As i say in the title, the app produces a 500 internal server error, but in the logs there isn't the error, so I don't know how to understand what is happening.
This is the log:
2015-11-30T16:31:50.881209+00:00 heroku[router]: at=info method=GET path="/" host=myapp.herokuapp.com request_id=52d75ec4-3345-4d3c-88e6-a5f08c366dc2 fwd="151.77.121.140" dyno=web.1 connect=0ms service=10ms status=500 bytes=765
2015-11-30T16:31:50.882326+00:00 app[web.1]: 10.76.13.112 - - [30/Nov/2015:16:31:50 +0000] "GET / HTTP/1.1" 500 495 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36
2015-11-30T16:31:51.618891+00:00 app[web.1]: 10.76.13.112 - - [30/Nov/2015:16:31:51 +0000] "GET /favicon.ico HTTP/1.1" 200 5430 "https://myapp.herokuapp.com/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36
2015-11-30T16:31:51.617820+00:00 heroku[router]: at=info method=GET path="/favicon.ico" host=myapp.herokuapp.com request_id=cf2ecf03-65ee-4213-8d52-a7eaaa24ac76 fwd="151.77.121.140" dyno=web.1 connect=0ms service=1ms status=200 bytes=5696
How can I know which kind of error is producing the app so I can fix it?
Solved. To see the errors produced by the application, Symfony has to be configured to be compatible with the ephemeral system that Heroku uses.
So in config_prod.yml set the monolog to write to php://stderr:
monolog:
handlers:
main:
type: fingers_crossed
action_level: error
handler: nested
nested:
type: stream
# Required by Heroku ephemeral filesystem
path: "php://stderr"
level: debug
console:
type: console
More info about how to configure logging for Symfony apps on Heroku can be found on their help pages.
PS
The error was a simple mispelling: wrote default/index.html.twig instead of Default/index.html.twig. Is a problem of capital letters and git commits. Very simple but so tedious and hard to find!