[Zope] Zope and threads.

[Chris McDonough]

On Tue, 2005-02-22 at 15:22, Pascal Peregrina wrote:
> Ok, so, this almost completely answers my question.
> 
> Let me tell you more about what I am doing, because I agree that my initial
> mail was not that clear. :)
> 
> I am trying to implement a ZeroConf browser (http://www.zeroconf.org/) in
> Zope to automatically get the network location of XML RPC services that my
> Zope objects talk to.
> 
> The ZMI part is easy. In my new product, I've got my object in the Control
> Panel, and it is ready to display whatever data I want (for example the list
> of discovered services).
> 
> The ZeroConf implementation itself has already been made by someone else
> (http://sourceforge.net/projects/pyzeroconf)
> 
> So I am just trying to plug pieces together now :)
> 
> >From my product, I need to start a thread that will run the ZeroConf code,
> and ZeroConf data will then be accessible through a particular object of
> this code (the "listener" to be exact, as they call it in pyzeronf).
> 
> This thread should be started when Zope starts, so I guess I can put it in
> the __init__.py of my product.
> 
> I only got one issue : my product can be refreshed.
> So how can I ensure that the ZeroConf stuff won't be re-initialized if I
> refresh my product ? (ending with 2 threads, with one of the threads not
> being used). I know this is more a python related question, but I haven't
> found a precise answer on the net.

I'm not sure of how the internals of refresh work (I dont use it) but I
suspect that if you do something like:

import sys
if not getattr(sys, 'ZEROCONF_STARTED'):
   .. start the thread ..
   sys.ZEROCONF_STARTED = 1

It will not spawn another thread.  "sys" is just an example here, any
module namespace should work (even __builtins__ probably).