Hi,
Briefly, when using the multiprocessing module, when exceptions are
thrown, they need to be pickleable in order to propagate, since that is
how multiprocessing passes information around.
See
http://stackoverflow.com/questions/8785899/hang-in-python-script-using-sqlalchemy-and-multiprocessing
and Python bug http://bugs.python.org/issue1692335 for background.
I've reported bugs http://bugs.python.org/issue13751 and
http://www.sqlalchemy.org/trac/ticket/2371 and
http://psycopg.lighthouseapp.com/projects/62710-psycopg/tickets/90-psycopg-exceptions-cannot-be-pickled
and http://bugs.python.org/issue13760 in this context. I've been reporting
them as I came across them.
I can produce a complete example if necessary, but I think the problem is
pretty obvious. Let me know whether you require followup action from me.
Specifically, do you want me to report a bug?
See below the traceback I just ran into. Please CC me on all replies.
Thanks.
Regards, Faheem
*******************************************************************
Process PoolWorker-1:
Traceback (most recent call last):
File "/usr/lib/python2.6/multiprocessing/process.py", line 232, in
_bootstrap
Process PoolWorker-2:
Traceback (most recent call last):
File "/usr/lib/python2.6/multiprocessing/process.py", line 232, in _bootstrap
self.run()
File "/usr/lib/python2.6/multiprocessing/process.py", line 88, in run
self._target(*self._args, **self._kwargs)
File "/usr/lib/python2.6/multiprocessing/pool.py", line 71, in worker
self.run()
File "/usr/lib/python2.6/multiprocessing/process.py", line 88, in run
self._target(*self._args, **self._kwargs)
File "/usr/lib/python2.6/multiprocessing/pool.py", line 71, in worker
put((job, i, result))
File "/usr/lib/python2.6/multiprocessing/queues.py", line 366, in put
put((job, i, result))
File "/usr/lib/python2.6/multiprocessing/queues.py", line 366, in put
return send(obj)
PicklingError: Can't pickle <class 'Boost.Python.ArgumentError'>: import
of module Boost.Python failed
return send(obj)
PicklingError: Can't pickle <class 'Boost.Python.ArgumentError'>: import
of module Boost.Python failed
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