[Building Sakai] How does Sakai respond to an overloaded database?

[R.P. Aditya]

On Wed, Dec 16, 2009 at 09:19:49PM -0700, john.bush at rsmart.com wrote:
> What db are you using? Oracle or mysql?

Oracle.

> On Dec 15, 2009, at 9:47 AM, "R.P. Aditya" <rpaditya at umich.edu> wrote:
> 
> >On 2009-12-09, Joshua Swink <joshua.swink at gmail.com> wrote:
> >>We had a near-outage recently when the database server got heavily
> >>loaded. We had an unprecedented number of users on Sakai. Sakai was
> >>behaving like this:
> >>
> >>- very slow page loads (up to 10 minutes)
> >>- system load factor very high (10-15)
> >>- database connection pool being exhausted (one tomcat did exhaust it
> >>and needed to be restarted; the others survived)
> >>
> >>Obviously we need to add better hardware.
> >>
> >>What I want to know is whether the application's behavior can be
> >>attributed to the user load alone, or if the database's increased
> >>response time could be responsible. One hypothesis is that the
> >>application servers would have been fine if the database had been
> >>responding in a timely fashion. Another is that the usage would have
> >>led to Sakai bogging down even if the db had been fine.
> >>
> >>Any thoughts?
> >
> >we've definitely seen this happen and typically the db connection pool
> >fills up and the appserver is unresponsive to most Sakai requests  
> >(which
> >need the db, which is most anything to do something useful) --  
> >depending
> >on the problem, adding more connection pool connections might help but
> >probably just buys you a few seconds before those extra connections  
> >are
> >eaten up, but you also increase load on the db handling extra
> >connections so unless you know that the load came from elsewhere on  
> >the
> >db server, you shouldn't exacerbate the issue from Sakai...
> >
> >Adi
> >
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