Yellowbrick: an email blogging example

Yellowbrick is a small sinatra blog designed to run on Heroku. It combines several of Heroku’s addons such as MongoHQ and Sendgrid. Using the skeleton Git repository, you can be up and rolling with your own blog similar to that of Tumblr, but configurable down to the last snippet of code.


Simple: learning. Yellowbrick is an easy way to help get a grasp of programatically dealing with incoming emails. Also, there’s some definite cool factor to running your own custom blog over taking the de facto. Finally, it’s extensible; there’s no limit as to what you can create when the source is yours.


First of all, Yellowbrick requires that you own a domain and have control over its DNS settings. If you don’t have a Heroku account, Git, and Ruby go grab those now too.

Also, you need the bundler, heroku, and thin gems installed.

$ sudo gem install bundler heroku thin

Getting Some Source

Pull down a copy of the skeleton from Github and enter the directory

$ git clone git://github.com/statianzo/yellowbrick.git
$ cd yellowbrick

Yellowbrick consist of a relatively simple structure. yellowbrick.rb is the core of the app, handling incoming requests. boot.rb loads dependencies and sets up the database. config.ru prepares the app to be run on Heroku.

The models and views directories contain the models and views for the app, respectively.

Running Locally

To start up Yellowbrick locally, you first need to install the Gemfile’s gems

$ bundle install

Second, you need to have the environment variable MONGOHQ_URL pointed to an instance of MongoDB. For a local instance you could use the following:

$ export MONGOHQ_URL='mongodb://localhost/yellowbrick'

And finally, start the thin webserver

$ thin start

If you browse to localhost:3000 you should be met with an empty Yellowbrick blog. To send a sample post, use curl

$ curl -d "subject=MyPost&text=Body+Goes+Here" http://localhost:3000/receive

Refreshing will show your post

Preparing Heroku

Running locally and posting via command line is not too exciting. Blogs are all about web presence. Let’s get some.

Create a new Heroku app using the heroku command line tool. Set up the Sendgrid and MongoHQ addons. Push to the heroku remote repository.

$ heroku create <app_name_here>
$ heroku addons:add mongohq:free
$ heroku addons:add sendgrid:free
$ git push heroku master

Your site should now be usable the same as your local instance. Heroku’s MongoHQ addon automatically sets up the MONGOHQ_URL, and will point to the correct location.

Set Up Sendgrid

Yellowbrick is functional now. However, to have the ability to receive and handle emails, Sendgrid must be configured. Sendgrid provides a feature to parse an email sent to a doma and POST it to a specified url.

If your domain’s DNS settings are controlled by your domain provider, go to their site, and add an additional mx record that points to mx.sendgrid.net.

Retrieve your Sendgrid credentials from Heroku

$ heroku config

Log into the Sendgrid website, enter the Developers - Parse Incoming section where you can set up a hostname to receive emails at (watch.yourdomain.com) and the url to hit when an email arrives, yourapp.heroku.com/receive. It may take up to a half hour while your mx record is getting set up.

Send an email with a subject and body to anything@watch.yourdomain.com, and in moments, the contents should be displayed on your heroku site.

Extending Yellowbrick

As is, Yellowbrick is raw and not secure against anyone else getting their hands on the email address to post to your blog. An initial enhancement could be to add additional restrictions and preventing senders who are not your email using the params[:to].

Read more about what parameters are sent in Sendgrid’s API documentation.

06 Aug 2010