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From sebb <seb...@gmail.com>
Subject Re: doc for jdbc pool configuration
Date Mon, 04 Jan 2016 15:21:01 GMT
On 2 January 2016 at 15:38, Felix Schumacher
<felix.schumacher@internetallee.de> wrote:
> Hi all,
>
> in our documentation there is one section about the sizing of the pool,
> which I like to discuss:
>
> "If you really want to use shared pooling (why?), then set the max count to
> the same as the number of threads to ensure threads don't wait on each
> other."
>
> First: I think pooling is a valid option even for user-centric scenarios.
> Think about simulating the sql requests of an application server. In such a
> case a pool would have been used, so why not when simulating it?
>
> So for this part, I question the part "...(why?)..." and the "really" in
> front of it.

The problem is that JMeter is then mainly testing the pool
implementation rather than the server.
Since the pool implementation cannot at present be replaced, that does
not seem to be a useful approach.

> Second: When a pool is used (at least the dbcp2 pool) the connections seem
> to be stored in a stack like construct. So in a uncontended load situation
> the pool will use only a fraction of the configured size and in a contended
> situation with really many threads it will probably overload the db.

That suggests that pooling should not be used by JMeter...

> So all in all I would rather change the sentence to something like "If you
> want to use shared pooling, then set the max count to something sensible".

I think we need to document why pooling is not in general a good idea
for JMeter tests.

However I would prefer to drop pooling support entirely unless the
pool implementation can be provided by the user.

> Regards,
>  Felix

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