First, your content here for Nextcloud has been excellent and educational.  Worth our time.

I'm running an instance of Nextcloud and trying to on-board about 100+ users for my non-profit office.  Our setup is a physical server with 3 Virtual Servers running Ubuntu.  One is an iRedMail server running OpenLDAP, another is the Nextcloud server, and the third is a Collabora server.  I'm using the LDAP app to authenticate with Nextcloud.  All of these things are realatively working fine.  But infrequently we are experiencing times where the web service is grinding to a halt.  I've never tried to wait it out and see if it resolves the issue on its own.  I do not see anything in the Nextcloud log to indicate an issue.  The htop monitor doesn't show any resource being taxed and network traffic doesn't seem hampered.  So I initially started disabling all of the apps that were third party but that didn't seem to help.  Then I noticed when I disable the Talk app, it seems to recover instantly.  I can then enable it again and the server will respond fine for sometimes a couple weeks, but sometimes only a couple hours.  I will see errors popping up in Talk where it is trying to load an ongoing thread and will fuss about not being able to join the conversation or find the members of it.

At this point I'm wondering if there is something happening with all of the LDAP lookups.  I just don't know where else to keep looking.  Any thought or ideas are welcome.

Our setup is Ubuntu 20.04, PHP 7.4.3, Apache and MySQL are up to date, Nextcloud is 25.0.6. 

Hi Matt, welcome to the forum. I've got less experience on the LDAP side of things. Does iRedMail or OpenLDAP have a log you can watch to see what lookups are being made from Nextcloud when or after it freezes? I would definitely check Apache's error.log and access.log if you haven't already (they're in /var/log/apache2/ by default.) What percentage of CPU time does htop or top show that apache2 is using when this issue occurs? Does restarting Apache (or the entire Nextcloud VM) do anything when it's frozen?

I've noticed my own Nextcloud servers have started warning me that I should upgrade to PHP 8. I'm on Debian stable, which is still stuck on 7, but since you're using Ubuntu, I would suggest upgrading at least the VM running Nextcloud to Ubuntu 22.04 LTS so you can get PHP 8.1, just in case it makes a difference.

People on the Nextcloud community forum may have more ideas: https://help.nextcloud.com/

Thank you for the reponse.  I'm also tracking a couple other possible solutions.  One is that it is recommended to run ACPu locally for the memcache instead of Redis so I switched that for local and haven't had an issue yet.  Also, I am adjusting my settings for mysql to allow more ram usage.  I should note that I bumped the max memory limit of PHP to 2GB.  That is where the memory sits all day.  Just right at 2.25.  It doesn't go past that and it rarely goes below that.

As for PHP 8.1, everytime I try to upgrade on my test server, either by just upgrading to 8.1 or upgrading the Ubuntu to 22, it causes the server to crash and I haven't found a way to fix what is missing.  Do you perhaps have a video on this?   I did build a test maching from 22.04 natively and it works but I am not having success with a simple upgrade.

Glad to hear switching the memcache out might have helped.

With regards to upgrading from 20.04 to 22.04 (there is no "22," as 22.04 and 22.10 are separate versions), I have an older video that covers Ubuntu release upgrades in general, including both the Ubuntu-suggested automatic way and a more manual way that works on Debian and Ubuntu: https://nerdonthestreet.com/episode/tech/upgrading-to-ubuntu-20-04-lts

You'd have to be more specific about what "server crashing" means in that context. How would you have upgraded to PHP 8.1 without upgrading Ubuntu? Is it Apache or Nextcloud that's crashing, or the entire OS?

I'd have to run through it again to verify the details but as I recall, the Nextcloud instance just returns with an Internal Server Error message.  I've followed steps to add the repo for PHP8 to the Ubuntu 20 and toggled to selecting the 8.1 version but that doesn't work nor the OS upgrade.  I believe that all needed packages are not installed natively, plus the newly installed ini files would have to be tweaked like the previous files but after performing those steps it seems that I'm still missing something.  I will check the video an also use a snapshot copy so I can revert if things don't work for me.  I cannot believe they are already running the NC 27 Beta now and I just upgraded to 25.  I do however thank you for your time in checking in with me and the work you have put into your videos.  I've learned a lot!