Hi, 2011/12/21 Andrew Brown <brow...@gmail.com>
> Hello everyone, > > I've been playing around with distributed computing with multiprocessing > on CPython, and thought I'd see if I could spin up some workers running > pypy and have them connect to a server running CPython. > > Well, it didn't go so well. The client always gets an IOError: bad message > length in the answer_challenge() function of connection.py. > > Traceback (most recent call last): >> File "app_main.py", line 51, in run_toplevel >> File "client1.py", line 6, in <module> >> m.connect() >> File >> "[...]/pypy-1.7/lib-python/modified-2.7/multiprocessing/managers.py", line >> 474, in connect >> conn = Client(self._address, authkey=self._authkey) >> File >> "[...]/pypy-1.7/lib-python/modified-2.7/multiprocessing/connection.py", >> line 149, in Client >> answer_challenge(c, authkey) >> File >> "[...]/pypy-1.7/lib-python/modified-2.7/multiprocessing/connection.py", >> line 383, in answer_challenge >> message = connection.recv_bytes(256) # reject large message >> IOError: bad message length > > > You can try the simple example from the documentation: > http://docs.python.org/library/multiprocessing.html#using-a-remote-manager to > trigger this. Obviously CPython server and CPython client works, but I've > also found that pypy server and pypy client works as well. It's only a > mixed server and client that triggers this same error. (either way... pypy > server + cpython client or cpython server + pypy client) > > Is this a bug? Or is multiprocessing not supposed to be compatible across > implementations? I would think it is, since it's just sockets with pickled > data, right? > It's something I overlooked at the time: in pypy/module/_multiprocessing/interp_connection.py, the function do_send_string() has this short comment "# XXX htonl!". My bad. Of course it does not make any difference when client and servers run pypy on comparable architectures, but CPython correctly calls htonl, and ntohl when receiving. -- Amaury Forgeot d'Arc
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