Application environment

Initializing a local environment

Before creating an application, you need to set up a local environment for tt:

1. Create a home directory for the environment.

2. Run tt init in this directory:

   ~/myapp$ tt init
      • Environment config is written to 'tt.yaml'
   

This command creates a default tt configuration file tt.yaml for a local environment and the directories for applications, control sockets, logs, and other artifacts:

~/myapp$ ls
bin  distfiles  include  instances.enabled  modules  templates  tt.yaml

Find detailed information about the tt configuration parameters and launch modes on the tt configuration page.

Creating and developing an application

You can create an application in two ways:

• Manually by preparing its layout in a directory inside instances_enabled. The directory name is used as the application identifier.
• From a template by using the tt create command.

In this example, the application’s layout is prepared manually and looks as follows.

~/myapp$ tree
.
├── bin
├── distfiles
├── include
├── instances.enabled
│   └── sharded_cluster
│       ├── config.yaml
│       ├── instances.yaml
│       ├── router.lua
│       ├── sharded_cluster-scm-1.rockspec
│       └── storage.lua
├── modules
├── templates
└── tt.yaml

The sharded_cluster directory contains the following files:

• config.yaml: contains the configuration of the cluster. This file might include the entire cluster topology or provide connection settings to a centralized configuration storage.
• instances.yml: specifies instances to run in the current environment. For example, on the developer’s machine, this file might include all the instances defined in the cluster configuration. In the production environment, this file includes instances to run on the specific machine.
• router.lua: includes code specific for a router.
• sharded_cluster-scm-1.rockspec: specifies the required external dependencies (for example, vshard).
• storage.lua: includes code specific for storages.

You can find the full example here: sharded_cluster.

Packaging the application

To package the ready application, use the tt pack command. This command can create an installable DEB/RPM package or generate .tgz archive.

The structure below reflects the content of the packed .tgz archive for the sharded_cluster application:

~/myapp$ tree -a
.
├── bin
│   ├── tarantool
│   └── tt
├── include
├── instances.enabled
│   └── sharded_cluster -> ../sharded_cluster
├── modules
├── sharded_cluster
│   ├── .rocks
│   │   └── share
│   │       └── ...
│   ├── config.yaml
│   ├── instances.yaml
│   ├── router.lua
│   ├── sharded_cluster-scm-1.rockspec
│   └── storage.lua
└── tt.yaml

The application’s layout looks similar to the one defined when developing the application with some differences:

• bin: contains the tarantool and tt binaries packed with the application bundle.
• instances.enabled: contains a symlink to the packed sharded_cluster application.
• sharded_cluster: a packed application. In addition to files created during the application development, includes the .rocks directory containing application dependencies (for example, vshard).
• tt.yaml: a tt configuration file.