replidog

Replidog

Multiple mlaster/slave helper for ActiveRecord

Based on https://github.com/r7kamura/replicat

Features

• Multiple master/slave
• Auto switching between master/slave
• Supports connection management and query cache
• Supports Rails 3.2, 4.0, 4,1, 4.2, 5.0, 5.1

Installation

Add this line to your application's Gemfile:

gem 'replidog'

And then execute:

$ bundle

Or install it yourself as:

$ gem install replidog

Usage

configuration

# 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/recipe.rb
class Recipe < RecipeTable
  establish_connection :production_recipe
end

# config/database.yml
production_base:
  adapter: mysql2
  encoding: utf8
  port: 3306
production:
  <<: *production_base
  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_base
  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

If you want to connecto to production_recipe in multiple models, Create Abstract class and extend it.

# app/models/recipe_table.rb
class RecipeTable < ActiveRecord::Base
  self.abstract_class = true
  establish_connection :production_recipe
end

# app/models/recipe.rb
class Recipe < RecipeTable
end

connection management / query cache

To handle all master/slave connections togegher, the methods related with connection management and query cache are overridden. So you don't need to update middlewares and configurations for app servers.

List of overridden methods

• ActiveRecord::Base.clear_active_connections
• ActiveRecord::Base.clear_reloadable_connections
• ActiveRecord::Base.clear_all_connections
• ActiveRecord::Base.connection.enable_query_cache!
• ActiveRecord::Base.connection.disable_query_cache!
• ActiveRecord::Base.connection.clear_query_cache!

Contributing

# setup gems
bundle install
appraisal install

# setup databases
rake db:prepare

# run tests for current gemfile
rake

# run tests for all appraisals
appraisal rake