// DeleteTablet removes a tablet from a shard.
// - if allowMaster is set, we can Delete a master tablet (and clear
// its record from the Shard record if it was the master).
// - if skipRebuild is set, we do not rebuild the serving graph.
func (wr *Wrangler) DeleteTablet(ctx context.Context, tabletAlias *topodatapb.TabletAlias, allowMaster, skipRebuild bool) error {
	// load the tablet, see if we'll need to rebuild
	ti, err := wr.ts.GetTablet(ctx, tabletAlias)
	if err != nil {
		return err
	}
	rebuildRequired := ti.IsInServingGraph()
	wasMaster := ti.Type == topodatapb.TabletType_MASTER
	if wasMaster && !allowMaster {
		return fmt.Errorf("cannot delete tablet %v as it is a master, use allow_master flag", topoproto.TabletAliasString(tabletAlias))
	}

	// remove the record and its replication graph entry
	if err := topotools.DeleteTablet(ctx, wr.ts, ti.Tablet); err != nil {
		return err
	}

	// update the Shard object if the master was scrapped.
	// we lock the shard to not conflict with reparent operations.
	if wasMaster {
		actionNode := actionnode.UpdateShard()
		lockPath, err := wr.lockShard(ctx, ti.Keyspace, ti.Shard, actionNode)
		if err != nil {
			return err
		}

		// update the shard record's master
		if _, err := wr.ts.UpdateShardFields(ctx, ti.Keyspace, ti.Shard, func(s *topodatapb.Shard) error {
			if !topoproto.TabletAliasEqual(s.MasterAlias, tabletAlias) {
				wr.Logger().Warningf("Deleting master %v from shard %v/%v but master in Shard object was %v", topoproto.TabletAliasString(tabletAlias), ti.Keyspace, ti.Shard, topoproto.TabletAliasString(s.MasterAlias))
				return topo.ErrNoUpdateNeeded
			}
			s.MasterAlias = nil
			return nil
		}); err != nil {
			return wr.unlockShard(ctx, ti.Keyspace, ti.Shard, actionNode, lockPath, err)
		}

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

	// and rebuild the original shard if needed
	if !rebuildRequired {
		wr.Logger().Infof("Rebuild not required")
		return nil
	}
	if skipRebuild {
		wr.Logger().Warningf("Rebuild required, but skipping it")
		return nil
	}
	_, err = wr.RebuildShardGraph(ctx, ti.Keyspace, ti.Shard, []string{ti.Alias.Cell})
	return err
}

// SourceShardAdd will add a new SourceShard inside a shard
func (wr *Wrangler) SourceShardAdd(ctx context.Context, keyspace, shard string, uid uint32, skeyspace, sshard string, keyRange key.KeyRange, tables []string) error {
	actionNode := actionnode.UpdateShard()
	lockPath, err := wr.lockShard(ctx, keyspace, shard, actionNode)
	if err != nil {
		return err
	}

	err = wr.sourceShardAdd(ctx, keyspace, shard, uid, skeyspace, sshard, keyRange, tables)
	return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, err)
}

// SourceShardDelete will delete a SourceShard inside a shard, by index.
func (wr *Wrangler) SourceShardDelete(ctx context.Context, keyspace, shard string, uid uint32) error {
	actionNode := actionnode.UpdateShard()
	lockPath, err := wr.lockShard(ctx, keyspace, shard, actionNode)
	if err != nil {
		return err
	}

	err = wr.sourceShardDelete(ctx, keyspace, shard, uid)
	return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, err)
}

// RemoveShardCell will remove a cell from the Cells list in a shard.
//
// It will first check the shard has no tablets there. If 'force' is
// specified, it will remove the cell even when the tablet map cannot
// be retrieved. This is intended to be used when a cell is completely
// down and its topology server cannot even be reached.
//
// If 'recursive' is specified, it will delete any tablets in the cell/shard,
// with the assumption that the tablet processes have already been terminated.
func (wr *Wrangler) RemoveShardCell(ctx context.Context, keyspace, shard, cell string, force, recursive bool) error {
	actionNode := actionnode.UpdateShard()
	lockPath, err := wr.lockShard(ctx, keyspace, shard, actionNode)
	if err != nil {
		return err
	}

	err = wr.removeShardCell(ctx, keyspace, shard, cell, force, recursive)
	return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, err)
}

