Managing multiple instances

Application directory

To create an application that runs on multiple instances, prepare its configuration in a directory. The directory name is used as the application’s identifier.

This directory should contain the following files:

• The application file named init.lua.

• The instances configuration file instances.yml with instance names followed by colons:

  <instance_name1>:
  <instance_name2>:
  ...
  

  Note

  Do not use the dot (.) and dash (-) characters in the instance names. They are reserved for system use.

• (Optional) Application files to run on specific instances. These files should have names <instance_name>.init.lua, where <instance_name> is the name specified in instances.yml. For example, if your application has separate source files for the router and storage instances, place the router code in the router.init.lua file.

Identifying instances in code

When the application is working, each instance has associated environment variables TARANTOOL_INSTANCE_NAME and TARANTOOL_APP_NAME. You can use them in the application code to identify the instance on which the code runs.

To obtain the instance and application names, use the following code:

local inst_name = os.getenv('TARANTOOL_INSTANCE_NAME')
local app_name = os.getenv('TARANTOOL_APP_NAME')

Example

The demo application runs on three instances: master and replica for storing data and router for connections. master and replica share the same code, and router has its own code.

The application configuration is stored in the demo directory. The directory contains the following files:

• instances.yml – the instances configuration:

  master:
  replica:
  router:
  

• init.lua – the code of master and replica.

• router.init.lua – the code of router.

Start all three instances of the demo application:

tt start demo

Check the status of demo instances:

tt status demo

Check the status of a specific instance:

tt status demo:replica

Connect to an instance:

tt connect demo:router

Stop a specific instance:

tt stop demo:replica

Stop all demo instances:

tt stop demo