Alain Raap

When you run your site in debug mode, you can see where the plugins fail with deprecation errors or other php errors.
That's how we found the plugins that have problems with the new PHP version. Moodle itself runs fine on this version.

Hi Andrei,

Performance can be optimized by using caching, caching and caching, for PHP the Zend Opcache, for session and Moodle MUC Redis, for the database InnoDB (load your database in memory). It all fits together when tuned in a way that you find your bottlenecks in your Moodle stack. It took us a lot of time, but we see that every new LTS version asks for a good performance test. Redis 'untestable' means that there is no test configuration found in [your site]/admin/settings.php?section=cachestore_redis_settings, configure it there and you can run the tests. But, as Howard mentioned, it's not a really good test to find out your Redis performance. You could try the Redis benchmark on the server, but that only gives you a view of the server itself, and not when a lot of clients cache their data in Redis. There is a plugin you can install to see some stats of Redis: https://moodle.org/plugins/tool_redis
I hope this gives you a little insight, feel free to contact me if I can help you, as we run almost the same stack.

I just removed the value in the Connection timeout field on the cachestore configuration page and now
the problem seems to be solved, caching keyspace hits are back to normal. When the value is removed,

the Connection timeout is reset to 3 again, also when I change it to 0 (zero). Value 1 is saved. It's a bit

confusing how this parameter is set in Moodle when it's saved.

When I look in the muc/config.php where the cachestore is saved, I see this value, on the cachestore page itself
it shows value 3:

muc/config.php
      array (

        ....
        'compressor' => '0',
        'connectiontimeout' => 0,
        'encryption' => 0,
        ...
      ),
Cachestore page:

Redis stats: