Question

I can’t seem to use a simple rack middleware with Rails 3.1 (rc4). Is something missing? Here’s how I built my app:

$ rails new skel192 -G -O -T

I add this line at the end of Gemfile:

gem 'rack-contrib'

I add these lines to config/application.rb:

require 'rack/contrib'
...
config.middleware.use Rack::NotFound.new('public/404.html')

[NOTE: I’m not really planning to use RackNotFound, I was trying to use the simplest middleware I could think of.]

Then for good measure:

$ bundle install
...
$ bundle update
...

FYI:

$ ruby -v
ruby 1.9.2p290 (2011-07-09) [i386-mingw32]
$ rails -v
Rails 3.1.0.rc4

But when I run:

$ rails server
=> Booting WEBrick
=> Rails 3.1.0.rc4 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
Exiting
C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.1.0.rc4/lib/active_support/inflector/methods.rb:124:in `const_defined?': wrong constant name #<Rack (NameError)
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.1.0.rc4/lib/active_support/inflector/methods.rb:124:in `block in constantize'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.1.0.rc4/lib/active_support/inflector/methods.rb:123:in `each'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.1.0.rc4/lib/active_support/inflector/methods.rb:123:in `constantize'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.1.0.rc4/lib/active_support/dependencies.rb:527:in `block in initialize'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.1.0.rc4/lib/active_support/dependencies.rb:549:in `yield'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.1.0.rc4/lib/active_support/dependencies.rb:549:in `default'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.1.0.rc4/lib/active_support/dependencies.rb:549:in `[]'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.0.rc4/lib/action_dispatch/middleware/stack.rb:24:in `klass'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.0.rc4/lib/action_dispatch/middleware/stack.rb:43:in `build'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.0.rc4/lib/action_dispatch/middleware/stack.rb:112:in `block in build'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.0.rc4/lib/action_dispatch/middleware/stack.rb:112:in `each'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.0.rc4/lib/action_dispatch/middleware/stack.rb:112:in `inject'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.0.rc4/lib/action_dispatch/middleware/stack.rb:112:in `build'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/engine.rb:429:in `app'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/application/finisher.rb:37:in `block in <module:Finisher>'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/initializable.rb:25:in `instance_exec'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/initializable.rb:25:in `run'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/initializable.rb:50:in `block in run_initializers'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/initializable.rb:49:in `each'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/initializable.rb:49:in `run_initializers'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/application.rb:96:in `initialize!'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/railtie/configurable.rb:30:in `method_missing'
        from C:/work/tech/external/lb/skel192/config/environment.rb:5:in `<top (required)>'
        from C:/work/tech/external/lb/skel192/config.ru:4:in `require'
        from C:/work/tech/external/lb/skel192/config.ru:4:in `block in <main>'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/builder.rb:51:in `instance_eval'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/builder.rb:51:in `initialize'
        from C:/work/tech/external/lb/skel192/config.ru:1:in `new'
        from C:/work/tech/external/lb/skel192/config.ru:1:in `<main>'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/builder.rb:40:in `eval'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/builder.rb:40:in `parse_file'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/server.rb:200:in `app'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/commands/server.rb:46:in `app'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/server.rb:301:in `wrapped_app'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/server.rb:252:in `start'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/commands/server.rb:70:in `start'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/commands.rb:54:in `block in <top (required)>'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/commands.rb:49:in `tap'
        from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.0.rc4/lib/rails/commands.rb:49:in `<top (required)>'
        from script/rails:6:in `require'
        from script/rails:6:in `<main>'

Am I missing something?

Answer 1

I’m still not sure why Rack::NotFound and other rack-contrib middlewares are failing with Rails 3.1 but I did learn something else:

Sinatra 1.2.x does not play well with Rails 3.1. Switching to Sinatra 1.3.0.e eliminated some other problems I was experiencing with my own middlewares.

To install:

$ [sudo] gem install sinatra --prerelease

Then update your middlewares’ dependencies.