well, if your app has SessionTransactions lying around that dont have
an explicit commit() or rollback(), thats a situation that should be
corrected in your application. gc.collect() is a heavy operation
best managed by the python interpreter in normal circumstances.
On Aug 5, 2006, at 10:30 AM, Tzahi Fadida wrote:
> OK, if i use gc.collect() it is released.
> Though i was very surprised that collect() takes so much time.
> I wonder if it is reasonable to gc.collect() after each thread ends
> or at least when the pool manager thinks the rope is getting too
> short.
>
> On Saturday 05 August 2006 16:46, Michael Bayer wrote:
>> 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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>
> --
> Regards,
> Tzahi.
> --
> Tzahi Fadida
> Blog: http://tzahi.blogsite.org | Home Site: http://tzahi.webhop.info
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