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

replidog

Development

Runtime