && !topo.TabletAliasIsZero(si.MasterAlias) && !topo.TabletAliasEqual(si.MasterAlias, tablet.Alias) && !force {
			return fmt.Errorf("creating this tablet would override old master %v in shard %v/%v", topo.TabletAliasString(si.MasterAlias), tablet.Keyspace, tablet.Shard)
		}

		// update the shard record if needed
		if err := wr.updateShardCellsAndMaster(ctx, si, tablet.Alias, tablet.Type, force); err != nil {
			return err
		}
	}

	err := topo.CreateTablet(ctx, wr.ts, tablet)
	if err != nil && err == topo.ErrNodeExists {
		// Try to update nicely, but if it fails fall back to force behavior.
		if update || force {
			oldTablet, err := wr.ts.GetTablet(ctx, tablet.Alias)
			if err != nil {
				wr.Logger().Warningf("failed reading tablet %v: %v", topo.TabletAliasString(tablet.Alias), err)
			} else {
				if oldTablet.Keyspace == tablet.Keyspace && oldTablet.Shard == tablet.Shard {
					*(oldTablet.Tablet) = *tablet
					if err := topo.UpdateTablet(ctx, wr.ts, oldTablet); err != nil {
						wr.Logger().Warningf("failed updating tablet %v: %v", topo.TabletAliasString(tablet.Alias), err)
						// now fall through the Scrap case
					} else {
						if !topo.IsInReplicationGraph(tablet.Type) {
							return nil
						}

						if err := topo.UpdateTabletReplicationData(ctx, wr.ts, tablet); err != nil {
							wr.Logger().Warningf("failed updating tablet replication data for %v: %v", topo.TabletAliasString(tablet.Alias), err)
							// now fall through the Scrap case
						} else {
							return nil
						}
					}
				}
			}
		}
		if force {
			if err = wr.Scrap(ctx, tablet.Alias, force, false); err != nil {
				wr.Logger().Errorf("failed scrapping tablet %v: %v", topo.TabletAliasString(tablet.Alias), err)
				return err
			}
			if err := wr.ts.DeleteTablet(ctx, tablet.Alias); err != nil {
				// we ignore this
				wr.Logger().Errorf("failed deleting tablet %v: %v", topo.TabletAliasString(tablet.Alias), err)
			}
			return topo.CreateTablet(ctx, wr.ts, tablet)
		}
	}
	return err
}

func (sdw *SplitDiffWorker) diff(ctx context.Context) error {
	sdw.SetState(WorkerStateDiff)

	sdw.wr.Logger().Infof("Gathering schema information...")
	wg := sync.WaitGroup{}
	rec := &concurrency.AllErrorRecorder{}
	wg.Add(1)
	go func() {
		var err error
		shortCtx, cancel := context.WithTimeout(ctx, *remoteActionsTimeout)
		sdw.destinationSchemaDefinition, err = sdw.wr.GetSchema(
			shortCtx, sdw.destinationAlias, nil /* tables */, sdw.excludeTables, false /* includeViews */)
		cancel()
		rec.RecordError(err)
		sdw.wr.Logger().Infof("Got schema from destination %v", sdw.destinationAlias)
		wg.Done()
	}()
	wg.Add(1)
	go func() {
		var err error
		shortCtx, cancel := context.WithTimeout(ctx, *remoteActionsTimeout)
		sdw.sourceSchemaDefinition, err = sdw.wr.GetSchema(
			shortCtx, sdw.sourceAlias, nil /* tables */, sdw.excludeTables, false /* includeViews */)
		cancel()
		rec.RecordError(err)
		sdw.wr.Logger().Infof("Got schema from source %v", sdw.sourceAlias)
		wg.Done()
	}()

	wg.Wait()
	if rec.HasErrors() {
		return rec.Error()
	}

	sdw.wr.Logger().Infof("Diffing the schema...")
	rec = &concurrency.AllErrorRecorder{}
	tmutils.DiffSchema("destination", sdw.destinationSchemaDefinition, "source", sdw.sourceSchemaDefinition, rec)
	if rec.HasErrors() {
		sdw.wr.Logger().Warningf("Different schemas: %v", rec.Error().Error())
	} else {
		sdw.wr.Logger().Infof("Schema match, good.")
	}

	// read the vschema if needed
	var keyspaceSchema *vindexes.KeyspaceSchema
	if *useV3ReshardingMode {
		kschema, err := sdw.wr.TopoServer().GetVSchema(ctx, sdw.keyspace)
		if err != nil {
			return fmt.Errorf("cannot load VSchema for keyspace %v: %v", sdw.keyspace, err)
		}
		if kschema == nil {
			return fmt.Errorf("no VSchema for keyspace %v", sdw.keyspace)
		}

		keyspaceSchema, err = vindexes.BuildKeyspaceSchema(kschema, sdw.keyspace)
		if err != nil {
			return fmt.Errorf("cannot build vschema for keyspace %v: %v", sdw.keyspace, err)
		}
	}

	// Compute the overlap keyrange. Later, we'll compare it with
	// source or destination keyrange. If it matches either,
	// we'll just ask for all the data. If the overlap is a subset,
	// we'll filter.
	overlap, err := key.KeyRangesOverlap(sdw.shardInfo.KeyRange, sdw.shardInfo.SourceShards[sdw.sourceUID].KeyRange)
	if err != nil {
		return fmt.Errorf("Source shard doesn't overlap with destination: %v", err)
	}

	// run the diffs, 8 at a time
	sdw.wr.Logger().Infof("Running the diffs...")
	// TODO(mberlin): Parameterize the hard coded value 8.
	sem := sync2.NewSemaphore(8, 0)
	for _, tableDefinition := range sdw.destinationSchemaDefinition.TableDefinitions {
		wg.Add(1)
		go func(tableDefinition *tabletmanagerdatapb.TableDefinition) {
			defer wg.Done()
			sem.Acquire()
			defer sem.Release()

			sdw.wr.Logger().Infof("Starting the diff on table %v", tableDefinition.Name)

			// On the source, see if we need a full scan
			// or a filtered scan.
			var sourceQueryResultReader *QueryResultReader
			if key.KeyRangeEqual(overlap, sdw.shardInfo.SourceShards[sdw.sourceUID].KeyRange) {
				sourceQueryResultReader, err = TableScan(ctx, sdw.wr.Logger(), sdw.wr.TopoServer(), sdw.sourceAlias, tableDefinition)
			} else {
				sourceQueryResultReader, err = TableScanByKeyRange(ctx, sdw.wr.Logger(), sdw.wr.TopoServer(), sdw.sourceAlias, tableDefinition, overlap, keyspaceSchema, sdw.keyspaceInfo.ShardingColumnName, sdw.keyspaceInfo.ShardingColumnType)
			}
			if err != nil {
				newErr := fmt.Errorf("TableScan(ByKeyRange?)(source) failed: %v", err)
				rec.RecordError(newErr)
				sdw.wr.Logger().Errorf("%v", newErr)
				return
			}
			defer sourceQueryResultReader.Close(ctx)

			// On the destination, see if we need a full scan
			// or a filtered scan.
//.........这里部分代码省略.........