Rails 3 + Passenger: Rack error

Question

I'm getting the following error, which spontaneously popped up and crashed my site a few days ago. I'm using Ruby 1.8.7, Rails 3.0.0, on a Dreamhost machine with Passenger. See this cached page for another description of the same problem.

Ruby (Rack) application could not be started.

A source file that the application requires, is missing.

It is possible that you didn't upload your application files correctly. Please check whether all your application files are uploaded.
A required library may not installed. Please install all libraries that this application requires.

Error message:
no such file to load -- rack
Exception class:
LoadError
Application root:
[omitted]
Backtrace:
#   File    Line    Location
0   /usr/lib/ruby/1.8/rubygems/custom_require.rb    31  in `gem_original_require'
1   /usr/lib/ruby/1.8/rubygems/custom_require.rb    31  in `require'
2   /dh/passenger/lib/phusion_passenger/rack/application_spawner.rb 139 in `load_rack_app'
3   /dh/passenger/lib/phusion_passenger/rack/application_spawner.rb 100 in `run'
4   /dh/passenger/lib/phusion_passenger/utils.rb    255 in `report_app_init_status'
5   /dh/passenger/lib/phusion_passenger/rack/application_spawner.rb 87  in `run'
6   /dh/passenger/lib/phusion_passenger/rack/application_spawner.rb 65  in `spawn_application'
7   /dh/passenger/lib/phusion_passenger/utils.rb    184 in `safe_fork'
8   /dh/passenger/lib/phusion_passenger/rack/application_spawner.rb 58  in `spawn_application'
9   /dh/passenger/lib/phusion_passenger/rack/application_spawner.rb 41  in `spawn_application'
10  /dh/passenger/lib/phusion_passenger/spawn_manager.rb    159 in `spawn_application'
11  /dh/passenger/lib/phusion_passenger/spawn_manager.rb    287 in `handle_spawn_application'
12  /dh/passenger/lib/phusion_passenger/abstract_server.rb  352 in `__send__'
13  /dh/passenger/lib/phusion_passenger/abstract_server.rb  352 in `main_loop'
14  /dh/passenger/lib/phusion_passenger/abstract_server.rb  196 in `start_synchronously'
15  /dh/passenger/bin/passenger-spawn-server    61  

Answer 1

I also had the same problem with Dreamhost/Passenger/Rails. I send a support request in and received the following response. My sites are also now up and running.

---

Thank you for contacting technical support. I do apologize for the issues with this. The servers were upgraded to Debian recently which also did some upgrades regarding your install. I went ahead and corrected the sites with errors as some gems needed to be reinstalled.

I do apologize for the issues with this. Please let me know if there is anything else I can do for you and have a good day.

Answer 2

I had to go through the same path. After filing a support ticket app got back on track:

Thank you for contacting technical support. I do apologize for the issues with your site. It looks like there was an issue with your rack Gem. I went ahead and reinstalled the Gem for you and then rebundled your Rails application. Your site is now back up and running. :) I do see that your images are not loading though. Doing some research into this, I see that the files do not exist in your assets folder. You will need to look into this and get the files uploaded to resolve this issue. :)

Please let me know if there is anything else I can do for you and have a great day.

The image problem was not related to this.

Answer 3

I experienced the same problem, it had to do with bundling my gems together correctly. The server was looking for required gems at /usr/lib/ruby/gems/1.8/ . Rerunning bundle install on the server corrected my problems. Hopefully this will help someone else, as this problem seems to have many causes.