func repoNewDataHandler(c web.C, w http.ResponseWriter, r *http.Request) {
	uuid := c.Env["uuid"].(dvid.UUID)
	config := dvid.NewConfig()
	if err := config.SetByJSON(r.Body); err != nil {
		BadRequest(w, r, fmt.Sprintf("Error decoding POSTed JSON config for 'new': %v", err))
		return
	}

	// Make sure that the passed configuration has data type and instance name.
	typename, found, err := config.GetString("typename")
	if !found || err != nil {
		BadRequest(w, r, "POST on repo endpoint requires specification of valid 'typename'")
		return
	}
	dataname, found, err := config.GetString("dataname")
	if !found || err != nil {
		BadRequest(w, r, "POST on repo endpoint requires specification of valid 'dataname'")
		return
	}
	typeservice, err := datastore.TypeServiceByName(dvid.TypeString(typename))
	if err != nil {
		BadRequest(w, r, err)
		return
	}
	_, err = datastore.NewData(uuid, typeservice, dvid.InstanceName(dataname), config)
	if err != nil {
		BadRequest(w, r, err)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	fmt.Fprintf(w, "{%q: 'Added %s [%s] to node %s'}", "result", dataname, typename, uuid)
}

// Sets package-level testRepo and TestVersionID
func initTestRepo() (dvid.UUID, dvid.VersionID) {
	testMu.Lock()
	defer testMu.Unlock()
	if mstype == nil {
		var err error
		mstype, err = datastore.TypeServiceByName(TypeName)
		if err != nil {
			log.Fatalf("Can't get imagetile type: %s\n", err)
		}
		grayscaleT, err = datastore.TypeServiceByName("uint8blk")
		if err != nil {
			log.Fatalf("Can't get grayscale type: %s\n", err)
		}
	}
	return datastore.NewTestRepo()
}

// Sets package-level testRepo and TestVersionID
func initTestRepo() (dvid.UUID, dvid.VersionID) {
	testMu.Lock()
	defer testMu.Unlock()
	if labelsT == nil {
		var err error
		labelsT, err = datastore.TypeServiceByName("labelblk")
		if err != nil {
			log.Fatalf("Can't get labelblk type: %s\n", err)
		}
		rgbaT, err = datastore.TypeServiceByName("rgba8blk")
		if err != nil {
			log.Fatalf("Can't get rgba8blk type: %s\n", err)
		}
	}
	return tests.NewRepo()
}

func typehelpHandler(c web.C, w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain")
	typename := dvid.TypeString(c.URLParams["typename"])
	typeservice, err := datastore.TypeServiceByName(typename)
	if err != nil {
		BadRequest(w, r, err)
		return
	}
	fmt.Fprintf(w, typeservice.Help())
}

// Sets package-level testRepo and TestVersionID
func initTestRepo() (dvid.UUID, dvid.VersionID) {
	if dtype == nil {
		var err error
		dtype, err = datastore.TypeServiceByName(TypeName)
		if err != nil {
			log.Fatalf("Can't get labelgraph type: %v\n", err)
		}
	}
	return datastore.NewTestRepo()
}

// Sets package-level testRepo and TestVersionID
func initTestRepo() (dvid.UUID, dvid.VersionID) {
	testMu.Lock()
	defer testMu.Unlock()
	if grayscaleT == nil {
		var err error
		grayscaleT, err = datastore.TypeServiceByName("uint8blk")
		if err != nil {
			log.Fatalf("Can't get uint8blk type: %s\n", err)
		}
		rgbaT, err = datastore.TypeServiceByName("rgba8blk")
		if err != nil {
			log.Fatalf("Can't get rgba8blk type: %s\n", err)
		}
		roiT, err = datastore.TypeServiceByName("roi")
		if err != nil {
			log.Fatalf("Can't get ROI type: %s\n", err)
		}
	}
	return datastore.NewTestRepo()
}

