On Aug 4, 2006, at 10:06 PM, Tzahi Fadida wrote:
> Anyway, if i believe there is a bug i am reporting it in case other
> bugs follows.
>
> I have tried what you described with and without threadlocal, and with
> explicitly deleting every object i can find, like the transaction,
> session
> etc... and it does not release the connections.
you should show me a test program that illustrates this. keep in
mind that __del__() is not guaranteed to be called immediately, and
sleeping threads is also no guarantee. while the connection proxy
that you get from a pool is constructed without circular references
and has very good __del__() behavior in cPython, the
SessionTransaction is not meant for that kind of usage so it hasnt
been optimized for that.
oftentimes you have to wait for the garbage collector to come
around. so heres my test, which works fine:
>>> from sqlalchemy import *
>>> e = create_engine('sqlite://', echo_pool=True)
>>> s = create_session(bind_to=e)
>>> t = s.create_transaction()
>>> c = t.connection(None)
[2006-08-05 09:38:15,242] [pool] : Connection
<pysqlite2.dbapi2.Connection object at 0x1059980> checked out from pool
>>> c = None
>>> t = None
>>> s = None
>>> import gc
>>> gc.collect()
[2006-08-05 09:38:28,452] [pool] : Connection
<pysqlite2.dbapi2.Connection object at 0x1059980> being returned to pool
28
>
> Btw:
> The db engine,mapping,metadata are defined and exists persistently
> outside the
> threads. Sessions and transactions are created inside threads.
> The threads are destroyed immediately after transaction creation
> (and running
> a little select query as i described in previous mails).
> Also, just to be on the safe side :), one thread is sleeping for 60
> secs and
> then try to repeat the transaction creation etc... just to make
> sure if
> SQLAlchemy needs to do anything active to release the connection.
>
> On Saturday 05 August 2006 03:47, Michael Bayer wrote:
>> actually, all connections that are freed by the pool have a rollback
>> () called on them automatically.
>>
>> also, connections are returned to the pool when the proxying object
>> of the connection has its __del__ method called, so the behavior you
>> want is already there. if you lose all references to a
>> SessionTransaction as well as the Session its associated with, when
>> they get garbage collected, so will all connections theyre holding
>> onto, and the connection will be returned to the pool (and the
>> rollback() will be performed). assuming your engine is not using the
>> "threadlocal" strategy.
>>
>> if you are using the "threadlocal" strategy, not as simple; the
>> engine is holding on to the current transaction associated with the
>> current thread; its by design that you dont have to hold on to any
>> transactional object, and the transaction remains open, until
>> explicitly committed or rolled back (which can be performed directly
>> off the engine in the case of 'threadlocal').
>>
>> if you want very explicit management of resources, not using
>> "threadlocal" for your create_engine() strategy, using "default"
>> instead, is the first step.
>>
>> also, even though the functionality you want is present, it strikes
>> me as a poor practice to use a SessionTransaction without a try:/
>> finally: block that explicitly calls rollback() or commit() on it.
>> I cant think of a reason youd want to begin a transaction and then
>> just let it fall away without managing its closure; it seems to
>> defeat the purpose of a transaction, which is, demarcation of a set
>> of operations.
>
> --
> Regards,
> Tzahi.
> --
> Tzahi Fadida
> Blog: http://tzahi.blogsite.org | Home Site: http://tzahi.webhop.info
> WARNING TO SPAMMERS: see at
> http://members.lycos.co.uk/my2nis/spamwarning.html
>
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