This is Sharding Library for ActiveRecord, inspire and import codes from mixed_gauge and activerecord-sharding (Thanks!).

activerecord-shard_for have 3 concepts.

• simple
• small
• pluggable

Add this line to your application's Gemfile:

gem 'activerecord-shard_for'

And then execute:

$ bundle

Or install it yourself as:

$ gem install activerecord-shard_for

Add additional database connection config to database.yml.

# database.yml
production_user_001:
  adapter: mysql2
  username: user_writable
  host: db-user-001
production_user_002:
  adapter: mysql2
  username: user_writable
  host: db-user-002
production_user_003:
  adapter: mysql2
  username: user_writable
  host: db-user-003
production_user_004:
  adapter: mysql2
  username: user_writable
  host: db-user-004

Define cluster in initializers (e.g initializers/active_record_shard_for.rb)

ActiveRecord::ShardFor.configure do |config|
  config.define_cluster(:user) do |cluster|
    # unique identifier, connection name
    cluster.register(0, :production_user_001)
    cluster.register(1, :production_user_002)
    cluster.register(2, :production_user_003)
    cluster.register(3, :production_user_004)
  end
end

Include ActiveRecord::ShardFor::Model to your model class, specify cluster name and router name for the model, specify distkey which determines node to store.

class User < ActiveRecord::Base
  include ActiveRecord::ShardFor::Model
  use_cluster :user, :hash_modulo # hash_modulo is presented by this library.
  def_distkey :email
end

Use .get to retrieve single record which is connected to proper database node. Use .put! to create new record to proper database node.

.all_shards returns each model class which is connected to proper database node. You can query with these models and aggregate result.

User.put!(email: 'alice@example.com', name: 'alice')

alice = User.get('alice@example.com')
alice.age = 1
alice.save!

User.all_shards.flat_map {|m| m.find_by(name: 'alice') }.compact

More imformation and example to see wiki!

Contributors are welcome! This is what you need to setup your Octopus development environment:

$ git clone https://github.com/yuemori/activerecord-shard_for
$ cd activerecord-shard_for
$ bundle install
$ bundle exec rake appraisal:install
$ bundle exec rake spec

The gem is available as open source under the terms of the MIT License.