// Sets package-level testRepo and TestVersionID
func initTestRepo() (dvid.UUID, dvid.VersionID) {
	testMu.Lock()
	defer testMu.Unlock()
	if roitype == nil {
		var err error
		roitype, err = datastore.TypeServiceByName(TypeName)
		if err != nil {
			log.Fatalf("Can't get ROI type: %v\n", err)
		}
	}
	return datastore.NewTestRepo()
}

// Sets package-level testRepo and TestVersionID
func initTestRepo() (dvid.UUID, dvid.VersionID) {
	testMu.Lock()
	defer testMu.Unlock()
	if dtype == nil {
		var err error
		dtype, err = datastore.TypeServiceByName(TypeName)
		if err != nil {
			log.Fatalf("Can't get multichan16 type: %v\n", err)
		}
	}
	return tests.NewRepo()
}

// ForegroundROI creates a new ROI by determining all non-background blocks.
func (d *Data) ForegroundROI(req datastore.Request, reply *datastore.Response) error {
	if d.Values.BytesPerElement() != 1 {
		return fmt.Errorf("Foreground ROI command only implemented for 1 byte/voxel data!")
	}

	// Parse the request
	var uuidStr, dataName, cmdStr, destName, backgroundStr string
	req.CommandArgs(1, &uuidStr, &dataName, &cmdStr, &destName, &backgroundStr)

	// Get the version and repo
	uuid, versionID, err := datastore.MatchingUUID(uuidStr)
	if err != nil {
		return err
	}
	if err = datastore.AddToNodeLog(uuid, []string{req.Command.String()}); err != nil {
		return err
	}

	// Use existing destination data or a new ROI data.
	var dest *roi.Data
	dest, err = roi.GetByUUID(uuid, dvid.InstanceName(destName))
	if err != nil {
		config := dvid.NewConfig()
		typeservice, err := datastore.TypeServiceByName("roi")
		if err != nil {
			return err
		}
		dataservice, err := datastore.NewData(uuid, typeservice, dvid.InstanceName(destName), config)
		if err != nil {
			return err
		}
		var ok bool
		dest, ok = dataservice.(*roi.Data)
		if !ok {
			return fmt.Errorf("Could not create ROI data instance")
		}
	}

	// Asynchronously process the voxels.
	background, err := dvid.StringToPointNd(backgroundStr, ",")
	if err != nil {
		return err
	}
	go d.foregroundROI(versionID, dest, background)

	return nil
}

// CreateComposite creates a new rgba8 image by combining hash of labels + the grayscale
func (d *Data) CreateComposite(request datastore.Request, reply *datastore.Response) error {
	timedLog := dvid.NewTimeLog()

	// Parse the request
	var uuidStr, dataName, cmdStr, grayscaleName, destName string
	request.CommandArgs(1, &uuidStr, &dataName, &cmdStr, &grayscaleName, &destName)

	// Get the version
	uuid, v, err := datastore.MatchingUUID(uuidStr)
	if err != nil {
		return err
	}

	// Log request
	if err = datastore.AddToNodeLog(uuid, []string{request.Command.String()}); err != nil {
		return err
	}

	// Get the grayscale data.
	dataservice, err := datastore.GetDataByUUIDName(uuid, dvid.InstanceName(grayscaleName))
	if err != nil {
		return err
	}
	grayscale, ok := dataservice.(*imageblk.Data)
	if !ok {
		return fmt.Errorf("%s is not the name of uint8 data", grayscaleName)
	}

	// Create a new rgba8blk data.
	var compservice datastore.DataService
	compservice, err = datastore.GetDataByUUIDName(uuid, dvid.InstanceName(destName))
	if err == nil {
		return fmt.Errorf("Data instance with name %q already exists", destName)
	}
	typeService, err := datastore.TypeServiceByName("rgba8blk")
	if err != nil {
		return fmt.Errorf("Could not get rgba8 type service from DVID")
	}
	config := dvid.NewConfig()
	compservice, err = datastore.NewData(uuid, typeService, dvid.InstanceName(destName), config)
	if err != nil {
		return err
	}
	composite, ok := compservice.(*imageblk.Data)
	if !ok {
		return fmt.Errorf("Error: %s was unable to be set to rgba8 data", destName)
	}

