Re: [Modeling-users] Warning: possible problem with Zope, maybe MT-related

[Sebastien B. <sbi...@us...>]

Jerome Kerdreux <Jer...@fi...> writes:
> On Fri, Mar 07, 2003 at 10:53:08AM +0100, Sebastien Bigaret wrote:
> >=20
> > It seems that the problem is triggered when the same psycopg cursor=
 is
> > used in two different threads.
>=20
>=20
> This is really sound strange as, i know zope use medusa asyncore, and=
=20
> this avoid the use of thread (for the http..) so how could you achieve
> to have several thread using the same db connection. ?=20
>=20

  You made me doubt about this, but I checked and Zope does use threads
  indeed. I included at the end the short list of modules I visited to
  make sure: Zope uses the asyncore to dispatch its request (and, right,
  the dispatch itself is done without forking & w/ no thread, but with
  select()), and these requests are then handled by a dedicated number
  of threads. There's also a nice explanation of this mechanism at
  http://lists.initd.org/pipermail/psycopg/2003-March/001906.html but
  beware! There is a guru wearing a warm cloak of invisibility (+2)
  roaming around! ;)

> Is there someone else using modeling over zope ? cause i read severals
> post over last weeks about the lack on this kind of things in zope=20
> (mainly #plone ) and the zope community seems to try different ways
> as CMFTypes and Adaptable Storage.=20

  I'm using it, but that you already know. And yes, the way the
  framework can be used along w/ zope is still to be documented.

> /Soaf which is going to test modeling over mysql :)=20

  Great! I'll wait for your reports then.

        Cheers,

-- S=E9bastien.



------------------------------------------------------------------------
Zope uses threads (possible errors of interpretation of code are all
                   mine):

z2.py
        from ZServer import setNumberOfThreads
        setNumberOfThreads(NUMBER_OF_THREADS)
        [...]
        if HTTP_PORT:
          [...]
          hs =3D zhttp_server( [...]

ZServer/HTTPServer.py:=20
    zhttp_server derives from http_server, and uses zhttp_channel for
    its channel_class

    zhttp_channel itself derives from http_channel, and uses
    ZServer.PubCore.handle in its work() method

Last, ZServer.PubCore.__init__ declares handle as
ZRendezvous.ZRendevous(_n).handle, where ZRendeVous is declared in
ZServer.PubCore.ZRendezvous and creates a pool of threads:

(and where _n is assigned by setNumberOfThreads() above in z2.py for
option '-t n': "The number of threads to use, if ZODB3 is used.")

        class ZRendevous:
            def __init__(self, n=3D1):
                [...]
                while n > 0:
                    l=3Dthread.allocate_lock()
                    l.acquire()
                    pool.append(l)
                    thread.start_new_thread(ZServerPublisher,=20
                                            (self.accept,))

------------------------------------------------------------------------