func (agent *ActionAgent) allowQueries(tablet *topo.Tablet, blacklistedTables []string) error {
	// if the query service is already running, we're not starting it again
	if agent.QueryServiceControl.IsServing() {
		return nil
	}

	// only for real instances
	if agent.DBConfigs != nil {
		// Update our DB config to match the info we have in the tablet
		if agent.DBConfigs.App.DbName == "" {
			agent.DBConfigs.App.DbName = tablet.DbName()
		}
		agent.DBConfigs.App.Keyspace = tablet.Keyspace
		agent.DBConfigs.App.Shard = tablet.Shard
		if tablet.Type != topo.TYPE_MASTER {
			agent.DBConfigs.App.EnableInvalidator = true
		} else {
			agent.DBConfigs.App.EnableInvalidator = false
		}
	}

	err := agent.loadKeyspaceAndBlacklistRules(tablet, blacklistedTables)
	if err != nil {
		return err
	}

	return agent.QueryServiceControl.AllowQueries(&pb.Target{
		Keyspace:   tablet.Keyspace,
		Shard:      tablet.Shard,
		TabletType: topo.TabletTypeToProto(tablet.Type),
	}, agent.DBConfigs, agent.SchemaOverrides, agent.MysqlDaemon)
}

// RefreshMap reads the right data from topo.Server and makes sure
// we're playing the right logs
func (blm *BinlogPlayerMap) RefreshMap(tablet topo.Tablet) {
	log.Infof("Refreshing map of binlog players")

	// read the shard to get SourceShards
	shardInfo, err := blm.ts.GetShard(tablet.Keyspace, tablet.Shard)
	if err != nil {
		log.Errorf("Cannot read shard for this tablet: %v", tablet.Alias())
		return
	}

	// get the existing sources and build a map of sources to remove
	toRemove := make(map[topo.SourceShard]bool)
	for source, _ := range blm.players {
		toRemove[source] = true
	}

	// for each source, add it if not there, and delete from toRemove
	for _, source := range shardInfo.SourceShards {
		blm.AddPlayer(tablet.Keyspace, source)
		delete(toRemove, source)
	}

	// remove all entries from toRemove
	for source, _ := range toRemove {
		blm.players[source].Stop()
		delete(blm.players, source)
	}
}

// AddTablet adds a new tablet to the topology and starts its event
// loop.
func (fix *Fixture) AddTablet(uid int, cell string, tabletType topo.TabletType, master *topo.Tablet) *topo.Tablet {
	tablet := &topo.Tablet{
		Alias:    topo.TabletAlias{Cell: cell, Uid: uint32(uid)},
		Hostname: fmt.Sprintf("%vbsr%v", cell, uid),
		IPAddr:   fmt.Sprintf("212.244.218.%v", uid),
		Portmap: map[string]int{
			"vt":    3333 + 10*uid,
			"mysql": 3334 + 10*uid,
		},
		Keyspace: TestKeyspace,
		Type:     tabletType,
		Shard:    TestShard,
		KeyRange: newKeyRange(TestShard),
	}
	if master != nil {
		tablet.Parent = master.Alias
	}

	if err := fix.Wrangler.InitTablet(tablet, true, true, false); err != nil {
		fix.Fatalf("CreateTablet: %v", err)
	}
	mysqlDaemon := &mysqlctl.FakeMysqlDaemon{}
	if master != nil {
		mysqlDaemon.MasterAddr = master.GetMysqlIpAddr()
	}
	mysqlDaemon.MysqlPort = 3334 + 10*uid

	pack := &tabletPack{Tablet: tablet, mysql: mysqlDaemon}
	fix.startFakeTabletActionLoop(pack)

	fix.tablets[uid] = pack

	return tablet
}

func (agent *ActionAgent) allowQueries(tablet *topo.Tablet) error {
	if agent.DBConfigs == nil {
		// test instance, do nothing
		return nil
	}

	// if the query service is already running, we're not starting it again
	if tabletserver.SqlQueryRpcService.GetState() == "SERVING" {
		return nil
	}

	// Update our DB config to match the info we have in the tablet
	if agent.DBConfigs.App.DbName == "" {
		agent.DBConfigs.App.DbName = tablet.DbName()
	}
	agent.DBConfigs.App.Keyspace = tablet.Keyspace
	agent.DBConfigs.App.Shard = tablet.Shard

	qrs, err := agent.createQueryRules(tablet)
	if err != nil {
		return err
	}

	return tabletserver.AllowQueries(&agent.DBConfigs.App, agent.SchemaOverrides, qrs, agent.Mysqld, false)
}

func (zkts *Server) CreateTablet(tablet *topo.Tablet) error {
	zkTabletPath := TabletPathForAlias(tablet.Alias())