	// Iterate through all labels and grayscale chunks incrementally in Z, a layer at a time.
	wg := new(sync.WaitGroup)
	op := &compositeOp{grayscale, composite, v}
	chunkOp := &storage.ChunkOp{op, wg}

	store, err := d.GetOrderedKeyValueDB()
	if err != nil {
		return err
	}
	ctx := datastore.NewVersionedCtx(d, v)
	extents := d.Extents()
	blockBeg := imageblk.NewTKey(extents.MinIndex)
	blockEnd := imageblk.NewTKey(extents.MaxIndex)
	err = store.ProcessRange(ctx, blockBeg, blockEnd, chunkOp, storage.ChunkFunc(d.CreateCompositeChunk))
	wg.Wait()

	// Set new mapped data to same extents.
	composite.Properties.Extents = grayscale.Properties.Extents
	if err := datastore.SaveDataByUUID(uuid, composite); err != nil {
		dvid.Infof("Could not save new data '%s': %v\n", destName, err)
	}

	timedLog.Infof("Created composite of %s and %s", grayscaleName, destName)
	return nil
}

// Do acts as a switchboard for remote command execution
func (c *RPCConnection) Do(cmd datastore.Request, reply *datastore.Response) error {
	if reply == nil {
		dvid.Debugf("reply is nil coming in!\n")
		return nil
	}
	if cmd.Name() == "" {
		return fmt.Errorf("Server error: got empty command!")
	}

	switch cmd.Name() {

	case "help":
		reply.Text = fmt.Sprintf(RPCHelpMessage, config.RPCAddress(), config.HTTPAddress())

	case "shutdown":
		Shutdown()
		// Make this process shutdown in a second to allow time for RPC to finish.
		// TODO -- Better way to do this?
		log.Printf("DVID server halted due to 'shutdown' command.")
		reply.Text = fmt.Sprintf("DVID server at %s has been halted.\n", config.RPCAddress())
		go func() {
			time.Sleep(1 * time.Second)
			os.Exit(0)
		}()

	case "types":
		if len(cmd.Command) == 1 {
			text := "\nData Types within this DVID Server\n"
			text += "----------------------------------\n"
			mapTypes, err := datastore.Types()
			if err != nil {
				return fmt.Errorf("Error trying to retrieve data types within this DVID server!")
			}
			for url, typeservice := range mapTypes {
				text += fmt.Sprintf("%-20s %s\n", typeservice.GetTypeName(), url)
			}
			reply.Text = text
		} else {
			if len(cmd.Command) != 3 || cmd.Command[2] != "help" {
				return fmt.Errorf("Unknown types command: %q", cmd.Command)
			}
			var typename string
			cmd.CommandArgs(1, &typename)
			typeservice, err := datastore.TypeServiceByName(dvid.TypeString(typename))
			if err != nil {
				return err
			}
			reply.Text = typeservice.Help()
		}

	case "repos":
		var subcommand, alias, description, uuidStr string
		cmd.CommandArgs(1, &subcommand, &alias, &description, &uuidStr)
		switch subcommand {
		case "new":
			var assign *dvid.UUID
			if uuidStr == "" {
				assign = nil
			} else {
				u := dvid.UUID(uuidStr)
				assign = &u
			}
			root, err := datastore.NewRepo(alias, description, assign)
			if err != nil {
				return err
			}
			if err := datastore.SetRepoAlias(root, alias); err != nil {
				return err
			}
			if err := datastore.SetRepoDescription(root, description); err != nil {
				return err
			}
			reply.Text = fmt.Sprintf("New repo %q created with head node %s\n", alias, root)
		default:
			return fmt.Errorf("Unknown repos command: %q", subcommand)
		}

	case "repo":
		var uuidStr, subcommand string
		cmd.CommandArgs(1, &uuidStr, &subcommand)
		uuid, _, err := datastore.MatchingUUID(uuidStr)
		if err != nil {
			return err
		}

		switch subcommand {
		case "new":
			var typename, dataname string
			cmd.CommandArgs(3, &typename, &dataname)

