Question

I’ve got an app that has been working well for a long time. I’m turning on threadsafe!, and now Delayed Job is not working, saying it can’t find one of my model files.

Job failed to load: undefined class/module Foo

This isn’t a custom job class I have defined in /lib, this is a model file in app/models

what could be causing this class to not be loaded?

Answer 1

As posted on the issue you logged, in case others find this SO post first:

I just hit this problem as well… and here’s what I found: Rails does not eager load classes if the app is loaded via a rake task (and that’s how DJ does its thing).

So what I’ve done is this snippet of code in my production.rb:

# Enable threaded mode, unless a rake task (likely Delayed Job) is running:
config.threadsafe! unless defined?($rails_rake_task) && $rails_rake_task

Rails sets that global variable when it’s loaded by a rake task. Ugly, but seems to be working for me fine now… Of course, if you have rake tasks that are multi-threaded, then this is not ideal, and you should probably invoke Rails.application.eager_load! for those tasks. I’m guessing multi-threaded rake tasks are rare though.