Rails 3 rake task can't find model in production

Question

My simple rake task, stored in lib/tasks/items_spider.rake runs just fine in development. All it does is call spider! on the Item model.

namespace :items do
  desc "Spider the web for data, hoorah"
  task :spider => :environment do
    Item.spider!
  end
end

I have the :environment task as a dependency, so everything works just fine. However, when I add RAILS_ENV=production, I hit errors, both on my local server and the production server:

$ rake items:spider RAILS_ENV=production --trace
(in /home/matchu/Websites/my-rails-app)
** Invoke items:spider (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute items:spider
rake aborted!
uninitialized constant Object::Item
/home/matchu/.rvm/gems/ruby-1.9.2-preview3@rails3/gems/rake-0.8.7/lib/rake.rb:2503:in `const_missing'
/home/matchu/.rvm/gems/ruby-1.9.2-preview3@rails3/gems/rspec-core-2.0.0.beta.22/lib/rspec/core/backward_compatibility.rb:20:in `const_missing'
/home/matchu/.rvm/gems/ruby-1.9.2-preview3@rails3/gems/rspec-expectations-2.0.0.beta.22/lib/rspec/expectations/backward_compatibility.rb:6:in `const_missing'
/home/matchu/Websites/openneo-impress-items/lib/tasks/items_spider.rake:4:in `block (2 levels) in <top (required)>'
/home/matchu/.rvm/gems/ruby-1.9.2-preview3@rails3/gems/rake-0.8.7/lib/rake.rb:636:in `call'
[...trace of how rake gets to my task...]

This just seems odd to me. Apparently the models have not been loaded correctly. I'm on Rails 3.0.3, though development on this app started back when Rails 3 was in beta. How can I go about debugging this issue? Thanks!

Answer 1

Contrary to running your application in production, a Rake task does not eager load your entire code base. You can see it in the source:

module Rails
  class Application
    module Finisher
      # ...
      initializer :eager_load! do
        if config.cache_classes && !$rails_rake_task
          ActiveSupport.run_load_hooks(:before_eager_load, self)
          eager_load!
        end
      end
      # ...
    end
  end
end

So only if $rails_rake_task is false, will the application be eager-loaded in production. And $rails_rake_task is set to true in the :environment Rake task.

The easiest workaround is to simply require the model that you need. However, if you really need all of your application to be loaded in the Rake task, it is quite simple to load it:

Rails.application.eager_load!

The reason all of this work in development is because Rails autoloads your models in development mode. This also works from within a Rake task.