active-record-override-railtie.rb

# drop this in an initializer
class ActiveRecordOverrideRailtie < Rails::Railtie
  initializer "active_record.initialize_database.override" do |app|

    ActiveRecord::Base.connection_pool.disconnect!

    ActiveSupport.on_load(:active_record) do
      if url = ENV['DATABASE_URL']
        parsed_url = URI.parse(url)
        establish_connection( {
          adapter:             'postgres',
          host:                parsed_url.host,
          encoding:            'unicode',
          database:            parsed_url.path.split("/")[-1],
          port:                parsed_url.port,
          username:            parsed_url.user,
          password:            parsed_url.password,
          pool:                ENV['DB_POOL'] || 2,
          statement_timeout:   30000,
          reaping_frequency:   10
        })
      else
        ActiveRecord::Base.configurations = app.config.database_configuration
      end
    end
  end
end