[ZODB-Dev] Threads and Connections

[Chris S]

The problem is the only objects I need to grab are the ones loaded by
other connections. I use Python's garbage collector to track
references to instances of classes that have been updated. Aside from
the strange error below, the live update functions correctly. It's
almost like the connection is keeping a special cache that's
conflicting with the new objects.

Chris

On 7/25/06, Mika, David P (GE, Research) <mika at crd.ge.com> wrote:
> I don't know the answer to your question, but when I have separate threads,
> I always have each thread independently control their own connection
> (open and close).  Perhaps in your situation, you could have the
> update function open it's own connection, grab the object in question
> from the ZODB, change it, commit it and close.
> Dave
>
> -----Original Message-----
> From: zodb-dev-bounces+mika=research.ge.com at zope.org
> [mailto:zodb-dev-bounces+mika=research.ge.com at zope.org]On Behalf Of
> Chris S
> Sent: Friday, July 21, 2006 6:29 PM
> To: zodb-dev at zope.org
> Subject: [ZODB-Dev] Threads and Connections
>
>
> Is it possible to close a connection used in one thread from another
> thread? My program has a locking mechanism, so I can ensure threads
> don't use their connection while it's closed, but whenever I try to
> close one thread's connection from another thread, I get errors like:
>
>     self.conn.close()
>   File "C:\Program
> Files\Python24\lib\site-packages\ZODB\Connection.py", line 252, in
> close
>     self.transaction_manager.unregisterSynch(self)
>   File "C:\Program
> Files\Python24\Lib\site-packages\transaction\_manager.py", line 169,
> in unre
> gisterSynch
>     ws.remove(synch)
>   File "C:\Program Files\Python24\Lib\site-packages\ZODB\utils.py",
> line 236, in remove
>     del self.data[id(obj)]
>   File "C:\Program Files\Python24\lib\UserDict.py", line 19, in __delitem__
>     def __delitem__(self, key): del self.data[key]
> KeyError: 26403280
>
> The reason why I'm doing this is because I'm trying to update the
> classes of persistent objects loaded into memory. I'm able to load the
> new classes just fine, but when I try to close the connection at
> program termination, I get the error:
>
> transaction.commit()
> conn.close()
> ConnectionStateError: Cannot close a connection joined to a transaction
>
> The only way I'm able to avoid this strange error is if I close all
> connections during the update, but since my update function runs in a
> different thread, it can't close the connections. Is there a way
> around this, or am I misunderstanding something?
>
> Chris
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