I followed the guide described here https://devcenter.heroku.com/articles/logging#creating-your-own-syslog-drain to create my own rsyslog drain.
I configured my rsyslog with the following line:
:inputname, isequal, "imtcp" /var/log/heroku.log
That only worked after I updated my rsyslog from 5.x to 7.x. A bug was preventing rsyslog to use the port 514. But after the update it worked fine.
But now I want to split the logs one file per application. I found another question about that saying that I should use:
if $hostname isqual "d.123..." then /var/log/my_application.log
Where "d.123..." is the actual drain ID that Heroku provides. But that didn't work. I tried several variations following the docs on rsyslog site. None worked.
Again, using one single file worked. Every app on Heroku I configured to use that drain has successfully sent its log to it. But it seems that I can't find out how to split files one per application.
Thanks in advance.
JUST found out that you have to manually create the log files. rsyslog can't create them and doesn't complain in its own log.
So, I used the configuration proposed in the article and ran touch my-application-123.log plus chown syslog:adm my-application-123.log then it worked.