Hi every one,
We are using PostgreSQL and having some issues while servers are under heavy traffic, the data base server fills all connection slots with a lot of "SELECT ... waiting..", i think that is related to the pg_advisory_lock() because these are queries waiting for the session lock. (wich is strange unless a lot of users were opening multiple tabs all time...)
It seems that reducing the time Moodle waits to get the session lock (SESSION_ACQUIRE_LOCK_TIMEOUT) on config.php has solved the problem for now. Default value for this parameter tells moodle to wait 2 min until raise timeout to the browser. We set the parameter value to 30s wich is by far enough response time to a fully functional website. This avoid stacking of connections to the database waiting for session lock.
I keep testing and looking for more information about why exactly this happened.
Any feedback is welcome!
Thaks and sorry for my english
P.S: We have a multi-portal centraliced moodle installation with about 25.000 users and 4.000 active courses, but on moodle2.3 we have 17.500 active users and 1.000 active courses
by Alberto Lorenzo Pulido.