	// Create /zk/<cell>/vt/tablets/<uid>
	_, err := zk.CreateRecursive(zkts.zconn, zkTabletPath, tablet.Json(), 0, zookeeper.WorldACL(zookeeper.PERM_ALL))
	if err != nil {
		if zookeeper.IsError(err, zookeeper.ZNODEEXISTS) {
			err = topo.ErrNodeExists
		}
		return err
	}

	// Create /zk/<cell>/vt/tablets/<uid>/action
	tap := path.Join(zkTabletPath, "action")
	_, err = zkts.zconn.Create(tap, "", 0, zookeeper.WorldACL(zookeeper.PERM_ALL))
	if err != nil {
		return err
	}

	// Create /zk/<cell>/vt/tablets/<uid>/actionlog
	talp := path.Join(zkTabletPath, "actionlog")
	_, err = zkts.zconn.Create(talp, "", 0, zookeeper.WorldACL(zookeeper.PERM_ALL))
	if err != nil {
		return err
	}

	return nil
}

// UpdateTabletEndpoints fixes up any entries in the serving graph that relate
// to a given tablet.
func UpdateTabletEndpoints(ctx context.Context, ts topo.Server, tablet *topo.Tablet) (err error) {
	if *lockSrvShard {
		// This lock is only necessary until all tablets are upgraded to lock-free.
		actionNode := actionnode.RebuildSrvShard()
		lockPath, err := actionNode.LockSrvShard(ctx, ts, tablet.Alias.Cell, tablet.Keyspace, tablet.Shard)
		if err != nil {
			return fmt.Errorf("can't lock shard for UpdateTabletEndpoints(%v): %v", tablet, err)
		}

		defer func() {
			actionNode.UnlockSrvShard(ctx, ts, tablet.Alias.Cell, tablet.Keyspace, tablet.Shard, lockPath, err)
		}()
	}

	srvTypes, err := ts.GetSrvTabletTypesPerShard(ctx, tablet.Alias.Cell, tablet.Keyspace, tablet.Shard)
	if err != nil {
		if err != topo.ErrNoNode {
			return err
		}
		// It's fine if there are no existing types.
		srvTypes = nil
	}

	wg := sync.WaitGroup{}
	errs := concurrency.AllErrorRecorder{}

	// Update the list that the tablet is supposed to be in (if any).
	if tablet.IsInServingGraph() {
		endpoint, err := tablet.EndPoint()
		if err != nil {
			return err
		}

		wg.Add(1)
		go func() {
			defer wg.Done()
			errs.RecordError(
				updateEndpoint(ctx, ts, tablet.Alias.Cell, tablet.Keyspace, tablet.Shard,
					tablet.Type, endpoint))
		}()
	}

	// Remove it from any other lists it isn't supposed to be in.
	for _, srvType := range srvTypes {
		if srvType != tablet.Type {
			wg.Add(1)
			go func(tabletType topo.TabletType) {
				defer wg.Done()
				errs.RecordError(
					removeEndpoint(ctx, ts, tablet.Alias.Cell, tablet.Keyspace, tablet.Shard,
						tabletType, tablet.Alias.Uid))
			}(srvType)
		}
	}

	wg.Wait()
	return errs.Error()
}

// loadKeyspaceAndBlacklistRules does what the name suggests:
// 1. load and build keyrange query rules
// 2. load and build blacklist query rules
func (agent *ActionAgent) loadKeyspaceAndBlacklistRules(tablet *topo.Tablet, blacklistedTables []string) (err error) {
	// Keyrange rules
	keyrangeRules := tabletserver.NewQueryRules()
	if tablet.KeyRange.IsPartial() {
		log.Infof("Restricting to keyrange: %v", tablet.KeyRange)
		dmlPlans := []struct {
			planID   planbuilder.PlanType
			onAbsent bool
		}{
			{planbuilder.PLAN_INSERT_PK, true},
			{planbuilder.PLAN_INSERT_SUBQUERY, true},
			{planbuilder.PLAN_PASS_DML, false},
			{planbuilder.PLAN_DML_PK, false},
			{planbuilder.PLAN_DML_SUBQUERY, false},
		}
		for _, plan := range dmlPlans {
			qr := tabletserver.NewQueryRule(
				fmt.Sprintf("enforce keyspace_id range for %v", plan.planID),
				fmt.Sprintf("keyspace_id_not_in_range_%v", plan.planID),
				tabletserver.QR_FAIL,
			)
			qr.AddPlanCond(plan.planID)
			err := qr.AddBindVarCond("keyspace_id", plan.onAbsent, true, tabletserver.QR_NOTIN, tablet.KeyRange)
			if err != nil {
				return fmt.Errorf("Unable to add keyspace rule: %v", err)
			}
			keyrangeRules.Add(qr)
		}
	}

