logging: Allow logging to web server error_log

[jtojnar]

This PR adds a new configuration option logger_destination allowing to choose between Monolog’s ErrorLogHandler and StreamHandler.

[jtojnar]

I am actually not sure if there is any benefit of using error_log compared to file:php://stderr.

[jtojnar]

It looks like the behaviour is slightly different on different servers, however, both go through stderr to server’s error log (SAPI error log).

Apache httpd

Both are written to httpd error log:

• error_log function: [Wed Dec 06 02:12:51.537817 2017] [php7:notice] [pid 20094] [client ::1:49470] [2017-12-06 02:12:51] selfoss.DEBUG: Establish database connection \n
• stderr: [2017-12-06 02:25:33] selfoss.DEBUG: Establish database connection

nginx + php-fpm

Both are written to php-fpm pool error log (system journal in my case)

• error_log function: Dec 06 03:18:45 srv php-fpm[328]: [WARNING] [pool reader] child 26568 said into stderr: "NOTICE: PHP message: [2017-12-06 03:18:45] selfoss.DEBUG: Establish database connection "
• stderr: Dec 06 03:20:43 srv php-fpm[328]: [WARNING] [pool reader] child 26568 said into stderr: "[2017-12-06 03:20:43] selfoss.DEBUG: Establish database connection "

It looks like using stderr leads to more concise logs.

Edit: It looks like php-fpm discards stderr by default (see catch_workers_output) so the error_log option is useful after all.

[jantman]

I haven't tested this yet but it looks absolutely wonderful for people like me who are trying to run selfoss in Docker and have existing log management being done at the docker level. This makes it much easier to run selfoss like a proper 12 factor app.

Thanks so much!