On 06/27/2016 12:46 PM, davepuffin via sqlalchemy wrote:
I've checked netstat and there are only 15 mysql connections (status is
still reporting the same):
Pool size: 20 Connections in pool: 19 Current Overflow: -36 Current
Checked out connections: -35
On our other servers, the number of connections (from netstat) matches
up with the pool status as expected.
I will try and recreate the problem with a test.
Many thanks!
there's almost certainly a bug on our end on that, then.
On Monday, June 27, 2016 at 4:36:21 PM UTC+1, Mike Bayer wrote:
Well it is possible QueuePool doesn't do the right thing under
eventlet,
though we use it a lot w/ eventlet in Openstack and I've tested it
myself quite a bit. Have not peeked at this number, however.
You'd need to produce for me a self contained test suite that
illustrates this behavior occurring, that would be very helpful in
order
to track this down.
Do you see too many actual database connections in play when this
condition occurs ? That is, using netstat you'd see more than 120
connections.
On 06/27/2016 11:30 AM, 'Dave Puffin' via sqlalchemy wrote:
> Thanks for the reply :)
>
> I think you're right in that it must be threading related somehow,
but
> it looks like all the monkeypatching has been applied correctly. If I
> examine the locking object used in the pool I get:
>
>>>> type(engine.pool._overflow_lock)
>
> <class 'eventlet.semaphore.Semaphore'>
>
>
> On Mon, Jun 27, 2016 at 4:21 PM, Mike Bayer
<mik...@zzzcomputing.com <javascript:>
> <mailto:mik...@zzzcomputing.com <javascript:>>> wrote:
>
>
>
> On 06/27/2016 10:48 AM, davepuffin via sqlalchemy wrote:
>
> Hi
>
> QueuePool.status() is returning some odd looking negative
values
> from
> one of our production applications.
>
> engine.pool.status()
>
> 'Pool size: 20 Connections in pool: 19 Current Overflow:
-36 Current
> Checked out connections: -35'
>
> The pool was initialised with: pool_size=20,
max_overflow=100.
>
>
> Does anyone know of any scenarios that could cause this?
>
>
> We are using SQLAlchemy==1.0.13 connecting to MySql 5.6.
> The application runs in a single python process that uses
> eventlet to
> manage many greenthreads.
>
>
>
> well that's very likely to be related, are you monkeypatching all
> thread / Lock primitives before importing SQLAlchemy? QueuePool
> relies upon traditional thread and locking primitives which will
> fail if you use them unpatched in a green-thread situation. The
> Queue here is basically Python's Queue.Queue so it appears
like the
> queue has been populated with more objects than it is supposed
to allow.
>
>
>
> The situation appears to occur sometime after the overflow
has
> been used.
>
> Thanks
>
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