Error Deploying to Production on Heroku

I have been making progress with a personal application that I am working on.  In the early days of development, I had deployed a version of the application to Heroku - and it worked fine at that time.  Fast forward 6 months or so and lots of changes.  I deployed to Heroku and received an error when trying to view the website:

heroku logs
2014-12-25T01:17:54.017424+00:00 heroku[web.1]: State changed from starting to crashed
2014-12-25T01:17:55.195360+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=example.herokuapp.com request_id=0c587d48-ac93-4bce-91bc-9d2de62e6a86 fwd="73.53.247.100" dyno= connect= service= status=503 bytes=
2014-12-25T01:17:55.719076+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=example.herokuapp.com request_id=d586d82a-8c27-4f57-b5f1-cf2b55c155d7 fwd="73.53.247.100" dyno= connect= service= status=503 bytes=

That error made no sense to me.  What the heck, I know the favicon.ico file exists, and why can't I get to the root path?  So I went to the rails console via heroku:

heroku run rails console
Running `rails console` attached to terminal... up, run.9397
/app/app/models/connexion.rb:1:in `<top (required)>': superclass mismatch for class Nurny (TypeError)
  from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:247:in `require'
  from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.7/lib/active_support/dependencies.rb:247:in `block in require'

Note that I am substituting my real class name with a bogus one, 'Nurny', for this example.

Ok, now I get an error that looks like a real error, though I didn't understand it.  Luckily this all occurred the night before our weekly morning Code and Coffee.  So I brought the issue up and Micah gave me a hand for a while, having me try different things.

The conflict only shows when trying to run in a production environment.  I had a model for 'Nurny' that had a class defined of Nurny.  However, I also have a model concern, for queries, with a class of 'Nurny' which was the cause of the issue.

So, now how can I fix this?  I tried a simple rename of the concern, changing the line:

BEFORE
class Nurny

AFTER
class NurnyQry

But that spurred a flurry of new problems.  Luckily I found another solution while thinking through this issue.  Why did the app work fine in a development rails environment, but not in production.  Now I must confess I'm not sure if my solution will have a profound negative effect, but so far I have not encountered any issues.  The solution lies in the config/environments/production.rb file:

BEFORE:
config.eager_load = true<

AFTER:
config.eager_load = false

And that simple configuration change fixed my issue!

Learn Something New Every Day

Last Edited by: John on November 11, 2015