Load Balancing Databases with Rails

LDAP, the Lightweight Directory Access Protocol, is a database system optimized for user directory information. It is most often used in large organizations, integrated with the enterprise authentication and email systems. However, it is a database in its own right. We do not have space to cover LDAP in detail, but there are many resources available for working with LDAP in Rails.

ActiveLDAP

The ActiveLDAP library (http://ruby-activeldap.rubyforge.org/) is an almost drop-in replacement for ActiveRecord that uses LDAP instead of an RDBMS as a backend. To use it from Rails, set up a configuration file, config/ldap.yml, as follows:

  development:
    host: (ldap server name)
    port: 389
    base: dc=mycompany,dc=com
    password: my_password

  production:
    ...

Then, at the bottom of config/environment.rb, set up the connection:

  ldap_path = File.join(RAILS_ROOT,"config","ldap.yml")
  ldap_config = YAML.load(File.read(ldap_path))[RAILS_ENV]
  ActiveLDAP::Base.establish_connection(ldap_config)

To set up ActiveLDAP, just subclass ActiveLDAP::Base and set the LDAP mapping on a class-by-class basis:

  class Employee < ActiveLDAP::Base
    ldap_mapping :prefix => "ou=Employees"
  end

LDAP queries can then be executed using the class methods on ActiveLDAP::Base:

  @dan = Employee.find :attribute => "cn", :value => "Dan"