I would like to have your opinion about a problem we had recently in our production server. We use moodle since 2006 and we've never had anything similar before.
We have a full agenda of online exams this week (and last week), moodle was responding pretty well, kind of slow in some occasions (simultaneous logins and maybe due to some network issues)... but in general doing a great job, as usual. At the end of a busy day Moodle started to get really really slow, we started to get database error messages in the browser and we couldn't even login.
App servers load was ok, but monitoring slow queries we could see "select * from mdl_sessions;" every 2, 3 seconds. This table had about 7000 records. Restarting database didn't solve the problem. Only restarting apache solved it.
We don't understand yet what happened. Has anyone experienced something similar? Your opinion is very welcome.
2 app servers (load balancing)
1 db server