// SetShardBlacklistedTables changes the BlacklistedTablesMap
// parameter of a shard.  It does not rebuild any serving graph or do
// any consistency check.
func (wr *Wrangler) SetShardBlacklistedTables(keyspace, shard string, tabletType topo.TabletType, tables []string) error {

	actionNode := actionnode.UpdateShard()
	lockPath, err := wr.lockShard(keyspace, shard, actionNode)
	if err != nil {
		return err
	}

	err = wr.setShardBlacklistedTables(keyspace, shard, tabletType, tables)
	return wr.unlockShard(keyspace, shard, actionNode, lockPath, err)
}

// updateShardCellsAndMaster will update the 'Cells' and possibly
// MasterAlias records for the shard, if needed.
func (wr *Wrangler) updateShardCellsAndMaster(ctx context.Context, si *topo.ShardInfo, tabletAlias topo.TabletAlias, tabletType topo.TabletType, force bool) error {
	// See if we need to update the Shard:
	// - add the tablet's cell to the shard's Cells if needed
	// - change the master if needed
	shardUpdateRequired := false
	if !si.HasCell(tabletAlias.Cell) {
		shardUpdateRequired = true
	}
	if tabletType == topo.TYPE_MASTER && si.MasterAlias != tabletAlias {
		shardUpdateRequired = true
	}
	if !shardUpdateRequired {
		return nil
	}

	actionNode := actionnode.UpdateShard()
	keyspace := si.Keyspace()
	shard := si.ShardName()
	lockPath, err := wr.lockShard(ctx, keyspace, shard, actionNode)
	if err != nil {
		return err
	}

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

	// update it
	wasUpdated := false
	if !si.HasCell(tabletAlias.Cell) {
		si.Cells = append(si.Cells, tabletAlias.Cell)
		wasUpdated = true
	}
	if tabletType == topo.TYPE_MASTER && si.MasterAlias != tabletAlias {
		if !si.MasterAlias.IsZero() && !force {
			return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, fmt.Errorf("creating this tablet would override old master %v in shard %v/%v", si.MasterAlias, keyspace, shard))
		}
		si.MasterAlias = tabletAlias
		wasUpdated = true
	}

	if wasUpdated {
		// write it back
		if err := topo.UpdateShard(ctx, wr.ts, si); err != nil {
			return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, err)
		}
	}

	// and unlock
	return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, err)
}

// SetShardTabletControl changes the TabletControl records
// for a shard.  It does not rebuild any serving graph or do
// cross-shard consistency check.
// - if disableQueryService is set, tables has to be empty
// - if disableQueryService is not set, and tables is empty, we remove
//   the TabletControl record for the cells
func (wr *Wrangler) SetShardTabletControl(ctx context.Context, keyspace, shard string, tabletType topo.TabletType, cells []string, remove, disableQueryService bool, tables []string) error {

	if disableQueryService && len(tables) > 0 {
		return fmt.Errorf("SetShardTabletControl cannot have both DisableQueryService set and tables set")
	}

	actionNode := actionnode.UpdateShard()
	lockPath, err := wr.lockShard(ctx, keyspace, shard, actionNode)
	if err != nil {
		return err
	}

	err = wr.setShardTabletControl(ctx, keyspace, shard, tabletType, cells, remove, disableQueryService, tables)
	return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, err)
}

