H10 - App 崩溃了

Web dyno 上的崩溃的 web dyno 或启动超时将显示此错误。

2010-10-06T21:51:04-07:00 heroku[web.1]: State changed from down to starting
2010-10-06T21:51:07-07:00 app[web.1]: Starting process with command: `bundle exec rails server -p 22020`
2010-10-06T21:51:09-07:00 app[web.1]: >> Using rails adapter
2010-10-06T21:51:09-07:00 app[web.1]: Missing the Rails 2.3.5 gem. Please `gem install -v=2.3.5 rails`, update your RAILS_GEM_VERSION setting in config/environment.rb for the Rails version you do have installed, or comment out RAILS_GEM_VERSION to use the latest version installed.
2010-10-06T21:51:10-07:00 heroku[web.1]: Process exited
2010-10-06T21:51:12-07:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=myapp.herokuapp.com fwd=17.17.17.17 dyno= connect= service= status=503 bytes=