Re: [Sqlalchemy-users] SQLAlchemy and locking up.

Sun, 25 Jun 2006 22:56:10 -0700

you should try 1657 to see if it solves your problems right now.  I am also posting on the Python list to see what they think of formally allowing the Lock to be configurable, or at least making it an RLock (someone else also wanted this feature :  http://mail.python.org/pipermail/python-list/2006-April/336948.html ).

if they think that doing Queue operations inside of __del__() is "incorrect", then I will probably have to just copy Queue.Queue's internals into a simplified version and just make them intrinsic to QueuePool.  Queue is a very simple class.

this is why I roll my own libraries for this kind of thing usually....cant trust anything out there !

On Jun 26, 2006, at 1:31 AM, Dennis Muhlestein wrote:



On 6/25/06, Michael Bayer <[EMAIL PROTECTED]> wrote:
Actually, closer inspection of the stack trace reveals something
interesting:  there is one thread where the __del__ method on the
ConnectionFairy is getting called within the get() method of Queue,
and creating a reentrant lockup since __del__ tries to return the
connection to the Pool, calls put() on Queue, and the mutex is
already grabbed by the enclosing get().

Changeset 1657 commits some initialization to change Queue's mutex to
be a threading.RLock, and the two threading.Conditions to derive from
it, so that a put() wtihin a get() wont hang within a single thread.

I think this might be the actual thing going on, although i cannot
reproduce a __del__ getting called just like that.  i think 1657
might solve your problem.

this also might be a cue to start thinking about not using
Queue.Queue for the connection pool, since im never a fan of changing
internals like that.


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