The Carbon Emitter

I still see people promoting various gems and plugins to handle miscellaneous configuration elements for your application. One little known secret is that Rails 3 allows you to define your own configuration elements trivially.

In this case, I wanted to use the nifty wkhtmltopdf utility to create a PDF. I was able to call the binary just fine with Homebrew on OSX but found that I had to use a custom binary checked into git for our production environment on Heroku. So I created a configuration variable to store where wkhtmltopdf could be found in the current environment.

First, we define a default value for all environments in config/application.rb:

module Configurator
  class Application < Rails::Application
    # By default, let OSX resolve the path to the binary
    config.wkhtmltopdf = "wkhtmltopdf"
  end
end

Then we override the default setting as necessary in config/environments/:

Configurator::Application.configure do
  # Settings specified here will take precedence over those in config/application.rb

  # Point Heroku explicitly to the binary we need to use
  config.wkhtmltopdf = "#{Rails.root}/bin/wkhtmltopdf"
end

Lastly, we access the configuration element in our code:

  cmd = [Configurator::Application.config.wkhtmltopdf, url, tmpfile.path]

Yes, that’s it. Just use Rails’s environment support and config to store your own configuration elements. They’re trivial to set, trivial to access and require no third-party gems or custom text files.

The good folks at Instagram posted a fun challenge on their engineering blog recently:

"Your challenge, if you choose to accept it, is to write a simple script that takes a shredded image in as input and outputs an unshredded and reconstituted image. That is, imagine if you took an image, divided it into an even number of columns and shuffled those columns randomly to produce a shredded image. Then, take that image into the script and output the original image."

(The original post is here: Instagram Engineering Challenge: The Unshredder).

This struck me as a great opportunity to hack out some code in Go (rev 60.1) as part of my continuing exploration of the language and its packages.

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We are heavy users of Pivotal Tracker here at Carbon Five, and each project evolves workflows around its use. I recently spent some time writing a Chrome extension to help support some of the common interaction patterns that come up in our workflows.

This blog post is not about that.

I started to write up a post about the Chrome extension and how I developed it (forthcoming), but realized that I needed to show screenshots. Unfortunately, I can’t use images of a client’s production tracker. Hmm.

I quickly whacked together a Ruby script to generate realistic-looking stories in a tracker project. Here it is!

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