Error H13 (Connection Closed without response) Heroku

Question

I am working on Ruby on Rails. A project which works fine on local server and when I deploy it on heroku it gives following error. Thanks!

2012-06-12T14:19:23+00:00 heroku[router]: Error H13 (Connection closed without response) -> GET sheets-vip.heroku.com/ dyno=web.1 queue= wait= service= status=503 bytes=
2012-06-12T14:19:23+00:00 heroku[nginx]: 122.179.134.45 - - [12/Jun/2012:14:19:23 +0000] "GET / HTTP/1.1" 503 601 "-" "Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20100101 Firefox/12.0" myapp1101.heroku.com
2012-06-12T14:27:35+00:00 app[web.1]: !! Unexpected error while processing request: can't modify frozen array
2012-06-12T14:27:35+00:00 heroku[router]: Error H13 (Connection closed without response) -> GET sheets-vip.heroku.com/ dyno=web.1 queue= wait= service= status=503 bytes=
2012-06-12T14:27:35+00:00 heroku[nginx]: 122.179.134.45 - - [12/Jun/2012:14:27:35 +0000] "GET / HTTP/1.1" 503 601 "-" "Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20100101 Firefox/12.0" myapp1101.heroku.com

Answer 1

This error occurs when something deep down in a dependency of your app blows up. For instance, we saw this error when an incoming request was enormous (i.e. it was a JSON document at +100K). We were able to fix this by setting:

Rack::Utils.key_space_limit = some appropriate value

That is, the H13 was b/c of a Rack error. Try increasing logging in your application as that might point to the error (that's how we ultimately zeroed in on the Rack key space limit).