	// Blacklisted tables
	blacklistRules := tabletserver.NewQueryRules()
	if len(blacklistedTables) > 0 {
		// tables, first resolve wildcards
		tables, err := mysqlctl.ResolveTables(agent.MysqlDaemon, tablet.DbName(), blacklistedTables)
		if err != nil {
			return err
		}
		log.Infof("Blacklisting tables %v", strings.Join(tables, ", "))
		qr := tabletserver.NewQueryRule("enforce blacklisted tables", "blacklisted_table", tabletserver.QR_FAIL_RETRY)
		for _, t := range tables {
			qr.AddTableCond(t)
		}
		blacklistRules.Add(qr)
	}
	// Push all three sets of QueryRules to SqlQueryRpcService
	loadRuleErr := agent.QueryServiceControl.SetQueryRules(keyrangeQueryRules, keyrangeRules)
	if loadRuleErr != nil {
		log.Warningf("Fail to load query rule set %s: %s", keyrangeQueryRules, loadRuleErr)
	}

	loadRuleErr = agent.QueryServiceControl.SetQueryRules(blacklistQueryRules, blacklistRules)
	if loadRuleErr != nil {
		log.Warningf("Fail to load query rule set %s: %s", blacklistQueryRules, loadRuleErr)
	}
	return nil
}

func (tee *Tee) CreateTablet(tablet *topo.Tablet) error {
	err := tee.primary.CreateTablet(tablet)
	if err != nil && err != topo.ErrNodeExists {
		return err
	}

	if err := tee.primary.CreateTablet(tablet); err != nil && err != topo.ErrNodeExists {
		// not critical enough to fail
		relog.Warning("secondary.CreateTablet(%v) failed: %v", tablet.Alias(), err)
	}
	return err
}

func EndPointForTablet(tablet *topo.Tablet) (*topo.EndPoint, error) {
	entry := topo.NewAddr(tablet.Alias.Uid, tablet.Hostname)
	if err := tablet.ValidatePortmap(); err != nil {
		return nil, err
	}

	// TODO(szopa): Rename _vtocc to vt.
	entry.NamedPortMap = map[string]int{
		"_vtocc": tablet.Portmap["vt"],
		"_mysql": tablet.Portmap["mysql"],
	}
	if port, ok := tablet.Portmap["vts"]; ok {
		entry.NamedPortMap["_vts"] = port
	}
	return entry, nil
}

func (agent *ActionAgent) allowQueries(tablet *topo.Tablet) error {
	// if the query service is already running, we're not starting it again
	if tabletserver.SqlQueryRpcService.GetState() == "SERVING" {
		return nil
	}

	// Update our DB config to match the info we have in the tablet
	if agent.DBConfigs.App.DbName == "" {
		agent.DBConfigs.App.DbName = tablet.DbName()
	}
	agent.DBConfigs.App.Keyspace = tablet.Keyspace
	agent.DBConfigs.App.Shard = tablet.Shard
	if tablet.Type != topo.TYPE_MASTER {
		agent.DBConfigs.App.EnableInvalidator = true
	} else {
		agent.DBConfigs.App.EnableInvalidator = false
	}

