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.

Usage

Access to Replica

Read query goes to the replica server.

Article.where(:id => 1)

Access to Master

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

Support ActiveRecord version

EbisuConnection supports ActiveRecord version 4.2 or later. If you are using Rails 4.1 or 4.0, you can use EbisuConnection version 2.1.0 or before. If you are using Rails 3.2, could use EbisuConnection version 1.0.0 or before.

Support DB

EbisuConnection supports MySQL and PostgreSQL.

Installation

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

config/database.yml

production:
  adapter: mysql2
  encoding: utf8
  reconnect: true
  database: kaeru
  pool: 5
  username: master
  password: master
  host: localhost
  socket: /var/run/mysqld/mysqld.sock

  replica:
    username: replica
    password: replica
    host: replica

replica is a config to connect to replica servers.
Others will use the master server 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.

use multiple replica servers group

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

production:
  adapter: mysql2
  encoding: utf8
  reconnect: true
  database: kaeru
  pool: 5
  username: master
  password: master
  host: localhost
  socket: /var/run/mysqld/mysqld.sock

  replica:
    username: replica
    password: replica
    host: replica

  admin_replica:
    username: replica
    password: replica
    host: admin_replica

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"

And call establish_fresh_connection method in model that access to admin_replica replica group.

class AdminUser < ActiveRecord::Base
  establish_fresh_connection :admin_replica
end

The children is access to same replica group of parent.

class Parent < ActiveRecord::Base
  establish_fresh_connection :admin_replica
end

class AdminUser < Parent
end

class Benefit < Parent
end

AdminUser and Benefit access to admin_replica replica group.

Declare model that doesn't use replica db

class SomethingModel < ActiveRecord::Base
  master_db_only!
end

If model that always access to master servers is exist, You may want to write master_db_only! in model. The model that master_db_only model's child is always access to master db.

for Unicorn

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

after_fork do |server, worker|
  ...
  ActiveRecord::Base.establish_fresh_connection
  ...
end

Contributing

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

Test

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