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From: Mike Kienenberger <mkienenb@gmail.com>
Date: Fri, 31 Jul 2015 19:13:09 -0400
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Subject: Re: java.sql.SQLException: Can't obtain connection. Request timed
 out.
To: user@cayenne.apache.org
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Ok.  Now that I've manually reduced my duplicate stack dumps so that
they're readable, I see that I do indeed have four separate threads
hitting the database at the same time, and three of them are using the
same runtime.  So apparently my app isn't as serialized as I had
previously thought.  I guess the real surprise is that it works as
well as it does with only 3 database connections in the pool.   I'll
raise that up to 5-to-10 and probably be good for another decade :)
Thanks for the hints, Andrus.


On Fri, Jun 12, 2015 at 11:21 AM, Mike Kienenberger <mkienenb@gmail.com> wrote:
> Hmm.   I just remembered that I have a second infrequently-accessed
> database which is also configured.
>
> So I'd really have 3 runtimes * 2 connection pools, so that explains 6 of the 8.
>
> Not sure where the other two are from unless I have a 4th runtime that
> I've overlooked.
>
>
> On Cayenne 4, yes, that's one of my goals this summer -- upgrade to
> Cayenne 4.  Probably won't happen until July, though.
>
>
> I'm going to add something that will dump all threads when this
> exception is hit.
>
> On Fri, Jun 12, 2015 at 11:15 AM, Andrus Adamchik
> <andrus@objectstyle.org> wrote:
>>
>>> On Jun 12, 2015, at 6:09 PM, Mike Kienenberger <mkienenb@gmail.com> wrote:
>>>
>>> And, interestingly enough, I only have 8 "PoolManagerCleanup" threads,
>>> and not the 9 that I expected.  Maybe they are create-on-demand and
>>> one of my runtimes hasn't needed it yet?
>>
>> There should be 3 actually. One per PoolManager, not one per connection. So something may be going on there.
>>
>> FWIW 4.0.M3 (master branch) has a completely new non-blocking alternative to PoolManager. The cleanup process is also more sane there.
>>
>> Andrus
>>