	// Compute the query rules that match the tablet record
	qrs := tabletserver.LoadCustomRules()
	if tablet.KeyRange.IsPartial() {
		qr := tabletserver.NewQueryRule("enforce keyspace_id range", "keyspace_id_not_in_range", tabletserver.QR_FAIL)
		qr.AddPlanCond(planbuilder.PLAN_INSERT_PK)
		err := qr.AddBindVarCond("keyspace_id", true, true, tabletserver.QR_NOTIN, tablet.KeyRange)
		if err != nil {
			log.Warningf("Unable to add keyspace rule: %v", err)
		} else {
			qrs.Add(qr)
		}
	}
	if len(tablet.BlacklistedTables) > 0 {
		// tables, first resolve wildcards
		tables, err := agent.Mysqld.ResolveTables(tablet.DbName(), tablet.BlacklistedTables)
		if err != nil {
			log.Warningf("Unable to resolve blacklisted tables: %v", err)
		} else {
			log.Infof("Blacklisting tables %v", strings.Join(tables, ", "))
			qr := tabletserver.NewQueryRule("enforce blacklisted tables", "blacklisted_table", tabletserver.QR_FAIL_RETRY)
			for _, t := range tables {
				qr.AddTableCond(t)
			}
			qrs.Add(qr)
		}
	}

	return tabletserver.AllowQueries(&agent.DBConfigs.App, agent.SchemaOverrides, qrs, agent.Mysqld, false)
}

// createQueryRules computes the query rules that match the tablet record
func (agent *ActionAgent) createQueryRules(tablet *topo.Tablet) (qrs *tabletserver.QueryRules, err error) {
	qrs = tabletserver.LoadCustomRules()

	// Keyrange rules
	if tablet.KeyRange.IsPartial() {
		log.Infof("Restricting to keyrange: %v", tablet.KeyRange)
		dml_plans := []struct {
			planID   planbuilder.PlanType
			onAbsent bool
		}{
			{planbuilder.PLAN_INSERT_PK, true},
			{planbuilder.PLAN_INSERT_SUBQUERY, true},
			{planbuilder.PLAN_PASS_DML, false},
			{planbuilder.PLAN_DML_PK, false},
			{planbuilder.PLAN_DML_SUBQUERY, false},
		}
		for _, plan := range dml_plans {
			qr := tabletserver.NewQueryRule(
				fmt.Sprintf("enforce keyspace_id range for %v", plan.planID),
				fmt.Sprintf("keyspace_id_not_in_range_%v", plan.planID),
				tabletserver.QR_FAIL,
			)
			qr.AddPlanCond(plan.planID)
			err := qr.AddBindVarCond("keyspace_id", plan.onAbsent, true, tabletserver.QR_NOTIN, tablet.KeyRange)
			if err != nil {
				return nil, fmt.Errorf("Unable to add keyspace rule: %v", err)
			}
			qrs.Add(qr)
		}
	}

	// Blacklisted tables
	if len(tablet.BlacklistedTables) > 0 {
		// tables, first resolve wildcards
		tables, err := agent.Mysqld.ResolveTables(tablet.DbName(), tablet.BlacklistedTables)
		if err != nil {
			return nil, err
		}
		log.Infof("Blacklisting tables %v", strings.Join(tables, ", "))
		qr := tabletserver.NewQueryRule("enforce blacklisted tables", "blacklisted_table", tabletserver.QR_FAIL_RETRY)
		for _, t := range tables {
			qr.AddTableCond(t)
		}
		qrs.Add(qr)
	}
	return qrs, nil
}

// UpdateTabletEndpoints fixes up any entries in the serving graph that relate
// to a given tablet.
func UpdateTabletEndpoints(ctx context.Context, ts topo.Server, tablet *topo.Tablet) (err error) {
	srvTypes, err := ts.GetSrvTabletTypesPerShard(ctx, tablet.Alias.Cell, tablet.Keyspace, tablet.Shard)
	if err != nil {
		if err != topo.ErrNoNode {
			return err
		}
		// It's fine if there are no existing types.
		srvTypes = nil
	}

	wg := sync.WaitGroup{}
	errs := concurrency.AllErrorRecorder{}

	// Update the list that the tablet is supposed to be in (if any).
	if tablet.IsInServingGraph() {
		endpoint, err := tablet.EndPoint()
		if err != nil {
			return err
		}

		wg.Add(1)
		go func() {
			defer wg.Done()
			errs.RecordError(
				updateEndpoint(ctx, ts, tablet.Alias.Cell, tablet.Keyspace, tablet.Shard,
					tablet.Type, endpoint))
		}()
	}

