[ZODB-Dev] BTreeFolder2 causes "RuntimeError: Shouldn't load state for"?

[Syver Enstad]

Dieter Maurer <dieter at handshake.de> writes:

> Persistent objects must never:
> 
> 
>   *  not be passed between threads

Is it okay to just read persistent objects after a thread has modified
them? Since I am using ZODB with Twisted web I am thinking of the
following scenario. Since twisted has a mainloop it would be prudent
to shuffle off a long running operation involving ZODB to a thread so
that other web requests can be handled. After the thread has finished
processing I want to display the object(s) that changed.

Sketch:

In the web page (mainloop):

Open a new connection: (I am always using setLocalTransaction to not
make the transaction thread bound).  Spawn off a thread and pass the
connection to it. Set up a callback for further processing when the
thread is done.

In worker thread:
Do processing 
connection.getTransaction().commit()
return interesting Persistent objects.

In the web page (mainloop):
Receive result in callback and display it (generate html).

If this is not possible I'd like to hear why.