问题
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?
回答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.
回答2:
My jobs were still failing even after using pat's method of not using threadsafe for rake jobs.
I ended up having to use the following manual loading technique found on the GitHub Wiki page:
# file: config/initializers/custom.rb
require 'my_custom_class'
回答3:
not really related but i had today exact same error message with delayed job, without enabling threadsafe.
reason and solution was much more trivial - there was another ruby product on our server using delayed job and it's workers didnt have named queue, so they were grabbing random jobs from the queue i was setting up.
来源：https://stackoverflow.com/questions/12518529/model-classes-not-loading-in-delayed-job-when-using-threadsafe