= ey_cloud_awareness

Make your EngineYard cloud instances aware of each other.

Never download a new <tt>deploy.rb</tt> again.

== Quick start

Put this in <tt>config/environment.rb</tt>:

  config.gem 'ey_cloud_awareness', :version => '[WHATEVER THE CURRENT GEM VERSION IS]', :lib => false, :source => 'http://gemcutter.org'

Put this in your <tt>config/deploy.rb</tt> (or wherever your deploy-related Capfile is):

  load "#{Gem.searcher.find('ey_cloud_awareness').full_gem_path}/lib/tasks/capistrano_tasks.rb"

  task :my_app_production do
    role :app_master, 'my_app.com'          # or you can use its Elastic IP
    set :rails_env, 'production'            # required
    set :deploy_to, '/data/my_app'          # required
    find_and_execute_task 'eyc_setup'       # note that we don't use eyc: namespace
  end

  task :my_app_staging do
    role :app_master, 'staging.my_app.com'  # or you can use its Elastic IP
    set :rails_env, 'production'            # required
    set :deploy_to, '/data/my_app'          # required
    find_and_execute_task 'eyc_setup'       # note that we don't use eyc: namespace
  end
  
  # add more tasks if you have more cloud environments

Now you should be able to eycap stuff like:

  cap my_app_production monit:status

...and <b>capistrano will always have a fresh list of your environment's instances</b>. Roles like <tt>:app</tt>, <tt>:db</tt>, and <tt>:utility</tt> are set properly.

== Just dumping information about your instances

Once you've done the quickstart, try:

  cap my_app_production eyc:app         # gets a list of your app instances, including app_master
  cap my_app_production eyc:utility     # ditto for utility instances
  cap my_app_production eyc:db          # gets your master db instance (FIXME: I don't think it will find slaves)
  cap my_app_production eyc:all         # gets a list of all your instances

== Using the EngineYardCloudInstance class inside Rails

I run a memcached server on every app instance, so I have this in <tt>config/environment.rb</tt>:

  Rails::Initializer.run do |config|
    [...]
    config.cache_store = :mem_cache_store, EngineYardCloudInstance.app.map { |i| "#{i.private_dns_name}:11211" }
    [...]
  end

Or whatever you want:

  >> all_app_instances = EngineYardCloudInstance.app      
  => [#<EngineYardCloudInstance:0xb5e12f70 @instance_id="i-50cf5838">, #<EngineYardCloudInstance:0xb5e12f5c @instance_id="i-dc9207b4">, #<EngineYardCloudInstance:0xb5e12f34 @instance_id="i-b2d84fda">]
  >> all_app_instances.first.dns_name
  => "ec2-67-202-43-40.compute-1.amazonaws.com"
  >> pp all_app_instances.first.to_hash
  {:dns_name=>"ec2-67-202-43-40.compute-1.amazonaws.com",
   :instance_role=>"app",
   :aws_groups=>["ey-app1_production-1256085955-3205-13340"],
   :aws_instance_id=>"i-50cf5838",
   :private_dns_name=>"domU-12-31-39-01-99-D3.compute-1.internal",
   :aws_state=>"running"}
  => nil

== A note on EngineYard dependence

This gem depends on

  /etc/chef/dna.json

being present and containing certain attributes as named by EngineYard. Please let me know if something changes.

== A note on caching and network needs

I tried to be smart about caching the results of network calls.

Stuff like the current instance id, which is pulled from an EC2 metadata server, is stored in

  CURRENT_INSTANCE_ID_CACHE_PATH = defined?(RAILS_ROOT) ? "#{RAILS_ROOT}/config/engine_yard_cloud_instance_id" : '/etc/engine_yard_cloud_instance_id'

Please let me know if this causes problems.

== Copyright

Copyright (c) 2009 Seamus Abshere. See LICENSE for details.