	// Remove it from any other lists it isn't supposed to be in.
	for _, srvType := range srvTypes {
		if srvType != tablet.Type {
			wg.Add(1)
			go func(tabletType topo.TabletType) {
				defer wg.Done()
				errs.RecordError(
					removeEndpoint(ctx, ts, tablet.Alias.Cell, tablet.Keyspace, tablet.Shard,
						tabletType, tablet.Alias.Uid))
			}(srvType)
		}
	}

	wg.Wait()
	return errs.Error()
}

// RefreshMap reads the right data from topo.Server and makes sure
// we're playing the right logs.
func (blm *BinlogPlayerMap) RefreshMap(ctx context.Context, tablet *topo.Tablet, keyspaceInfo *topo.KeyspaceInfo, shardInfo *topo.ShardInfo) {
	log.Infof("Refreshing map of binlog players")
	if shardInfo == nil {
		log.Warningf("Could not read shardInfo, not changing anything")
		return
	}

	if len(shardInfo.SourceShards) > 0 && keyspaceInfo == nil {
		log.Warningf("Could not read keyspaceInfo, not changing anything")
		return
	}

	blm.mu.Lock()
	if blm.dbConfig.DbName == "" {
		blm.dbConfig.DbName = tablet.DbName()
	}

	// get the existing sources and build a map of sources to remove
	toRemove := make(map[uint32]bool)
	hadPlayers := false
	for source := range blm.players {
		toRemove[source] = true
		hadPlayers = true
	}

	// for each source, add it if not there, and delete from toRemove
	for _, sourceShard := range shardInfo.SourceShards {
		blm.addPlayer(ctx, tablet.Alias.Cell, keyspaceInfo.ShardingColumnType, key.KeyRangeToProto(tablet.KeyRange), sourceShard, tablet.DbName())
		delete(toRemove, sourceShard.Uid)
	}
	hasPlayers := len(shardInfo.SourceShards) > 0

	// remove all entries from toRemove
	for source := range toRemove {
		blm.players[source].Stop()
		delete(blm.players, source)
	}

	blm.mu.Unlock()

	if hadPlayers && !hasPlayers {
		// We're done streaming, so turn off special playback settings.
		blm.mysqld.DisableBinlogPlayback()
	}
}

// CreateTablet is part of the topo.Server interface
func (zkts *Server) CreateTablet(ctx context.Context, tablet *topo.Tablet) error {
	zkTabletPath := TabletPathForAlias(tablet.Alias)

	// Create /zk/<cell>/vt/tablets/<uid>
	_, err := zk.CreateRecursive(zkts.zconn, zkTabletPath, tablet.JSON(), 0, zookeeper.WorldACL(zookeeper.PERM_ALL))
	if err != nil {
		if zookeeper.IsError(err, zookeeper.ZNODEEXISTS) {
			err = topo.ErrNodeExists
		}
		return err
	}

	event.Dispatch(&events.TabletChange{
		Tablet: *tablet,
		Status: "created",
	})
	return nil
}

// RefreshMap reads the right data from topo.Server and makes sure
// we're playing the right logs
func (blm *BinlogPlayerMap) RefreshMap(tablet topo.Tablet) {
	log.Infof("Refreshing map of binlog players")

	// read the shard to get SourceShards
	shardInfo, err := blm.ts.GetShard(tablet.Keyspace, tablet.Shard)
	if err != nil {
		log.Errorf("Cannot read shard for this tablet: %v", tablet.Alias())
		return
	}

	blm.mu.Lock()

	// get the existing sources and build a map of sources to remove
	toRemove := make(map[topo.SourceShard]bool)
	hadPlayers := false
	for source, _ := range blm.players {
		toRemove[source] = true
		hadPlayers = true
	}

	// for each source, add it if not there, and delete from toRemove
	for _, sourceShard := range shardInfo.SourceShards {
		blm.addPlayer(tablet.Cell, tablet.KeyRange, sourceShard)
		delete(toRemove, sourceShard)
	}
	hasPlayers := len(shardInfo.SourceShards) > 0

	// remove all entries from toRemove
	for source, _ := range toRemove {
		blm.players[source].Stop()
		delete(blm.players, source)
	}

	blm.mu.Unlock()

	if hadPlayers && !hasPlayers {
		blm.EnableSuperToSetTimestamp()
	}
}

// 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(tablet *topo.Tablet, force, createShardAndKeyspace, update bool) error {
	if err := tablet.Complete(); err != nil {
		return err
	}

	if tablet.IsInReplicationGraph() {
		// create the parent keyspace and shard if needed
		if createShardAndKeyspace {
			if err := wr.ts.CreateKeyspace(tablet.Keyspace, &topo.Keyspace{}); err != nil && err != topo.ErrNodeExists {
				return err
			}

			if err := topo.CreateShard(wr.ts, tablet.Keyspace, tablet.Shard); err != nil && err != topo.ErrNodeExists {
				return err
			}
		}