// updateShardCellsAndMaster will update the 'Cells' and possibly
// MasterAlias records for the shard, if needed.
func (wr *Wrangler) updateShardCellsAndMaster(ctx context.Context, si *topo.ShardInfo, tabletAlias *topodatapb.TabletAlias, tabletType topodatapb.TabletType, allowMasterOverride bool) error {
	// See if we need to update the Shard:
	// - add the tablet's cell to the shard's Cells if needed
	// - change the master if needed
	shardUpdateRequired := false
	if !si.HasCell(tabletAlias.Cell) {
		shardUpdateRequired = true
	}
	if tabletType == topodatapb.TabletType_MASTER && !topoproto.TabletAliasEqual(si.MasterAlias, tabletAlias) {
		shardUpdateRequired = true
	}
	if !shardUpdateRequired {
		return nil
	}

	// we do need to update the shard, lock it to not interfere with
	// reparenting operations.
	actionNode := actionnode.UpdateShard()
	keyspace := si.Keyspace()
	shard := si.ShardName()
	lockPath, err := wr.lockShard(ctx, keyspace, shard, actionNode)
	if err != nil {
		return err
	}

	// run the update
	_, err = wr.ts.UpdateShardFields(ctx, keyspace, shard, func(s *topodatapb.Shard) error {
		wasUpdated := false
		if !topoproto.ShardHasCell(s, tabletAlias.Cell) {
			s.Cells = append(s.Cells, tabletAlias.Cell)
			wasUpdated = true
		}

		if tabletType == topodatapb.TabletType_MASTER && !topoproto.TabletAliasEqual(s.MasterAlias, tabletAlias) {
			if !topoproto.TabletAliasIsZero(s.MasterAlias) && !allowMasterOverride {
				return fmt.Errorf("creating this tablet would override old master %v in shard %v/%v", topoproto.TabletAliasString(s.MasterAlias), keyspace, shard)
			}
			s.MasterAlias = tabletAlias
			wasUpdated = true
		}

		if !wasUpdated {
			return topo.ErrNoUpdateNeeded
		}
		return nil
	})
	return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, err)
}

// InitTablet initializes the tablet record if necessary.
func (agent *ActionAgent) InitTablet(port, gRPCPort int32) error {
	// only enabled if one of init_tablet_type (when healthcheck
	// is disabled) or init_keyspace (when healthcheck is enabled)
	// is passed in, then check other parameters
	if *initTabletType == "" && *initKeyspace == "" {
		return nil
	}

	// figure out our default target type
	var tabletType topodatapb.TabletType
	if *initTabletType != "" {
		if *targetTabletType != "" {
			log.Fatalf("cannot specify both target_tablet_type and init_tablet_type parameters (as they might conflict)")
		}

		// use the type specified on the command line
		var err error
		tabletType, err = topoproto.ParseTabletType(*initTabletType)
		if err != nil {
			log.Fatalf("Invalid init tablet type %v: %v", *initTabletType, err)
		}

		if tabletType == topodatapb.TabletType_MASTER {
			// We disallow MASTER, so we don't have to change
			// shard.MasterAlias, and deal with the corner cases.
			log.Fatalf("init_tablet_type cannot be %v", tabletType)
		}

	} else if *targetTabletType != "" {
		if strings.ToUpper(*targetTabletType) == topodatapb.TabletType_name[int32(topodatapb.TabletType_MASTER)] {
			log.Fatalf("target_tablet_type cannot be '%v'. Use '%v' instead.", tabletType, topodatapb.TabletType_REPLICA)
		}

		// use spare, the healthcheck will turn us into what
		// we need to be eventually
		tabletType = topodatapb.TabletType_SPARE

	} else {
		log.Fatalf("if init tablet is enabled, one of init_tablet_type or target_tablet_type needs to be specified")
	}

	// create a context for this whole operation
	ctx, cancel := context.WithTimeout(agent.batchCtx, *initTimeout)
	defer cancel()

