Upgrade from 20.0.8 to 21.0.1 kills working installation

After upgrade from 20.0.8 to 21.0.1 (which should a 20.0.9 upgrade) occ command is not usable anymore. I downloaded 21.0.1 over the existing installation. Upgrade wizard runs this time without problems, but occ still hangs at start with 100% CPU on one core, after some time the process was killed. Even at a simply ‘occ -h’ …no problem with 20.0.8

I have the exact same problem. Got a notification that 20.0.9 is available and went to update. The updater pulls in 21.0.1 (which won’t work since I am not on MySQL 8) and now my instance is stuck in maintenance mode. The OCC command gets killed.

The updater threw an error about generating indexes for the database, I believe. So might be a MySQL compatibility issue.

I found (some) workaround…
I added ‘apc.enable_cli=1’ to /etc/php/7.4/cli/conf.d/20-apcu.ini.
After that occ show an error about a missing parameter in user_ldap - I removed the app for the moment, and after that occ was usable again…one step more towards a running installation of 21.0.1 …

I have it partially running now, too. Edited the config file to disable maintenance mode. The web updater loaded again and on the second run, it did somehow manage to do the job.
However, the cron job fails to run because it can’t allocate enough memory. Temporarily switched that to AJAX to work around that one.
Also, the occ command fails to run still because of memory errors…