moving Connection/PipeConnection between processes

jenifer adam jenigirly at gmail.com
Sat Jun 13 10:42:22 CEST 2009


On Jun 13, 1:11 pm, Mike Kazantsev <mk.frag... at gmail.com> wrote:
> On Sat, 13 Jun 2009 02:23:37 -0500
>
>
>
>
>
> Randall Smith <rand... at tnr.cc> wrote:
> > I've got a situation in which I'd like to hand one end of a pipe to
> > another process.  First, in case you ask why, a spawner process is
> > created early before many modules are imported.  That spawner process is
> > responsible for creating new processes and giving a proxy to the parent
> > process.
>
> ...
>
> > Looking at the pickle docs, I wonder if this could be resolved by adding
> > a __getnewargs__ method to _multiprocessing.Connection.  But even if
> > that would work I couldn't do it now since it's an extension module.
> > I've thought about trying to recreate the Connection.  Looks like it
> > should be possible with Connection.fileno().  The Unix portion looks
> > easy, but the win32 portion does not.
>
> > So if it's possible, what's the best way to pass a Connection to another
> > process?
>
> Pickle has nothing to do with the problem since it lay much deeper: in
> the OS.
>
> From kernel point of view, every process has it's own "descriptor
> table" and the integer id of the descriptor is all the process gets, so
> when you say "os.pipe()" kernel actually gives you a number which is
> completely meaningless for any other process - it either doesn't exists
> in it's descriptor table or points to something else.
>
> So, what you actually need is to tell the kernel to duplicate
> underlying object in another process' table (with it's own numbering),
> which is usually done via special flag for sendmsg(2) in C, so you
> should probably look out for py implementation of this call, which I
> haven't stumbled upon, but, admittely, never looked for.
>
> --
> Mike Kazantsev // fraggod.net
>
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