New server, new thin, new error while executing:

Padrino/0.9.19 has taken the stage production on 3001
Thin web server (v1.2.8 codename Black Keys)
Maximum connections set to 1024
Listening on localhost:3001, CTRL+C to stop
`initialize': uninitialized constant Thin::HttpParser (NameError)
/thin-1.2.8/lib/thin/connection.rb:35:in `new'
/thin-1.2.8/lib/thin/connection.rb:35:in `post_init'
/eventmachine-0.12.10/lib/em/connection.rb:45:in `new'
/eventmachine-0.12.10/lib/em/connection.rb:36:in `instance_eval'
/eventmachine-0.12.10/lib/em/connection.rb:36:in `new'
/eventmachine-0.12.10/lib/eventmachine.rb:1430:in `event_callback'

Error occurred because there were some old (incompatible) native C extensions after OS upgrade. To fix this just reinstall Thin:

gem uninstall thin
gem install thin

If Thin version changed, you'll also need to run:

bundle install