		// get the shard, checks a couple things
		si, err := wr.ts.GetShard(tablet.Keyspace, tablet.Shard)
		if err != nil {
			return fmt.Errorf("missing parent shard, use -parent option to create it, or CreateKeyspace / CreateShard")
		}
		if 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 == topo.TYPE_MASTER && !si.MasterAlias.IsZero() && si.MasterAlias != tablet.Alias && !force {
			return fmt.Errorf("creating this tablet would override old master %v in shard %v/%v", si.MasterAlias, tablet.Keyspace, tablet.Shard)
		}

		// see if we specified a parent, otherwise get it from the shard
		if tablet.Parent.IsZero() && tablet.Type.IsSlaveType() {
			if si.MasterAlias.IsZero() {
				return fmt.Errorf("trying to create tablet %v in shard %v/%v without a master", tablet.Alias, tablet.Keyspace, tablet.Shard)
			}
			tablet.Parent = si.MasterAlias
		}

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

	err := topo.CreateTablet(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(tablet.Alias)
			if err != nil {
				log.Warningf("failed reading tablet %v: %v", tablet.Alias, err)
			} else {
				if oldTablet.Keyspace == tablet.Keyspace && oldTablet.Shard == tablet.Shard {
					*(oldTablet.Tablet) = *tablet
					if err := topo.UpdateTablet(wr.ts, oldTablet); err != nil {
						log.Warningf("failed updating tablet %v: %v", tablet.Alias, err)
						// now fall through the Scrap case
					} else {
						if !tablet.IsInReplicationGraph() {
							return nil
						}

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

// 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 *topo.Tablet, force, createShardAndKeyspace, update bool) error {
	if err := tablet.Complete(); err != nil {
		return err
	}

	if tablet.IsInReplicationGraph() {
		// 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.ProtoToKeyRange(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 == topo.TYPE_MASTER && !topo.TabletAliasIsZero(si.MasterAlias) && topo.ProtoToTabletAlias(si.MasterAlias) != tablet.Alias && !force {
			return fmt.Errorf("creating this tablet would override old master %v in shard %v/%v", si.MasterAlias, tablet.Keyspace, tablet.Shard)
		}

		// update the shard record if needed
		if err := wr.updateShardCellsAndMaster(ctx, si, topo.TabletAliasToProto(tablet.Alias), topo.TabletTypeToProto(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", 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", tablet.Alias, err)
						// now fall through the Scrap case
					} else {
						if !tablet.IsInReplicationGraph() {
							return nil
						}

						if err := topo.UpdateTabletReplicationData(ctx, wr.ts, tablet); err != nil {
							wr.Logger().Warningf("failed updating tablet replication data for %v: %v", 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", 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", tablet.Alias, err)
			}
			return topo.CreateTablet(ctx, wr.ts, tablet)
		}
	}
	return err
}

// 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(tablet *topo.Tablet, force, createShardAndKeyspace, update bool) error {
	if err := tablet.Complete(); err != nil {
		return err
	}
	if tablet.Parent.IsZero() && tablet.Type.IsSlaveType() {
		parentAlias, err := wr.getMasterAlias(tablet.Keyspace, tablet.Shard)
		if err != nil {
			return err
		}
		tablet.Parent = parentAlias
	}

	if tablet.IsInReplicationGraph() {
		// create the parent keyspace and shard if needed
		if createShardAndKeyspace {
			if err := wr.ts.CreateKeyspace(tablet.Keyspace); err != nil && err != topo.ErrNodeExists {
				return err
			}

			if err := topo.CreateShard(wr.ts, tablet.Keyspace, tablet.Shard); err != nil && err != topo.ErrNodeExists {
				return err
			}
		}

