How to read trace for a failed Rails migration related to Lockdown gem

Question

More often than not, when i get an error the trace will point to a line in my own code. I'll go to that line, find the error and fix it.

However, right now the trace is pointing to Rails and gem code, and I'm not sure how to use it to debug my work.

I've been following the steps listed here.

When I run rake db:migrate --trace, I get the trace shown below. I'm not asking anyone to debug it for me, but I'd appreciate any pointers to what you would look for when debugging this.

rake db:migrate --trace
(in /Users/steven/Drominay)
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
=> Mixing in Lockdown version: 1.6.2 

rake aborted!
uninitialized constant Lockdown::Frameworks::Rails::Environment::ApplicationController
/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:442:in `load_missing_constant'
/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:77:in `const_missing'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown/frameworks/rails.rb:70:in `controller_parent'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown/frameworks/rails.rb:29:in `mixin_controller'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown/frameworks/rails.rb:18:in `mixin'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown/frameworks/rails.rb:14:in `included'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown.rb:72:in `include'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown.rb:72:in `mixin_resource?'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown.rb:67:in `each'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown.rb:67:in `mixin_resource?'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown.rb:43:in `mixin'
/Library/Ruby/Gems/1.8/gems/lockdown-1.6.2/lib/lockdown.rb:85
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:155:in `require'
/Users/steven/Drominay/config/initializers/lockit.rb:1
/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:144:in `load_without_new_constant_marking'
/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:144:in `load'
/Users/steven/.gem/ruby/1.8/gems/rails-2.2.2/lib/initializer.rb:550:in `load_application_initializers'
/Users/steven/.gem/ruby/1.8/gems/rails-2.2.2/lib/initializer.rb:549:in `each'
/Users/steven/.gem/ruby/1.8/gems/rails-2.2.2/lib/initializer.rb:549:in `load_application_initializers'
/Users/steven/.gem/ruby/1.8/gems/rails-2.2.2/lib/initializer.rb:167:in `process'
/Users/steven/.gem/ruby/1.8/gems/rails-2.2.2/lib/initializer.rb:112:in `send'
/Users/steven/.gem/ruby/1.8/gems/rails-2.2.2/lib/initializer.rb:112:in `run'
/Users/steven/Drominay/config/environment.rb:14
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:153:in `require'
/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:521:in `new_constants_in'
/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:153:in `require'
/Users/steven/.gem/ruby/1.8/gems/rails-2.2.2/lib/tasks/misc.rake:3
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:607:in `invoke_prerequisites'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:604:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:604:in `invoke_prerequisites'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:596:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/bin/rake:31
/usr/bin/rake:19:in `load'
/usr/bin/rake:19

Answer 1

Fixed by changing application.rb to application_controller.rb, as per this article.

(Still interested in how to practically use this trace however.)