TYPO3 Core

How did you upgrade? Are you using composer?

Thanks.

Did some expirements, and they verified my assumption from #4, its a php-executable problem:

• apache with mod_php + opcache: not affected. Update from v11.5.19 to v11.5.20 works immediately
• apache + php-fpm + without opcache: not affected. Update from v11.5.19 to v11.5.20 works immediately
• apache + php-fpm + opcache: affected. Update from v11.5.19 to v11.5.20: stays at v11.5.19 like forever (due to opcache). It errors once caches are cleared, because then TYPO3 sees v11.5.20 files, while php-fpm still executes v11.5.19 code.

So after all it's the php opcache that doesn't reevulate changing symlinks.
For nginx users this is often avoided using $realpath_root for SCRIPT_FILENAME, but that would even help here, but it still brings us to the solution. The configuration needs to teach php-fpm to always evaluate symlink paths.

So you have the following options when using apache in order to avoid this:

• Set opcache.revalidate_path=1 in the php.ini of the php-fpm environment (e.g. /etc/php/8.1/fpm/php.ini) – just found about this golden option right now, credits go to https://stackoverflow.com/a/52869752
• Call sudo systemctl reload php8.1-fpm.service after updating the symlink, in order for the php executable to clear opcache caches
• Avoid symlinks, and rather make typo3_src a directory
• (or use mod_php instead of php-fpm, but there a probably good reasons why you are using php-fpm and I'd stick to the first mentioned option)

I verified all of the above to avoid such errors after switching symlinks.

There is no codewise fix as long as we support symlink-baded installations, as it's about server configuration. We could/should add a note to the documentation somewhere.

BTW, a full backtrace would have helped to make this clear from the very beginning.
The following screenshot demonstrates the different paths being used (v11.5.20 by TYPO3 vs stale v11.5.19 by PHP-FPM):

closing issue as no feedback given anymore - guessing that it is resolved. also haven't seen any issues like that in that area.

if still relevant for you, please open a new issue and reference this one or contact me on slack