		// get the shard, checks KeyRange is the same
		si, err := wr.ts.GetShard(tablet.Keyspace, tablet.Shard)
		if err != nil {
			return fmt.Errorf("Missing parent shard, use -parent option to create it, or CreateKeyspace / CreateShard")
		}
		if si.KeyRange != tablet.KeyRange {
			return fmt.Errorf("Shard %v/%v has a different KeyRange: %v != %v", tablet.Keyspace, tablet.Shard, si.KeyRange, tablet.KeyRange)
		}
	}

	err := topo.CreateTablet(wr.ts, tablet)
	if err != nil && err == topo.ErrNodeExists {
		// Try to update nicely, but if it fails fall back to force behavior.
		if update {
			oldTablet, err := wr.ts.GetTablet(tablet.Alias())
			if err != nil {
				relog.Warning("failed reading tablet %v: %v", tablet.Alias(), err)
			} else {
				if oldTablet.Keyspace == tablet.Keyspace && oldTablet.Shard == tablet.Shard {
					*(oldTablet.Tablet) = *tablet
					err := topo.UpdateTablet(wr.ts, oldTablet)
					if err != nil {
						relog.Warning("failed updating tablet %v: %v", tablet.Alias(), err)
					} else {
						return nil
					}
				}
			}
		}
		if force {
			if _, err = wr.Scrap(tablet.Alias(), force, false); err != nil {
				relog.Error("failed scrapping tablet %v: %v", tablet.Alias(), err)
				return err
			}
			if err := wr.ts.DeleteTablet(tablet.Alias()); err != nil {
				// we ignore this
				relog.Error("failed deleting tablet %v: %v", tablet.Alias(), err)
			}
			return topo.CreateTablet(wr.ts, tablet)
		}
	}
	return err
}

// 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(tablet *topo.Tablet, force, createShardAndKeyspace, update bool) error {
	if err := tablet.Complete(); err != nil {
		return err
	}
	if tablet.Parent.IsZero() && tablet.Type.IsSlaveType() {
		parentAlias, err := wr.getMasterAlias(tablet.Keyspace, tablet.Shard)
		if err != nil {
			return err
		}
		tablet.Parent = parentAlias
	}

	if tablet.IsInReplicationGraph() {
		// create the parent keyspace and shard if needed
		if createShardAndKeyspace {
			if err := wr.ts.CreateKeyspace(tablet.Keyspace); err != nil && err != topo.ErrNodeExists {
				return err
			}

			if err := topo.CreateShard(wr.ts, tablet.Keyspace, tablet.Shard); err != nil && err != topo.ErrNodeExists {
				return err
			}
		}

		// get the shard, checks KeyRange is the same
		si, err := wr.ts.GetShard(tablet.Keyspace, tablet.Shard)
		if err != nil {
			return fmt.Errorf("Missing parent shard, use -parent option to create it, or CreateKeyspace / CreateShard")
		}
		if si.KeyRange != tablet.KeyRange {
			return fmt.Errorf("Shard %v/%v has a different KeyRange: %v != %v", tablet.Keyspace, tablet.Shard, si.KeyRange, tablet.KeyRange)
		}

		// add the tablet's cell to the shard cell if needed
		if !si.HasCell(tablet.Cell) {
			actionNode := wr.ai.UpdateShard()
			lockPath, err := wr.lockShard(tablet.Keyspace, tablet.Shard, actionNode)
			if err != nil {
				return err
			}

			// re-read the shard with the lock
			si, err = wr.ts.GetShard(tablet.Keyspace, tablet.Shard)
			if err != nil {
				return wr.unlockShard(tablet.Keyspace, tablet.Shard, actionNode, lockPath, err)
			}

			// update it
			if !si.HasCell(tablet.Cell) {
				si.Cells = append(si.Cells, tablet.Cell)

				// write it back
				if err := wr.ts.UpdateShard(si); err != nil {
					return wr.unlockShard(tablet.Keyspace, tablet.Shard, actionNode, lockPath, err)
				}
			}

			// and unlock
			if err := wr.unlockShard(tablet.Keyspace, tablet.Shard, actionNode, lockPath, err); err != nil {
				return err
			}

			// also create the cell's ShardReplication
			if err := wr.ts.CreateShardReplication(tablet.Cell, tablet.Keyspace, tablet.Shard, &topo.ShardReplication{}); err != nil && err != topo.ErrNodeExists {
				return err
			}
		}
	}

	err := topo.CreateTablet(wr.ts, tablet)
	if err != nil && err == topo.ErrNodeExists {
		// Try to update nicely, but if it fails fall back to force behavior.
		if update {
			oldTablet, err := wr.ts.GetTablet(tablet.Alias())
			if err != nil {
				log.Warningf("failed reading tablet %v: %v", tablet.Alias(), err)
			} else {
				if oldTablet.Keyspace == tablet.Keyspace && oldTablet.Shard == tablet.Shard {
					*(oldTablet.Tablet) = *tablet
					err := topo.UpdateTablet(wr.ts, oldTablet)
					if err != nil {
						log.Warningf("failed updating tablet %v: %v", tablet.Alias(), err)
					} else {
						return nil
					}
				}
			}
		}
		if force {
			if _, err = wr.Scrap(tablet.Alias(), force, false); err != nil {
				log.Errorf("failed scrapping tablet %v: %v", tablet.Alias(), err)
				return err
			}
//.........这里部分代码省略.........

