Nextcloud Internal Server Error After PHP Update

SYSTEM INFORMATION
OS type and version Ubuntu 20.04
Virtualmin version 7.1-1 Pro

I run a nextcloud 24.0.5 installation in one of my virtual servers. I just did the latest php updates, but for whatever reason my nextcloud now fails with a a completely generic internal server error:

Internal Server Error

The server encountered an internal error and was unable to complete your request.
Please contact the server administrator if this error reappears multiple times, please include the technical details below in your report.
More details can be found in the server log.

There are no errors in my apache log
There are no errors in my custom NC log
There are no errors in my the nextcloud.log file.

My test and prod servers have all the same php modules installed. Test server works, problem free… How should I go about troubleshooting this?

SOLVED

After finally finding an error I was able to determine that the php update mangled my php7.4-redis configs.

For anyone else who nextcloud throws internal errors without any errors logs… my advice is run:

systemctl (restart/status) apache2 mysql redis php*-fpm at least 20 to 30 times until you catch an error. Which is how I finally found:

● php7.4-fpm.service - The PHP 7.4 FastCGI Process Manager
     Loaded: loaded (/lib/systemd/system/php7.4-fpm.service; enabled; vendor preset: enabled)
     Active: active (running) since Fri 2022-08-26 14:57:00 CST; 40min ago
       Docs: man:php-fpm7.4(8)
    Process: 38966 ExecStartPost=/usr/lib/php/php-fpm-socket-helper install /run/php/php-fpm.sock /etc/php/7.4/fpm/pool.d/www.conf 74 (code=exited, status=0/SUCCESS)
   Main PID: 38943 (php-fpm7.4)
     Status: "Processes active: 0, idle: 2, Requests: 134, slow: 0, Traffic: 0req/sec"
      Tasks: 3 (limit: 4380)
     Memory: 32.2M
     CGroup: /system.slice/php7.4-fpm.service
             ├─38943 php-fpm: master process (/etc/php/7.4/fpm/php-fpm.conf)
             ├─38964 php-fpm: pool www
             └─38965 php-fpm: pool www

Aug 26 15:27:44 admin.example.com php[48909]:   thrown in /home/username/public_html/lib/private/Memcache/Factory.php on line 90
Aug 26 15:29:14 admin.example.com php[49083]: PHP Fatal error:  Uncaught OCP\HintException: [0]: Memcache \OC\Memcache\Redis not available for local cache (Is the >
Aug 26 15:29:14 admin.example.com php[49083]: 
Aug 26 15:29:14 admin.example.com php[49083]:   thrown in /home/username/public_html/lib/private/Memcache/Factory.php on line 90
Aug 26 15:29:35 admin.example.com php[49084]: PHP Fatal error:  Uncaught OCP\HintException: [0]: Memcache \OC\Memcache\Redis not available for local cache (Is the >
Aug 26 15:29:35 admin.example.com php[49084]: 
Aug 26 15:29:35 admin.example.com php[49084]:   thrown in /home/username/public_html/lib/private/Memcache/Factory.php on line 90
Aug 26 15:29:59 admin.example.com php[49089]: PHP Fatal error:  Uncaught OCP\HintException: [0]: Memcache \OC\Memcache\Redis not available for local cache (Is the >
Aug 26 15:29:59 admin.example.com php[49089]: 
Aug 26 15:29:59 admin.example.com php[49089]:   thrown in /home/username/public_html/lib/private/Memcache/Factory.php on line 90

After finding my error above… simply ran sudo apt-get install --reinstall php7.4-redis and grep -R "redis" /etc/php against my test server and prod server and could easily see that php-redis was misconfigured after my php update/reinstall that these files were missing on my prod server:

7.4/cgi/conf.d/20-redis.ini:extension=redis.so
7.4/fpm/conf.d/20-redis.ini:extension=redis.so
7.4/cli/conf.d/20-redis.ini:extension=redis.so

I corrected the redis config and presto everything came back.

I’ve blown a whole day of web development work… but oh well…

error logging is important. :face_with_raised_eyebrow: