# EbisuConnection

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EbisuConnection supports to connect with Mysql slave servers. It doesn't need Load Balancer.
You can assign a performance weight to each slave server. And slave config is reflected dynamic.
EbisuConnection uses FreshConnection (https://github.com/tsukasaoishi/fresh_connection).

## 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

      slave:
        username: slave
        password: slave
        host: slave

```slave``` is base config to connect to slave servers.
Others will use the master setting. If you want to change, write in the slave.

Config of each slave server fill out config/slave.yaml

    production:
      - "slave1, 10"
      - "slave2, 20"
      -
        host: "slave3"
        weight: 30

config/slave.yaml is checked by end of action. If config changed, it's reflected dynamic. Application doesn't need restart.

    "hostname, weight"

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

### use multiple slave servers group
If you may want to user multiple slave group, write multiple slave 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

      slave:
        username: slave
        password: slave
        host: slave

      admin_slave:
        username: slave
        password: slave
        host: admin_slaves

Config of each slave server fill out config/slave.yaml

    production:
      slave:
        - "slave1, 10"
        - "slave2, 20"
        -
          host: "slave3"
          weight: 30
      admin_slave:
        - "slave3, 10"
        - "slave4, 20"


And call establish_fresh_connection method in model that access to ```admin_slave``` slave group.

    class AdminUser < ActiveRecord::Base
      establish_fresh_connection :admin_slave
    end

The children is access to same slave group of 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 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.

## Usage

Read query will be access to slave server.

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

If you want to access to the master server, use read_master.

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

It is possible to use readonly(false) instead of read_master, but it will be depricated at future version.

In transaction, Always will be access to master server.

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

```bash
bundle install --path .bundle
GEM_HOME=.bundle/ruby/(your ruby version) gem install bundler --pre
bundle exec appraisal install
```

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

```base
bundle exec appraisal rake spec
```