database.yml.erb

#
# This file should be in .../cookbooks/database/templates/default/database.yml.erb
#

<%= @environment %>:
  adapter:   <%= @adapter %>
  database:  <%= @database %>
  username:  <%= @username %>
  password:  <%= @password %>
  host:      <%= @host %>
  reconnect: true

# This produces a block for each slave, named "slave", "slave_1", "slave_2", etc.
<% @slaves.each_with_index do |slave,i| %>
<%= i == 0 ? "slave" : "slave_#{i}" %>:
  slavename: <%= slave["name"].nil? ? "---" : "'"+slave["name"]+"'" %>
  adapter:   <%= @adapter %>
  database:  '<%= @dbname %>'
  username:  '<%= @dbuser %>'
  password:  '<%= @dbpass %>'
  host:      '<%= slave['private_hostname'] %>'
  reconnect: true
<% end %>

default.rb

#
# Cookbook Name: database
# Recipe: default
#
# Description:
# Configure application servers to use mysql2 adapter for the database.yml config.
# All parameters except the adapter are pulled from the EY node JSON element. See
# http://docs.engineyard.com/use-deploy-hooks-with-engine-yard-cloud.html for an
# example of the node JSON object. This object is also used for by deploy hooks
# at Engine Yard.
#
# This file should be in .../cookbooks/database/recipes/default.rb
#
#
# Q: Why might we need this custom recipe?
#
# A: You may need to generate a custom database.yml file because Engine Yard's
# default database.yml file generator always generates a config file that uses the
# mysql adapter for Rails 2 apps. (For rails[34] apps in MySQL environents it
# attempts to detect whether the mysql or mysql2 gem is in use.)
#
# This recipes forces the mysql2 adapter for an existing Rails 2 app.
#
# The default database.yml lists any DB replicas in an environment, but some gems
# which distribute reads may require a custom syntax - in such cases the template
# can be modified to produce the appropriate syntax.
#

if ['solo', 'app_master', 'app', 'util'].include?(node[:instance_role])
  # for each application
  node[:engineyard][:environment][:apps].each do |app|

    # create new database.yml
    template "/data/#{app[:name]}/shared/config/database.yml" do
      source 'database.yml.erb'
      owner node[:users][0][:username]
      group node[:users][0][:username]
      mode 0644
      variables({
        :environment => node[:environment][:framework_env],
        :adapter => 'mysql2',
        :database => app[:database_name],
        :username => node[:users][0][:username],
        :password => node[:users][0][:password],
        :host => node[:db_host]
        :slaves => node.environment.instances.select{|i| i["role"] =="db_slave"},
      })
    end
  end
end