// changeCallback is run after every action that might
// have changed something in the tablet record.
func (agent *ActionAgent) changeCallback(oldTablet, newTablet *topo.Tablet) error {
	allowQuery := newTablet.IsRunningQueryService()

	// Read the shard to get SourceShards / TabletControlMap if
	// we're going to use it.
	var shardInfo *topo.ShardInfo
	var tabletControl *topo.TabletControl
	var blacklistedTables []string
	var err error
	if allowQuery {
		shardInfo, err = agent.TopoServer.GetShard(newTablet.Keyspace, newTablet.Shard)
		if err != nil {
			log.Errorf("Cannot read shard for this tablet %v, might have inaccurate SourceShards and TabletControls: %v", newTablet.Alias, err)
		} else {
			if newTablet.Type == topo.TYPE_MASTER {
				allowQuery = len(shardInfo.SourceShards) == 0
			}
			if tc, ok := shardInfo.TabletControlMap[newTablet.Type]; ok {
				if topo.InCellList(newTablet.Alias.Cell, tc.Cells) {
					if tc.DisableQueryService {
						allowQuery = false
					}
					blacklistedTables = tc.BlacklistedTables
					tabletControl = tc
				}
			}
		}
	}

	// Read the keyspace on masters to get ShardingColumnType,
	// for binlog replication, only if source shards are set.
	var keyspaceInfo *topo.KeyspaceInfo
	if newTablet.Type == topo.TYPE_MASTER && shardInfo != nil && len(shardInfo.SourceShards) > 0 {
		keyspaceInfo, err = agent.TopoServer.GetKeyspace(newTablet.Keyspace)
		if err != nil {
			log.Errorf("Cannot read keyspace for this tablet %v: %v", newTablet.Alias, err)
			keyspaceInfo = nil
		}
	}

	if allowQuery {
		// There are a few transitions when we're
		// going to need to restart the query service:
		// - transitioning from replica to master, so clients
		//   that were already connected don't keep on using
		//   the master as replica or rdonly.
		// - having different parameters for the query
		//   service. It needs to stop and restart with the
		//   new parameters. That includes:
		//   - changing KeyRange
		//   - changing the BlacklistedTables list
		if (newTablet.Type == topo.TYPE_MASTER &&
			oldTablet.Type != topo.TYPE_MASTER) ||
			(newTablet.KeyRange != oldTablet.KeyRange) ||
			!reflect.DeepEqual(blacklistedTables, agent.BlacklistedTables()) {
			agent.disallowQueries()
		}
		if err := agent.allowQueries(newTablet, blacklistedTables); err != nil {
			log.Errorf("Cannot start query service: %v", err)
		}
	} else {
		agent.disallowQueries()
	}

	// save the tabletControl we've been using, so the background
	// healthcheck makes the same decisions as we've been making.
	agent.setTabletControl(tabletControl)

	// update stream needs to be started or stopped too
	if agent.DBConfigs != nil {
		if topo.IsRunningUpdateStream(newTablet.Type) {
			binlog.EnableUpdateStreamService(agent.DBConfigs.App.DbName, agent.Mysqld)
		} else {
			binlog.DisableUpdateStreamService()
		}
	}

	statsType.Set(string(newTablet.Type))
	statsKeyspace.Set(newTablet.Keyspace)
	statsShard.Set(newTablet.Shard)
	statsKeyRangeStart.Set(string(newTablet.KeyRange.Start.Hex()))
	statsKeyRangeEnd.Set(string(newTablet.KeyRange.End.Hex()))

	// See if we need to start or stop any binlog player
	if agent.BinlogPlayerMap != nil {
		if newTablet.Type == topo.TYPE_MASTER {
			agent.BinlogPlayerMap.RefreshMap(newTablet, keyspaceInfo, shardInfo)
		} else {
			agent.BinlogPlayerMap.StopAllPlayersAndReset()
		}
	}
	return nil
}