My Heroku-hosted (ruby Sinatra) app has worked perfectly for the last month without me changing it, but today the app error'd while trying to start up after idling:
2013-02-08T15:44:34+00:00 heroku[web.1]: Idling
2013-02-08T15:44:38+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2013-02-08T15:44:40+00:00 heroku[web.1]: Process exited with status 0
2013-02-08T15:44:40+00:00 heroku[web.1]: State changed from up to down
2013-02-08T15:50:50+00:00 heroku[web.1]: Unidling
2013-02-08T15:50:50+00:00 heroku[web.1]: State changed from down to starting
2013-02-08T15:52:09+00:00 heroku[router]: at=error code=H20 desc="App boot timeout" method=GET path=/ host=www.example.com fwd=207.110.13.98 dyno= queue= wait= connect= service= status=503 bytes=
2013-02-08T15:52:05+00:00 heroku[router]: at=error code=H20 desc="App boot timeout" method=GET path=/ host=www.example.com fwd=207.110.13.98 dyno= queue= wait= connect= service= status=503 bytes=
After a few more minutes of error codes, the app tried to unidle again and did so successfully. Any idea what caused this and how I could prevent it from happening again?