[Building Sakai] Establishing new sessions are killing us during high load

[Kusnetz, Jeremy]

It seems that establishing a new Sakai session is doing some ugly things
to the database.  I'm seeing the SAKAI_PRESSENCE and SAKAI_SESSION
tables getting locked.

 

During peak times when we are getting hundreds of new sessions per
minute this is bringing the database down to it's knees.  I have to
physically break users from being able to login, and then it takes a
good 5 minutes for the database to catch up, we just see hundreds of
running mysql processes.

 

Once logins are broken, users with established sessions are running just
fine.   So we can handle users inside of Sakai just fine.

 

We tried switching the SAKAI_PRESENCE table to a memory table, that
didn't really seem to help much.

 

Just the real basics, we are using CLE 2.6.3 on top of MySQL 5.0.  This
is a clustered environment.

 

I can post more details, but just wanted to see if there are any ideas
on a quick fix here.

 

Here is an example of a locked query:

 

select
AX.SESSION_ID,AX.SESSION_SERVER,AX.SESSION_USER,AX.SESSION_IP,AX.SESSION
_HOSTNAME,AX.SESSION_USER_AGENT,AX.SESSION_START,AX.SESSION_END,AX.SESSI
ON_ACTIVE from SAKAI_SESSION AX inner join SAKAI_PRESENCE A ON
AX.SESSION_ID = A.SESSION_ID where AX.SESSION_ACTIVE=1 and A.LOCATION_ID
= x'3137343731392D70726573656E6365'

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