Creating an application from a template

 
$ tt create TEMPLATE_NAME [OPTION ...]

tt create creates a new Tarantool application from a template.

Application templates speed up the development of Tarantool applications by defining their initial structure and content. A template can include application code, configuration, build scripts, and other resources.

tt comes with built-in templates for popular use cases. You can also create custom templates for specific purposes.

There are the following built-in templates:

• vshard_cluster: a sharded cluster application for Tarantool 3.0 or later.

• single_instance: a single-instance application for Tarantool 3.0 or later.

• cartridge: a Cartridge cluster application for Tarantool 2.x.

To create the app1 application in the current tt environment from the built-in vshard_cluster template:

 
$ tt create vshard_cluster --name app1 -dst /opt/tt/apps/

The command requests cluster topology parameters, such as the number of shards or routers, interactively during the execution.

To create the application in the /opt/tt/apps directory with default cluster topology and force rewrite the application directory if it already exists:

 
$ tt create vshard_cluster --name app1 -f --non-interactive -dst /opt/tt/apps/

tt searches for custom templates in the directories specified in the templates section of its configuration file.

To create the application app1 from the simple_app custom template in the current directory:

 
$ tt create simple_app --name app1

Application templates are directories with files.

The main file of a template is its manifest. It defines how the applications are instantiated from this template.

A template manifest is a YAML file named MANIFEST.yaml. It can contain the following sections:

• description – the template description.
• vars – template variables.
• pre-hook and post-hook – paths to executables to run before and after the template instantiation.
• include – a list of files to keep in the application directory after instantiation. If this section is omitted, the application will contain all template files and directories.

All sections are optional.

Example:

 
description: Template descriptionvars:  - prompt: User name    name: user_name    default: admin    re: ^\w+$  - prompt: Retry count    default: "3"    name: retry_count    re: ^\d+$pre-hook: ./hooks/pre-gen.shpost-hook: ./hooks/post-gen.shinclude:  - init.lua  - instances.yml

Files and directories of a template are copied to the application directory according to the include section of the manifest (or its absence).

There is a special file type *.tt.template. The content of such files is adjusted for each application with the help of template variables. During the instantiation, the variables in these files are replaced with provided values and the *.tt.template extension is removed.

Templates variables are replaced with their values provided upon the instantiation.

All templates have the name variable. Its value is taken from the --name option.

To add other variables, define them in the vars section of the template manifest. A variable can have the following attributes:

• prompt: a line of text inviting to enter the variable value in the interactive mode. Required.
• name: the variable name. Required.
• default: the default value. Optional.
• re: a regular expression that the value must match. Optional.

Example:

 
vars:  - prompt: Cluster cookie    name: cluster_cookie    default: cookie    re: ^\w+$

Variables can be used in all file names and the content of *.tt template files.

To use a variable, enclose its name with a period in the beginning in double curly braces: {{.var_name}} (as in the Golang text templates syntax).

Examples:

• init.lua.tt.template file:

   
  local app_name = {{.name}}local login = {{.user_name}}

• A file name {{.user_name}}.txt

Variables receive their values during the template instantiation. By default, tt create asks you to provide the values interactively. You can use the -s (or --non-interactive) option to disable the interactive input. In this case, the values are searched in the following order:

• In the --var option. Pass a string of the var=value format after the --var option. You can pass multiple variables, each after a separate --var option:

   
  $ tt create template app --var user_name=admin

• In a file. Specify var=value pairs in a plain text file, each on a new line, and pass it as the value of the --vars-file option:

   
  $ tt create template app --vars-file variables.txt

  variables.txt can look like this:

   
  user_name=adminpassword=p4$$w0rdversion=2

If a variable isn't initialized in any of these ways, the default value from the manifest is used.

You can combine different ways of passing variables in a single call of tt create.

By default, the application appears in the directory named after the provided application name (--name value).

To change the application location, use the -dst option.

Path to the directory where the application will be created.

Force rewrite the application directory if it already exists.

Application name.

Non-interactive mode.

Variable definition. Usage: --var var_name=value.

Path to the file with variable definitions.