I managed to get an outdated codebase to upgrade from Rails 2.4 / Ruby 1.8.7 to Rails 3.1 / Ruby 1.9.2. By doing this, I found a very interesting problem that took 3 days to try to figure out. I wanted to drop him here to give him some Google juice, for someone else, seeing the problem, and ask the question: Why?
Basically, I saw SystemStackErrorat the Rack level when starting my application. I could not get any requests before the error occurred, and I could not debug it because my code never touched. In development mode, I could see most of the site and then suddenly get it SystemStackErrorwhen the database was deleted. So I thought it was a lazy load.
Switch to production mode and an exception will occur on the first request. The server starts normally, but no requests occur and my code was not affected.
Fast forward too many hours, and I tracked the trace in a loop in Rails ( full text ):
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/url_for.rb:102:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_controller/metal.rb:140:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/abstract_controller/rendering.rb:74:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/abstract_controller/layouts.rb:301:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/url_for.rb:103:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_controller/metal.rb:140:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/abstract_controller/rendering.rb:74:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/abstract_controller/layouts.rb:301:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/url_for.rb:103:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_controller/metal.rb:140:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/abstract_controller/rendering.rb:74:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/abstract_controller/layouts.rb:301:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/url_for.rb:103:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_controller/metal.rb:140:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/abstract_controller/rendering.rb:74:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/abstract_controller/layouts.rb:301:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/url_for.rb:103:in `initialize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_controller/metal.rb:238:in `new'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_controller/metal.rb:238:in `block in action'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/route_set.rb:71:in `call'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/route_set.rb:71:in `dispatch'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/route_set.rb:35:in `call'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/rack-mount-0.8.3/lib/rack/mount/route_set.rb:152:in `block in call'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/rack-mount-0.8.3/lib/rack/mount/code_generation.rb:96:in `block in recognize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/rack-mount-0.8.3/lib/rack/mount/code_generation.rb:68:in `optimized_each'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/rack-mount-0.8.3/lib/rack/mount/code_generation.rb:95:in `recognize'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/rack-mount-0.8.3/lib/rack/mount/route_set.rb:141:in `call'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/actionpack-3.1.6/lib/action_dispatch/routing/route_set.rb:538:in `call'
/Users/john/.rvm/gems/ruby-1.9.2-p320@qstream-ruby19/gems/omniauth-1.1.0/lib/omniauth/builder.rb:48:in `call'
...
Here we see the cyclical nature of the system by metal.rbup url_for.rbto layouts.rbup to rendering.rbup metal.rbto url_for.rb, etc.
After considerable effort, I traced this to the next line at the top of the model file ( like this ):
include ActionView::Helpers::UrlHelpers
Please note: this is not inside the class, it is at the module level.
Interestingly, this works in Ruby 1.8.7, but calls SystemStackErrorin Ruby 1.9.2.
I created a Github repository illustrating this behavior .
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