	// since we're assigned to a shard, make sure it exists, see if
	// we are its master, and update its cells list if necessary
	if *initKeyspace == "" || *initShard == "" {
		log.Fatalf("if init tablet is enabled and the target type is not idle, init_keyspace and init_shard also need to be specified")
	}
	shard, _, err := topo.ValidateShardName(*initShard)
	if err != nil {
		log.Fatalf("cannot validate shard name: %v", err)
	}

	log.Infof("Reading shard record %v/%v", *initKeyspace, shard)

	// read the shard, create it if necessary
	si, err := topotools.GetOrCreateShard(ctx, agent.TopoServer, *initKeyspace, shard)
	if err != nil {
		return fmt.Errorf("InitTablet cannot GetOrCreateShard shard: %v", err)
	}
	if si.MasterAlias != nil && topoproto.TabletAliasEqual(si.MasterAlias, agent.TabletAlias) {
		// we are the current master for this shard (probably
		// means the master tablet process was just restarted),
		// so InitTablet as master.
		tabletType = topodatapb.TabletType_MASTER
	}

	// See if we need to add the tablet's cell to the shard's cell
	// list.  If we do, it has to be under the shard lock.
	if !si.HasCell(agent.TabletAlias.Cell) {
		actionNode := actionnode.UpdateShard()
		lockPath, err := actionNode.LockShard(ctx, agent.TopoServer, *initKeyspace, shard)
		if err != nil {
			return fmt.Errorf("LockShard(%v/%v) failed: %v", *initKeyspace, shard, err)
		}

		// re-read the shard with the lock
		si, err = agent.TopoServer.GetShard(ctx, *initKeyspace, shard)
		if err != nil {
			return actionNode.UnlockShard(ctx, agent.TopoServer, *initKeyspace, shard, lockPath, err)
		}

		// see if we really need to update it now
		if !si.HasCell(agent.TabletAlias.Cell) {
			si.Cells = append(si.Cells, agent.TabletAlias.Cell)

			// write it back
			if err := agent.TopoServer.UpdateShard(ctx, si); err != nil {
				return actionNode.UnlockShard(ctx, agent.TopoServer, *initKeyspace, shard, lockPath, err)
			}
		}

		// and unlock
		if err := actionNode.UnlockShard(ctx, agent.TopoServer, *initKeyspace, shard, lockPath, nil); err != nil {
			return err
		}
	}
//.........这里部分代码省略.........

// Scrap a tablet. If force is used, we write to topo.Server
// directly and don't remote-execute the command.
//
// If we scrap the master for a shard, we will clear its record
// from the Shard object (only if that was the right master)
func (wr *Wrangler) Scrap(ctx context.Context, tabletAlias topo.TabletAlias, force, skipRebuild bool) error {
	// load the tablet, see if we'll need to rebuild
	ti, err := wr.ts.GetTablet(ctx, tabletAlias)
	if err != nil {
		return err
	}
	rebuildRequired := ti.IsInServingGraph()
	wasMaster := ti.Type == topo.TYPE_MASTER

	if force {
		err = topotools.Scrap(ctx, wr.ts, ti.Alias, force)
	} else {
		err = wr.tmc.Scrap(ctx, ti)
	}
	if err != nil {
		return err
	}

	if !rebuildRequired {
		wr.Logger().Infof("Rebuild not required")
		return nil
	}
	if skipRebuild {
		wr.Logger().Warningf("Rebuild required, but skipping it")
		return nil
	}

	// update the Shard object if the master was scrapped
	if wasMaster {
		actionNode := actionnode.UpdateShard()
		lockPath, err := wr.lockShard(ctx, ti.Keyspace, ti.Shard, actionNode)
		if err != nil {
			return err
		}

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

		// update it if the right alias is there
		if topo.TabletAliasEqual(si.MasterAlias, topo.TabletAliasToProto(tabletAlias)) {
			si.MasterAlias = nil

			// write it back
			if err := topo.UpdateShard(ctx, wr.ts, si); err != nil {
				return wr.unlockShard(ctx, ti.Keyspace, ti.Shard, actionNode, lockPath, err)
			}
		} else {
			wr.Logger().Warningf("Scrapping master %v from shard %v/%v but master in Shard object was %v", tabletAlias, ti.Keyspace, ti.Shard, si.MasterAlias)
		}

