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

[Joshua Swink]

We're using Oracle.

Josh

On Wed, Dec 16, 2009 at 8:19 PM,  <john.bush at rsmart.com> wrote:
> What db are you using? Oracle or mysql?
>
> Sent from my commodore 64
>
> 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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