Distributed transactions in Rails with MySQL

This plugin for Rails provides experimental support for distributed atomic transactions (transaction over multiple database systems) with MySQL. This is accomplished by using the two-phase commit protocol (2PC) in conjunction with the MySQL XA statements

Install

Add the git repository to your project's Gemfile and run bundle install :

gem 'mysql_xa_transaction', :git => 'https://github.com/martijnbolhuis/rails_mysql_xa_transaction.git'

Usage

Set up multiple databases for models in your project. This can be done by using the [connection_ninja plugin](see https://github.com/cherring/connection_ninja for more info).

Connection ninja configuration

Add connection_ninja to your Gemfile gem 'connection_ninja'

class MyModel < ActiveRecord::Base
  use_connection_ninja(:other_database)
end

After your normal configuration in database.yml add a new group:

other_database:
  development:
    adapter: mysql2
    database: database_name
    user: username
    host: 192.168.3.4

  production:
    adapter: mysql2
    database: database_name
    user: username
    host: 192.168.3.4

Transaction

A transaction can be started as follows:

XATransactionCoordinator.XATransaction [KlmTicket, AirFranceTicket] do
  @klm_ticket.save!
  @air_france_ticket.save!
end

The XATransaction method receives an optional list of models that are part of the transaction. When this list is not suplied, it will start a transaction over all models in your project (not recommended!). Be sure to use save! and not save within the transaction block. A boolean value will be returned indicating whether the transaction was successful.

Limitations

Failure of commit or rollback operations are logged to the standard rails logger but recovery is not implemented.