			// Get TypeService
			typeservice, err := datastore.TypeServiceByName(dvid.TypeString(typename))
			if err != nil {
				return err
			}

			// Create new data
			config := cmd.Settings()
			_, err = datastore.NewData(uuid, typeservice, dvid.InstanceName(dataname), config)
//.........这里部分代码省略.........

// switchboard for remote command execution
func handleCommand(cmd *datastore.Request) (reply *datastore.Response, err error) {
	if cmd.Name() == "" {
		err = fmt.Errorf("Server error: got empty command!")
		return
	}
	reply = new(datastore.Response)

	switch cmd.Name() {

	case "help":
		reply.Text = fmt.Sprintf(RPCHelpMessage, config.RPCAddress(), config.HTTPAddress())

	case "shutdown":
		dvid.Infof("DVID server halting due to 'shutdown' command.")
		reply.Text = fmt.Sprintf("DVID server at %s is being shutdown...\n", config.RPCAddress())
		// launch goroutine shutdown so we can concurrently return shutdown message to client.
		go Shutdown()

	case "types":
		if len(cmd.Command) == 1 {
			text := "\nData Types within this DVID Server\n"
			text += "----------------------------------\n"
			var mapTypes map[dvid.URLString]datastore.TypeService
			if mapTypes, err = datastore.Types(); err != nil {
				err = fmt.Errorf("Error trying to retrieve data types within this DVID server!")
				return
			}
			for url, typeservice := range mapTypes {
				text += fmt.Sprintf("%-20s %s\n", typeservice.GetTypeName(), url)
			}
			reply.Text = text
		} else {
			if len(cmd.Command) != 3 || cmd.Command[2] != "help" {
				err = fmt.Errorf("Unknown types command: %q", cmd.Command)
				return
			}
			var typename string
			var typeservice datastore.TypeService
			cmd.CommandArgs(1, &typename)
			if typeservice, err = datastore.TypeServiceByName(dvid.TypeString(typename)); err != nil {
				return
			}
			reply.Text = typeservice.Help()
		}

	case "repos":
		var subcommand string
		cmd.CommandArgs(1, &subcommand)

		switch subcommand {
		case "new":
			var alias, description string
			cmd.CommandArgs(2, &alias, &description)

			config := cmd.Settings()
			var uuidStr, passcode string
			var found bool
			if uuidStr, found, err = config.GetString("uuid"); err != nil {
				return
			}
			var assign *dvid.UUID
			if !found {
				assign = nil
			} else {
				uuid := dvid.UUID(uuidStr)
				assign = &uuid
			}
			if passcode, found, err = config.GetString("passcode"); err != nil {
				return
			}
			var root dvid.UUID
			root, err = datastore.NewRepo(alias, description, assign, passcode)
			if err != nil {
				return
			}
			if err = datastore.SetRepoAlias(root, alias); err != nil {
				return
			}
			if err = datastore.SetRepoDescription(root, description); err != nil {
				return
			}
			reply.Text = fmt.Sprintf("New repo %q created with head node %s\n", alias, root)

		case "delete":
			var uuidStr, passcode string
			cmd.CommandArgs(2, &uuidStr, &passcode)

			var uuid dvid.UUID
			if uuid, _, err = datastore.MatchingUUID(uuidStr); err != nil {
				return
			}
			if err = datastore.DeleteRepo(uuid, passcode); err != nil {
				return
			}
			reply.Text = fmt.Sprintf("Started deletion of repo %s.\n", uuid)

		default:
			err = fmt.Errorf("Unknown repos command: %q", subcommand)
			return
//.........这里部分代码省略.........