It's only created when something is actually logged. We're actually not too big on logging and usually only logging when something goes wrong.

Maybe put a line like \Piwik\Log::info('foo bar'); into core/FrontController.php in the dispatch method around line 150. Maybe something appears then?

Thank you @tsteur for you answer.

I followed your instructions and I navigated on the UI but unfortunately without result
I don't have any log.

I am not entirely sure if this isn't a bug in Matomo.
I am just setting up a new Matomo instance and no matomo.log file is created.

Maybe this is a regression from one of the recent logging changes

I can reproduce it when the screen writer is not enabled. If the screen writer is enabled too, then it works.

Actually I can't reproduce it. I had a mistake in the config file. Tested various cases with and without instanceId etc.

Maybe only happens with some specific PHP version or so. The file that does it is vendor/monolog/monolog/src/Monolog/Handler/StreamHandler.php and plugins/Monolog/Handler/FileHandler.php.

I doubt we can do much on our side here. If someone could debug this, that would be great. We may have a look if someone can provide access to a server and Matomo where this can be reproduced. Make otherwise sure the config section isn't defined twice etc.

@floSoX
This should be fixed with #14296 (and therefore the next Matomo release)

For me manually applying https://patch-diff.githubusercontent.com/raw/matomo-org/matomo/pull/14296.patch does fix the issue (you can ignore the change in tests/PHPUnit/Fixtures/UITestFixture.php)

(thanks to @diosmosis for the tip)

@Findus23

I still have this issue with Matomo v3.9.1. PHP version I am using is php 7.2 by red had software collections.

I am going to try to apply the patch manually.

The patch actually solves the problem. Should be applied in next Matomo version.