Wednesday, January 1, 2014

Sinatra or Rails for "Engineering Software as a Service" MOOC and book?

Happy new year!

Thanks to all the students and instructors who are trying out our Engineering Software as a Service book or MOOC.

We are trying to improve the ESaaS book and course in two ways, and want your opinions.

  1. Survey results of Berkeley students show that many of them still have some trouble with Rails by the end of the 14-week semester.  For a few it's magic; for the majority, it's at best hit-and-miss, with some parts they understand and some they don't.  Some of our SPOC instructors using the material have reported similar problems.

  2. For potential instructors, having to learn Rails well enough to be able to answer questions about it is likely an obstacle to adoption.


Dave and I were discussing the following question:  if the essence of 169.1x is to understand how the BDD/TDD cycle works in the context of SaaS, could we do that whole class using only the simpler Sinatra framework, with Rails making its first appearance in 169.2x (or in the second half/final third of a full-semester course)?  If so, should we modify the book accordingly?

I've been putting a good bit of time into figuring out the nuts and bolts of what this would entail.  Here's where I am right now, which is an impasse so i want feedback.

TL;DR: Sinatra is likely a good on-ramp, but trying to use it for all of Cs169.1x does not remove Rails's complexity - it just replaces it with a slightly smaller amount of complexity that has to be hand-built.  (That may not necessarily be bad, and has to be weighed against the "instructor obstacle" argument.)

Note that much of what I say below sounds like I'm listing shortcomings of Sinatra, but I'm not: it was designed to be just as it is, because it serves a fundamentally different purpose from Rails.  Our question here is whether that purpose suffices for teaching SaaS basics.

Sinatra is OK for illustrating basic SaaS concepts in an app with no persistent models. These concepts include important SaaS fundamentals like SaaS architecture, client-server, routes, RESTfulness, template views and view rendering, layouts to DRY out views, form submission, redirects, gathering parameters from either a RESTful URL or a form, and sessions & cookies.

It is slightly less intuitive to debug than Rails: if you make a change to a Rails app while it's running (in development), the change takes effect immediately; with Sinatra you need to use a different gem (rerun) to get this behavior.

Sinatra has no architectural opinion: unlike Rails, it doesn't force MVC or any other architecture (save that by default it expects view templates to be in a views directory).  In my view, for beginning students, this is a deficiency.  You have to impose whatever architecture you think is appropriate, pick your own directory structure to reflect it, etc.  So you can nominally talk about MVC and talk about putting the "real app logic" into models vs. into the main Sinatra app file (which can be said to resemble a controller).  But there's only so much you can do without persistent models.

To add persistence, you need to add either ActiveRecord or DataMapper, and because Sinatra doesn't rely on convention over configuration to determine where things go, a fair amount of manual configuration is needed either way.  We could provide boilerplate that performs that configuration, but it's not clear if such boilerplate would be any less "magic" than what is built into Rails to do those tasks now.

Sinatra seems serviceable for illustrating BDD+TDD with Cucumber/Capybara/RSpec/Autotest, but only barely. Unlike Rails, to get Sinatra to work well with these tools, you have to manually configure several things that happen automatically with Rails as a result of gems like cucumber-rails, rspec-rails and so on.  Autotest in particular seems immature with Sinatra, and a big part of convincing students to actually use BDD and TDD (in my view) is that with Autotest running you don't have to "interrupt" your coding just to run tests.  This could probably be fixed, but again, we'd end up providing some boilerplate that is impenetrable Ruby for a beginner, whereas Autotest works with Rails 'out of the box'.

The difference is most visible when creating a new app (and we informally had already decided it would be better if students got to create & deploy several small apps by the time they start a big project);

  • Rails:  rails new <appname>, rails generate cucumber:install, rails generate rspec:install, rake db:create

  • Sinatra: manually create a directory structure, config files, database, and other glue needed for Cucumber/Capy and Rspec.  In Rails, the idea of a separate environment & database for testing vs. development is baked in; in Sinatra, so you'd have to manually create code that does that as well, and manually modify Rake tasks (eg) so that tests run against the testing database but the app runs against the development database.


An alternative to trying to use Sinatra for all of 169.1x might be to do a single assignment based on Sinatra in conjunction with the SaaS Architecture chapter, then jump into Rails but simplify the presentation at first. There are a few ways to do this:





















What we do nowWhat we could do that's simpler
Apps with persistent modelsApps whose models don't use the database at first (but use ActiveRecord later)
Resource based routes (resources :movies) which creates lots of distinct action routesSimple string-match routes  (get '/movies', 'MoviesController#index') that map one-to-one onto Ruby methods in the controller
Rely on Convention over Configuration for rendering viewsRender view explicitly from each controller action (render :template => 'index.html.haml', :layout => 'application.html.haml') and later reveal that these are default behaviors and the explicit call can be omitted

Under this model, the main changes to the course/book would be:

  • HW 1: instead of Ruby-only, do a Sinatra app

  • HW 1.5: instead of Ruby-only, do a simplified Rails app

  • HW 2 and later stay more or less the same, possibly with more scaffolding and pointers to Sam's excellent video tutorials to help complete them


Your turn to comment...what combination will best improve student understanding and increase instructor adoption?

No comments:

Post a Comment

Comments are disabled because the only commenters are spammers, despite Google's best efforts. But I welcome actual comments: Google my name and you can easily direct an email to me, and I'll publish your comment here.

Note: Only a member of this blog may post a comment.