EbisuConnection

EbisuConnection allows access to replica servers.
You could assign a performance weight to each replica server.

Rails ------------ Master DB
             |
             | 
             +---- Replica1 DB (weight 10)
             |
             |
             +---- Replica2 DB (weight 20)

If you could put a load balancer in front of replica servers, should use FreshConnection.

Read query goes to the replica server.

Article.where(:id => 1)

If read query want to access to the master server, use read_master.
In before version 0.3.1, can use readonly(false).

Article.where(:id => 1).read_master

In transaction, All queries go to the master server.

Article.transaction do
  Article.where(:id => 1)
end

Create, Update and Delete queries go to the master server.

article = Article.create(...)
article.title = "FreshConnection"
article.save
article.destory

EbisuConnection supports ActiveRecord version 5.0 or later. If you are using Rails 4.2, you can use EbisuConnection version 2.4.2 or before.

EbisuConnection supports MySQL and PostgreSQL.

Add this line to your application's Gemfile:

gem 'ebisu_connection'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ebisu_connection

config/database.yml

default: &default
  adapter: mysql2
  encoding: utf8
  pool: <%%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: root
  password:

production:
  <<: *default
  database: blog_production
  username: master_db_user
  password: <%= ENV['MASTER_DATABASE_PASSWORD'] %>
  host: master_db

  replica:
    username: replica_db_user
    password: <%= ENV['REPLICA_DATABASE_PASSWORD'] %>

replica is the configuration used for connecting read-only queries to the database replica. All other connections will use the database master settings.

Config of each replica server fill out to config/replica.yml

production:
  - "replica1, 10"
  - "replica2, 20"
  -
    host: "replica3"
    weight: 30

"hostname, weight"

String format is it. You can write config with hash.

If you may want to user multiple replica group, write multiple replica group to config/database.yml.

default: &default
  adapter: mysql2
  encoding: utf8
  pool: <%%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: root
  password:

production:
  <<: *default
  database: blog_production
  username: master_db_user
  password: <%= ENV['MASTER_DATABASE_PASSWORD'] %>
  host: master_db

  replica:
    username: replica_db_user
    password: <%= ENV['REPLICA_DATABASE_PASSWORD'] %>

  admin_replica:
    username: admin_replica_db_user
    password: <%= ENV['ADMIN_REPLICA_DATABASE_PASSWORD'] %>

Config of each replica server fill out to config/replica.yml

production:
  replica:
    - "replica1, 10"
    - "replica2, 20"
    -
      host: "replica3"
      weight: 30
  admin_replica:
    - "replica4, 10"
    - "replica5, 20"

The custom replica stanza can then be applied as an argument to the establish_fresh_connection method in the models that should use it. For example:

class AdminUser < ActiveRecord::Base
  establish_fresh_connection :admin_replica
end

The child (sub) classes of the configured model will inherit the same access as the parent class. Example:

class Parent < ActiveRecord::Base
  establish_fresh_connection :admin_replica
end

class AdminUser < Parent
end

class Benefit < Parent
end

The AdminUser and Benefit models will access the database configured for the admin_replica group.

It is possible to declare that specific models always use the DB master for all connections, using the master_db_only! method:

class SomethingModel < ActiveRecord::Base
  master_db_only!
end

All queries generated by methods on the CustomerState model will be directed to the DB master.

before_fork do |server, worker|
  ...
  ActiveRecord::Base.clear_all_replica_connections!
  ...
end

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

I'm glad that you would do test! To run the test suite, you need mysql installed. How to setup your test environment.

./bin/setup

This command run the spec suite for all rails versions supported.

./bin/test