I am getting a couple different errors at a particular line of code in one of my models when running in Sidekiq-queued jobs. The code in question is:
@lookup_fields[:asin] ||= self.book_lookups.find_by_name("asin").try(:value)
I either get undefined method 'scope' for #<ActiveRecord::Associations::AssociationScope:0x00000005f20cb0> or undefined method 'aliased_table_for' for #<ActiveRecord::Associations::AliasTracker:0x00000005bc3f90>.
At another line of code in another Sidekiq job, I get the error undefined method 'decrypt_and_verify' for #<ActiveSupport::MessageEncryptor:0x00000007143208>.
All of these errors make no sense, as they are standard methods of the Rails runtime support libraries.
The model in question has a :has_many association defined for the "book_lookups" model, "name" and "value" are fields in the "book_lookups" model. This always happens on the first 1-3 records processed. If I run the same code outside of a Sidekiq job, these errors do not occur.
I cannot reproduce the error on my development machine, only on production which is hosted at Heroku.
I may have "solved" the first set of errors by putting the code `BookLookup.new()' in an initializer, forcing the model to load before Sidekiq creates any threads. Only one night's work to go on, so we'll have to see if the trend continues...
Even if this solves the immediate problem, I don't think it solves the real underlying issue, which is classes not getting fully loaded before being used. Is class-loading an atomic operation? Is it possible for one thread to start loading a class and another to start using the class before it is fully loaded?
I believe that I have discovered the answer: config.threadsafe!, which I had not done. I have now done that and most if not all of the errors have disappeared. References: http://guides.rubyonrails.org/configuring.html, http://m.onkey.org/thread-safety-for-your-rails (especially the section "Ruby's require is not atomic").