Load rails app config from database - ruby-on-rails

Question

I'd like to load some config settings from the database when my Rails (3.2.13) app starts:
class MyApp < Rails::Application
#...normal config here...
config.action_mailer.raise_delivery_errors = true
config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
:address => SystemSetting.system_smtp_host,
:port => SystemSetting.system_smtp_port,
:user_name => SystemSetting.system_smtp_username,
:password => SystemSetting.system_smtp_password,
:authentication => SystemSetting.system_smtp_authentication,
:enable_starttls_auto => SystemSetting.system_smtp_enable_starttls_auto }
end
But it appears that the database config has not been read at this point. I get an error:
ActiveRecord::ConnectionNotEstablished (ActiveRecord::ConnectionNotEstablished)
How can I accomplish this? Either make Rails initialize the database config first, or ... something else?

Answer 1

Regarding practices: Doing stuff like this can be problematic because your application relies on your database to be full when in fact it should support an empty database. Two examples that I can think of are when you try to create a database from scratch (e.g. rake db:setup), or in tests environments.
However, if have no other choice: I would move the mailer initialization to your system_setting.rb or an initializer (where you are guaranteed to have a connection).
config/initializers/load_system_settings.rb
MyApp::Application.config.action_mailer.raise_delivery_errors = true
MyApp::Application.config.action_mailer.delivery_method = :smtp
MyApp::Application.config.action_mailer.smtp_settings = {
:address => SystemSetting.system_smtp_host,
:port => SystemSetting.system_smtp_port,
:user_name => SystemSetting.system_smtp_username,
:password => SystemSetting.system_smtp_password,
:authentication => SystemSetting.system_smtp_authentication,
:enable_starttls_auto => SystemSetting.system_smtp_enable_starttls_auto
}

Answer 2

Manually connect and load values from database.
class Application < Rails::Application
# Set your app path
app_base = 'MY_APPLICATION_PATH'
# Load db configs
db_yml = YAML.load_file("#{app_base}/config/database.yml")["production"]
# Establish db connection
ActiveRecord::Base.establish_connection(:adapter=>db_yml['adapter'], :database=>db_yml['database'], :username=>db_yml['username'], :password=>db_yml['password'])
# load model if not
require "#{app_base}/app/model/system_setting.rb" unless defined?('SystemSetting')
#...normal config here...
config.action_mailer.raise_delivery_errors = true
config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
:address => SystemSetting.system_smtp_host,
:port => SystemSetting.system_smtp_port,
:user_name => SystemSetting.system_smtp_username,
:password => SystemSetting.system_smtp_password,
:authentication => SystemSetting.system_smtp_authentication,
:enable_starttls_auto => SystemSetting.system_smtp_enable_starttls_auto }
#close sql connection after loaded
ActiveRecord::Base.connection.close
end