title: Passenger Error: The application spawner server exited unexpectedly: Unexpected end-of-file detected
body: <p>This was working just the other day, but I just updated my code to the review server which runs Passenger 2.2.4 and my 2.3.4 rails app now can't boot on that box.</p>
  
  <p>Passenger reports:</p>
  
  <pre><code>Passenger encountered the following error:
  
  The application spawner server exited unexpectedly: Unexpected end-of-file detected.
  
  Exception class:
  PhusionPassenger::Railz::ApplicationSpawner::Error
  Backtrace:
  #  File  Line  Location
  0  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/railz/application_spawner.rb  218  in `start'
  
  1  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/spawn_manager.rb  261  in `spawn_rails_application'
  
  2  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/abstract_server_collection.rb  126  in `lookup_or_add'
  
  3  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/spawn_manager.rb  255  in `spawn_rails_application'
  
  4  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/abstract_server_collection.rb  80  in `synchronize'
  
  5  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/abstract_server_collection.rb  79  in `synchronize'
  
  6  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/spawn_manager.rb  254  in `spawn_rails_application'
  
  7  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/spawn_manager.rb  153  in `spawn_application'
  
  8  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/spawn_manager.rb  286  in `handle_spawn_application'
  
  9  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/abstract_server.rb  351  in `__send__'
  
  10  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/abstract_server.rb  351  in `main_loop'
  
  11  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/lib/phusion_passenger/abstract_server.rb  195  in `start_synchronously'
  
  12  /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/bin/passenger-spawn-server  61  
  </code></pre>
  
  <p>Any ideas?</p>