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

	// and rebuild the original shard
	_, err = wr.RebuildShardGraph(ctx, ti.Keyspace, ti.Shard, []string{ti.Alias.Cell})
	return err
}

// Scrap a tablet. If force is used, we write to topo.Server
// directly and don't remote-execute the command.
//
// If we scrap the master for a shard, we will clear its record
// from the Shard object (only if that was the right master)
func (wr *Wrangler) Scrap(tabletAlias topo.TabletAlias, force, skipRebuild bool) (actionPath string, err error) {
	// load the tablet, see if we'll need to rebuild
	ti, err := wr.ts.GetTablet(tabletAlias)
	if err != nil {
		return "", err
	}
	rebuildRequired := ti.Tablet.IsInServingGraph()
	wasMaster := ti.Type == topo.TYPE_MASTER

	if force {
		err = topotools.Scrap(wr.ts, ti.Alias, force)
	} else {
		actionPath, err = wr.ai.Scrap(ti.Alias)
	}
	if err != nil {
		return "", err
	}

	if !rebuildRequired {
		log.Infof("Rebuild not required")
		return
	}
	if skipRebuild {
		log.Warningf("Rebuild required, but skipping it")
		return
	}

	// wait for the remote Scrap if necessary
	if actionPath != "" {
		err = wr.WaitForCompletion(actionPath)
		if err != nil {
			return "", err
		}
	}

	// update the Shard object if the master was scrapped
	if wasMaster {
		actionNode := actionnode.UpdateShard()
		lockPath, err := wr.lockShard(ti.Keyspace, ti.Shard, actionNode)
		if err != nil {
			return "", err
		}

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

		// update it if the right alias is there
		if si.MasterAlias == tabletAlias {
			si.MasterAlias = topo.TabletAlias{}

			// write it back
			if err := topo.UpdateShard(wr.ts, si); err != nil {
				return "", wr.unlockShard(ti.Keyspace, ti.Shard, actionNode, lockPath, err)
			}
		} else {
			log.Warningf("Scrapping master %v from shard %v/%v but master in Shard object was %v", tabletAlias, ti.Keyspace, ti.Shard, si.MasterAlias)
		}

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

	// and rebuild the original shard / keyspace
	return "", wr.RebuildShardGraph(ti.Keyspace, ti.Shard, []string{ti.Alias.Cell})
}

// 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
		}

		// See if we need to update the Shard:
		// - add the tablet's cell to the shard's Cells if needed
		// - change the master if needed
		shardUpdateRequired := false
		if !si.HasCell(tablet.Alias.Cell) {
			shardUpdateRequired = true
		}
		if tablet.Type == topo.TYPE_MASTER && si.MasterAlias != tablet.Alias {
			shardUpdateRequired = true
		}

		if shardUpdateRequired {
			actionNode := actionnode.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
			wasUpdated := false
			if !si.HasCell(tablet.Alias.Cell) {
				si.Cells = append(si.Cells, tablet.Alias.Cell)
				wasUpdated = true
			}
			if tablet.Type == topo.TYPE_MASTER && si.MasterAlias != tablet.Alias {
				if !si.MasterAlias.IsZero() && !force {
					return wr.unlockShard(tablet.Keyspace, tablet.Shard, actionNode, lockPath, fmt.Errorf("creating this tablet would override old master %v in shard %v/%v", si.MasterAlias, tablet.Keyspace, tablet.Shard))
				}
				si.MasterAlias = tablet.Alias
				wasUpdated = true
			}

			if wasUpdated {
				// 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.Alias.Cell, tablet.Keyspace, tablet.Shard, &topo.ShardReplication{}); err != nil && err != topo.ErrNodeExists {
				return err
			}
		}
	}
//.........这里部分代码省略.........