Replicat

master-slave replication helper for ActiveRecord.

Installation

# Gemfile
gem "replicat"

Usage

Modify your replicable models & config/database.yml.

model

# app/models/user.rb
class User < ActiveRecord::Base
  replicate
end

# config/database.yml
production:
  adapter: mysql2
  encoding: utf8
  host: 192.168.24.1
  port: 3306
  replications:
    slave1:
      adapter: mysql2
      encoding: utf8
      host: 192.168.24.2
      port: 3306
    slave2:
      adapter: mysql2
      encoding: utf8
      host: 192.168.24.3
      port: 3306
    slave3:
      adapter: mysql2
      encoding: utf8
      host: 192.168.24.4
      port: 3306

replication

Now SELECT queries of User model will be sent to slave connections.

# INSERT query is sent to master.
User.create(name: "replicat")

# SELECT query is sent to slave.
User.first

using

using can help you specify particular connection. When you want to send queries to master, you can use using(:master) to do that (:master is reserved name for using method). When you want to send queries to a particular slave, you can use the slave's name on database.yml like using(:slave1).

# SELECT query is sent to master.
User.using(:master).first

# INSERT query is sent to slave1.
User.using(:slave1).create(name: "replicat")

# :slave1 is used for User connection in the passed block.
User.using(:slave1) { blog.user }

round-robin

slave connections are balanced by round-robin way.

User.first # sent to slave1
User.first # sent to slave2
User.first # sent to slave3
User.first # sent to slave1
User.first # sent to slave2
User.first # sent to slave3
User.first # sent to slave1
User.first # sent to slave2
User.first # sent to slave3

multi master-slave set

Pass the master's connection name to replicate method.

# app/models/user.rb
class User < ActiveRecord::Base
  replicate "production_user"
end

# app/models/recipe.rb
class Recipe < ActiveRecord::Base
  replicate "production_recipe"
end

# config/database.yml
production_user:
  <<: *production
  host: 192.168.24.1
  replications:
    slave1:
      <<: *slave
      host: 192.168.24.2
    slave2:
      <<: *slave
      host: 192.168.24.3
    slave3:
      <<: *slave
      host: 192.168.24.4

production_recipe:
  <<: *production
  host: 192.168.24.5
  replications:
    slave1:
      <<: *slave
      host: 192.168.24.6
    slave2:
      <<: *slave
      host: 192.168.24.7
    slave3:
      <<: *slave
      host: 192.168.24.8

For contributors

# setup gems
bundle install

# setup database
cd spec/dummy
rake db:create
rake db:schema:load RAILS_ENV=test
cd ../../

# run tests
bundle exec rspec