Application environment

This section provides a high-level overview on how to prepare a Tarantool application for deployment and how the application's environment and layout might look. This information is helpful for understanding how to administer Tarantool instances using tt CLI in both development and production environments.

The main steps of creating and preparing the application for deployment are:

1. admin-instance_config-init-environment.
2. admin-instance_config-develop-app.
3. admin-instance_config-package-app.

In this section, a sharded_cluster_crud application is used as an example. This cluster includes 5 instances: one router and 4 storages, which constitute two replica sets.

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$ lsbin  distfiles  include  instances.enabled  modules  templates  tt.yaml

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

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_crud│       ├── config.yaml│       ├── instances.yaml│       ├── router.lua│       ├── sharded_cluster_crud-scm-1.rockspec│       └── storage.lua├── modules├── templates└── tt.yaml

The sharded_cluster_crud 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_crud-scm-1.rockspec: specifies the required external dependencies (for example, vshard and crud).
• storage.lua: includes code specific for storages.

You can find the full example here: sharded_cluster_crud.

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_crud application:

 
~/myapp$ tree -a.├── bin│   ├── tarantool│   └── tt├── instances.enabled│   └── sharded_cluster_crud -> ../sharded_cluster_crud├── sharded_cluster_crud│   ├── .rocks│   │   └── share│   │       └── ...│   ├── config.yaml│   ├── instances.yaml│   ├── router.lua│   └── 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_crud: a packed application. In addition to files created during the application development, includes the .rocks directory containing application dependencies (for example, vshard and crud).
• tt.yaml: a tt configuration file.

When deploying a distributed cluster application from a .tar.gz archive, you can define instances to run on each machine by changing the content of the instances.yaml file.

• On the developer's machine, this file might include all the instances defined in the cluster configuration.

  

  instances.yaml:

 
storage-a-001:storage-a-002:storage-b-001:storage-b-002:router-a-001:

• In the production environment, this file includes instances to run on the specific machine.

  

  instances.yaml (Server-001):

   
  router-a-001:

  instances.yaml (Server-002):

   
  storage-a-001:storage-b-001:

  instances.yaml (Server-003):

   
  storage-a-002:storage-b-002:

The Starting and stopping instances section describes how to start and stop Tarantool instances.

Tarantool applications installed from DEB and RPM packages built with tt pack can run as systemd services. They run on behalf of the tarantool system user. It is created automatically during the package installation.

By default, the application artifacts are placed in the following directories:

• /var/lib/tarantool/sys_env – application data
• /var/log/tarantool/sys_env – logs
• /var/run/tarantool/sys_env – runtime artifacts

If you want to change these directories, make sure that the tarantool user has enough permissions on the directories you use.