FreshConnection allows access to Mysql slave servers in Rails.
ActiveRecord can only access a single server by default.
FreshConnection can access to replicated Mysql slave servers via a loadbalancer.
Rails ------------ Mysql(Master) | | +------ Mysql(Slave1) | | +---- Loadbalancer ---+ | +------ Mysql(Slave2)
When Rails controller's action begins, FreshConnction connects with one of slave servers behind the loadbalacer.
Read query goes to the slave server via the loadbalancer.
Write query goes to the master server. Inside transaction, all queries go to the master server.
All Mysql connections is disconnected at the end of the Rails controller's action.
Read query goes to the slave server.
Article.where(:id => 1)
If you want to access to the master server, use read_master.
Article.where(:id => 1).read_master
It is possible to use readonly(false) instead of read_master, but it is depricated.
In transaction, All queries go to the master server.
Article.transaction do Article.where(:id => 1) end
Create, Update. Delete queries go to the master server.
article = Article.create(...) article.title = "FreshConnection" article.save article.destory
Add this line to your application's Gemfile:
And then execute:
Or install it yourself as:
$ gem install fresh_connection
production: adapter: mysql2 encoding: utf8 reconnect: true database: kaeru pool: 5 username: master password: master host: localhost socket: /var/run/mysqld/mysqld.sock slave: username: slave password: slave host: slave
slave is a config to connect to slave servers.
Others will use the master server setting.
use multiple slave servers group
If you may want to use multiple slave groups, write the config to
production: adapter: mysql2 encoding: utf8 reconnect: true database: kaeru pool: 5 username: master password: master host: localhost socket: /var/run/mysqld/mysqld.sock slave: username: slave password: slave host: slave admin_slave: username: slave password: slave host: admin_slaves
And call the establish_fresh_connection method in a model that access to
admin_slave slave group.
class AdminUser < ActiveRecord::Base establish_fresh_connection :admin_slave end
The model of children class will access to same slave group as the parent.
class Parent < ActiveRecord::Base establish_fresh_connection :admin_slave end class AdminUser < Parent end class Benefit < Parent end
AdminUser and Benefit access to
admin_slave slave group.
Declare model that doesn't use slave db
class SomethingModel < ActiveRecord::Base master_db_only! end
If a model that always access to the master server is exist, You write
master_db_only! in the model.
The model that master_db_only model's child is always access to master db.
before_fork do |server, worker| ... ActiveRecord::Base.clear_all_slave_connections! ... end after_fork do |server, worker| ... ActiveRecord::Base.establish_fresh_connection ... end
Slave Connection Manager
Default slave connection manager is FreshConnection::ConnectionManager. If you would like to change slave connection manager, assign yourself slave connection manager.
FreshConnection.connection_manager = MySlaveConnection
Yourself Slave Connection Manager should be inherited FreshConnection::AbstractConnectionManager
class MySlaveConnection < FreshConnection::AbstractConnectionManager def slave_connection # must return object of ActiveRecord::ConnectionAdapters::Mysql2Adapter end def put_aside! # called when end of Rails controller action end def recovery(failure_connection, exception) # called when raise exception to access slave server end end
- Fork it
- Create your feature branch (
git checkout -b my-new-feature)
- Commit your changes (
git commit -am 'Add some feature')
- Push to the branch (
git push origin my-new-feature)
- 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.
First of all, you setting the config of the test mysql server in
bundle install --path .bundle bundle exec appraisal install
This command run the spec suite for all rails versions supported.
bundle exec appraisal rake test