Octoball provides Octopus-like database sharding helpers for ActiveRecord 6.1+. This will make it easier to upgrade Rails to 6.1+ for applications using Octopus gem for database sharding with Rails 4.x/5.x.

Currently, its implementation is focusing on horizontal database sharding. However, by customizing shard key mapping, it can be applied to replication use case too.

• Octopus-like shard swithcing by using class method, e.g.:

  Octoball.using(:shard1) { User.find_by_name("Alice") }
  User.using(:shard1).first

• Each model instance knows which shard it came from so shard will be switched automatically:

  user1 = User.using(:shard1).find_by_name("Bob")
  user2 = User.using(:shard2).find_by_name("Charlie")
  user1.age += 1
  user2.age += 1
  user1.save!  #  Save the user1 in the correct shard `:shard1`
  user2.save!  #  Save the user2 in the correct shard `:shard2`

• Relations such as has_many are also resolved from the model instance's shard:

  user = User.using(:shard1).find_by_name("Alice")
  user.blogs.where(title: "blog")  # user's blogs are fetched from `:shard1`

• Connection handling and configuration -- managed by the native ActiveRecord::Base.connects_to methods introduced in ActiveRecord 6.1.
  • You need to migrate from Octopus' config/shards.yml to Rails native multiple DB configuration using config/database.yml. Please refer the Setup section for more details.
• Migration -- done by ActiveRecord 6.1+ natively.
  • Instead of using method in Octopus, you can specify the migrations_paths parameter in the config/database.yml file.
• Replication handling -- done by ActiveRecord's role
  • round-robin connection scheduler is currently omitted.

gem "octoball"

Define the database connections in config/database.yml, e.g.:

default: &default
  adapter: mysql2
  pool: 5
  username: root
  host: localhost
  timeout: 5000
  connnect_timeout: 5000

development:
  master:
    <<: *default
    database: db_primary
  shard1_connection:
    <<: *default
    database: db_shard1

And define shards and corresponding connections in abstract ActiveRecord model class, e.g.:

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true

  connects_to shards: {
    master: { writing: :master },
    shard1: { writing: :shard1_connection },
  }
end

class User < ApplicationRecord
  ...
end

Optionally, to use the :master shard as a default connection like Octopus, add the following script to config/initializers/default_shard.rb:

ActiveRecord::Base.default_shard = :master

Octoball has rspec tests delived from subsets of Octopus' rspec.

To run the rspec tests, follow these steps:

RAILS_ENV=test bundle exec rake db:prepare
RAILS_ENV=test bundle exec rake spec

Octoball is released under the MIT license.

Original Octopus' copyright: Copyright (c) Thiago Pradi