[ZODB-Dev] Threads and Connections

[Chris S]

On 7/26/06, Chris McDonough <chrism at plope.com> wrote:
> FWIW I believe by default at least, open ZODB connections are tied to
> the thread which did the opening (they are returned to a pool when
> closed and reused, possibly in another thread).  And indeed each
> connection does have a cache; caching is one of the primary
> responsibilities of a connection object.
>
> See the documentation in ZODB/interfaces.py for "IConnection".
>
> I *think* what is happening here is that you are committing the
> transaction devoted to the current connection/thread, and trying to
> close a connection that has pending changes from another thread.  So
> when you do transaction.abort(), it's aborting the transaction
> involving the current thread, not the one associated with the other
> connection.
>
> That said, I'm not entirely sure what to tell you to do here; there
> used to be an API named "setLocalTransaction" or somesuch that
> allowed you to control the one-thread-per-connection policy wrt to a
> transaction minimally, IIRC.  This API has disappeared, probably
> replaced with something more flexible, but I'm not sure what that
> is.  I suspect it may have something to do with the
> transaction_manager parameter to DB.open() however.

Thanks, using a single transaction manager along with setting
conn._needs_to_join = True right before I close the connection appears
to fix the problem. It's a bit of a hack, but it works.

Chris