FreshConnection

FreshConnection supports to connect with Mysql slave servers via Load Balancers. All connections will be disconnected every time at the end of the action.

Installation

For Rails3 and 4

Add this line to your application's Gemfile:

gem "fresh_connection"

And then execute:

$ bundle

Or install it yourself as:

$ gem install fresh_connection

Config

config/database.yml

production:
  adapter: mysql2
  encoding: utf8
  reconnect: true
  database: kaeru
  pool: 5
  username: master
  password: master
  host: localhost
  socket: /var/run/mysqld/mysqld.sock

  slave:
    username: slave
    password: slave
    host: slave

slave is config to connect to slave servers. Others will use the master setting. If you want to change, write in the slave.

use multiple slave servers group

If you may want to user multiple slave group, write multiple slave group to config/database.yml.

production:
  adapter: mysql2
  encoding: utf8
  reconnect: true
  database: kaeru
  pool: 5
  username: master
  password: master
  host: localhost
  socket: /var/run/mysqld/mysqld.sock

  slave:
    username: slave
    password: slave
    host: slave

  admin_slave:
    username: slave
    password: slave
    host: admin_slaves

And call establish_fresh_connection method in model that access to admin_slave slave group.

class AdminUser < ActiveRecord::Base
  establish_fresh_connection :admin_slave
end

The children is access to same slave group of parent.

class Parent < ActiveRecord::Base
  establish_fresh_connection :admin_slave
end

class AdminUser < Parent
end

class Benefit < Parent
end

AdminUser and Benefit access to admin_slave slave group.

Declare model that doesn't use slave db

class SomethingModel < ActiveRecord::Base
  master_db_only!
end

If model that always access to master servers is exist, You may want to write master_db_only! in model. The model that master_db_only model's child is always access to master db.

Slave Connection Manager

Default slave connection manager is FreshConnection::ConnectionManager. If you would like to change slave connection manager, assign yourself slave connection manager.

config/initializers/fresh_connection.rb

FreshConnection.connection_manager = MySlaveConnection

Yourself Slave Connection Manager should be inherited FreshConnection::AbstractConnectionManager

class MySlaveConnection < FreshConnection::AbstractConnectionManager
  def slave_connection
    # must return object of ActiveRecord::ConnectionAdapters::Mysql2Adapter
  end

  def put_aside!
    # called when end of Rails controller action
  end

  def recovery(failure_connection, exception)
    # called when raise exception to access slave server
  end
end

Usage

Read query will be access to slave server.

Article.where(:id => 1)

If you want to access to master saver, use readonly(false).

Article.where(:id => 1).readonly(false)

In transaction, Always will be access to master server.

Article.transaction do
  Article.where(:id => 1)
end

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

Test

I'm glad that you would do test! To run the test suite, you need mysql installed. How to setup your test environment.

bundle install --path bundle
GEM_HOME=bundle/ruby/(your ruby version) gem install bundler --pre
bundle exec appraisal install

This command run the spec suite for all rails versions supported.

bundle exec appraisal rake spec