We are currently using memcache as application cache and once in a while the configuration seems to be cleared.
The MUC settings seems to be set back to default. This thing has happened two times the last month and it occured sometime around midnight both times.
Apparently you need one instance of Memcache for the MUC cache and another instance of Memcache for the Moodle session management. Is that how you've set it up?
https://docs.moodle.org/27/en/Session_handling#Memcached
https://docs.moodle.org/27/en/Caching#Memcached
Ok, those articles are for Memcached, but the setup is probably similar.
Actually we have our sessions stored in DB (default). We have never seen any performance-problems related to that so for that reason we have kept sessions in DB.
The problem in this case is that the Memcache instance configuration is flushed for some reason so I have to add the memcache instance again. As you can see below memcache store has disappeared. This happens at least once per day now. I can see that the muc/config.php is set back to default
I've also seen this happen several times, the MUC memcache settings would be entered only to be reset to the defaults (file-based) a few hours later. What version of moodle are you running? Is your moodledata directory on shared storage or local disk?
Ok, nice to hear that we are not alone
Yes our moodledata directory is on a shared storage (NFS share). Localcachedir and tempdir resides on local filesystem though (not that it should matter).
We did upgrade our moodle platform earlier this summer to 2.8.5+ and at the same time we changed our memcache store to a memcached store instead. However the problem is still there with the muc/config.php being reset now and then.
In some certain situation moodle decides to reset the muc settings. I haven't figured out yet what could be triggering this strange behaviour.
