Rails RSpec with Multiple Databases

Question

I run a Rails app, and we\'re in the process of splitting out our signup process to a separate app. The signup app has its own separate database (for CMS and collecting prospect

Answer 1

We have a gem that is basically a collection of ActiveRecord models that connect to our legacy system. In our case we have all those models contained in a module from which all models related to the legacy database connects.

module Legacy
  class Base < ActiveRecord::Base
    establish_connection :legacy
  end

  class User < Base
  end
end

With this setup it makes it really easy to switch out the database connection. If you really go for that automated detection you can put logic in your base class to determine which database to use:

module Legacy
  class Base < ActiveRecord::Base
    if Rails.env == 'test'
      establish_connection :legacy_test
    else
      establish_connection :legacy
   end
end

Or simply tell your module which connection to use in your spec helper:

# spec/spec_helper.rb    
Legacy::Base.establish_connection(ActiveRecord::Base.configurations['legacy_test'])

Personally I would recommend the second option. Of course both solutions depend on namespaced models.

Peer

Answer 2

Ryan, we were also in the process of migrating from one datastore to another. We needed to develop against two databases and maintain separate migrations and fixtures for each.

I created a gem called Secondbase to help with this. Essentially, it allows you to manage two databases seamlessly in a single Rails app. Perhaps it will solve your issue as well: https://github.com/karledurante/secondbase

Answer 3

Here's what I came up with as a mixin:

# lib/establish_connection_to_master_database.rb
module EstablishConnectionToMasterDatabase
  def establish_connection_to_master_database

    case RAILS_ENV
    when "development"
      establish_connection :master_dev
    when "test"
      establish_connection :master_test
    when "production"
      establish_connection :master
    end

  end
end
ActiveRecord::Base.send(:extend, EstablishConnectionToMasterDatabase)

# models/subscription.rb
class Subscription < ActiveRecord::Base
  establish_connection_to_master_database
end

# config/initializers/config.rb
require 'establish_connection_to_master_database'

In order for this to work with RSpec, this needs to be loaded in an initializer - apparently loading it in the environment file causes it to be loaded it too late, and it won't work.

Answer 4

We just used interpolation for this:

class ServiceModel < ActiveRecord::Base
  establish_connection :"main_app_#{Rails.env}"
end

The funny :"main_app_" syntax makes a symbol from a string. This could be also written "main_app_#{Rails.env}".to_sym. In either case with Rails 4.1 this must be a symbol (under 3.2 we had just used a string).