In which I talk about how we use globals in Basecamp to provide access to the current user and request details, and fish against those globals deep inside the code base.
I mistakenly said in the video that this is a feature of Rails 5.1. It's not, it's for the upcoming Rails 5.2 release. You can see the edge docs here: http://edgeapi.rubyonrails.org/classes/ActiveSupport/CurrentAttributes.html