My thinking at the time was that a standalone “wrapper” web service made sense. While it would have complicated application administration a bit, encapsulating the mailing list functionality in a simple service that could be called synchronously or asynchronously, as well as modified and deployed independent of core site logic, sounded reasonable.

So, let’s start with building a minimal Merb application to serve as a foundation:
merb-gen app mail_chimp_service --flat

This generates one controller, a few templates (if we want to build in some templated monitoring and for xml responses) and just enough configuration to get the Merb service started.

To test it out, just fire up Merb with the following command: merb and head to http://localhost:4000.

With a foundation in place, I started looking into my MailChimp plugin to see if I should turn it into a gem or do something simpler. I turned to hoe, thinking that making a gem would be interesting, but then decided otherwise, as I basically didn’t feel like writing that much. So instead, I wrote a simple chimp class to do the MailChimp API work:

require 'xmlrpc/client'
class Chimp
  cattr_accessor :client, :auth
  def add(subscriber)
    chimp_subscribe(auth, Merb::Config[:chimp_settings]['mail_chimp']['mailing_list_id'],
                            subscriber.email, subscriber.mail_merge)
  end
  private
  def chimp_subscribe(auth, mailing_list_id, email, merge_vars,
                                email_content_type="html", double_optin=true)
    begin
      client.call("listSubscribe", auth, mailing_list_id, email,
                     merge_vars, email_content_type, double_optin)
    rescue XMLRPC::FaultException => e
      Merb.logger e.faultCode
      Merb.logger e.faultString
    end
  end
end

This class adds users to a specific MailChimp mailing list using the MailChimp APIs. The client and auth attributes are set in the Merb init.rb class, as they really only need to be loaded once and not initialized per each request:

Merb::BootLoader.after_app_loads do
    Chimp.client = XMLRPC::Client.new2('http://api.mailchimp.com/1.0/')
    Chimp.auth = XMLRPC::Client.new2('http://api.mailchimp.com/1.0/').call("login",
                         Merb::Config[:chimp_settings]['mail_chimp']['username'],
                         Merb::Config[:chimp_settings]['mail_chimp']['password'])
end

I’m loading the MailChimp configuration parameters in the init.rb file in the config block. I’m just loading in a yaml file with the relevant information one would presumably want externalized from the application code:

Merb::Config.use { |c|
 .....
 c[:chimp_settings]      = YAML.load_file(Merb.root/'mailing.yml')
}

I then created a simple subscriber.rb class to encapsulate user elements and wired the relevant classes together in my single controller like so:

require 'chimp'
require 'subscriber'
class Foo < Merb::Controller
  provides  ml

  def _template_location(action, type = nil, controller = controller_name)
    controller == "layout" ? "layout.#{action}.#{type}" : "#{action}.#{type}"
  end

  def index
    subscriber = Subscriber.new(params)
    chimp = Chimp.new
    chimp.add(subscriber)
    render false
  end
end

I subsquently added an index.xml.erb class to my views directory in order to render successful responses, fired up my app with the merb command and then ran a test in a separate console to ensure everything was working:

curl -H "Accept: text/xml" -L -d
"email=matt@mandarinsoda.com&first_name=swanky&last_name=mango" http://localhost:4000

It worked – the very first time!  (joking, but it did work after a bit of tinkering). I saw the content of my index.xml.erb and received a MailChimp opt-in email. Not too shabby for a few hours of tinkering. I’m sure there are interesting Merb features missing as well that could make this all the more compact.  More to explore later.

37 Signals on doing the same

Try them all!

I suppose I could also just listen to Paul Graham and relax…

Except in special kinds of applications, parallelism won’t pervade the programs that are written in a hundred years. It would be premature optimization if it did.

Adam Keys on creating micro-apps using existing infrastructure and APIs like Foamee does with Twitter.

Good presentation on application interface design..

New Rails restful help with the plugin resource_this.

40 design books from Smashing Magazine.

Oracle has built a JRuby application Oracle Mix.

Corkd’s use of microformats is also covered in greater depths in a recent microformats book