[Zope-dev] Xron fragility

[Steve Alexander]

Chris McDonough wrote:
> 
> As a side note, I do not like the fact that Xron requires you to use special
> DTML methods.  I suppose this is a requirement in this architecture due to
> the fact they need to be autocataloged, but I don't really like that feature
> either :-).

I think Xron could work with anything that has "trigger" and "disarm"
methods, that gets put into the Schedule catalog.


> > > What does the Dispatcher thread do?  Does it fire off worker threads?
> >
> > Xron has a single dispatcher thread. This thread knows how long to sleep
> > for until the next job needs to run.
> 
> Do you think this is this any more effective than having a producer thread
> do a lookup every minute to see what jobs are current, after which it should
> put the current jobs in a queue?

What if you want a small job to be done every 30 seconds?

> > It uses Client.py to run a job.
> 
> Why is this?  This doesn't make any sense to me on its face.  Why not just
> call the method from a separate thread?

Which separate thread? Do you create a new ZODB thread? That sounds as
if it might use quite a few resources.

Is there a Zope API for making ZODB threads call methods on objects, as
signalled by other threads? I'm guessing the easiest way to do that is
to use Client.py to make a new http request.

> I see... would it be naive if I were to say that I think that a scheduler
> should fire off threads of its own and not rely on an external facility to
> run the jobs?

I'd really like to see a scheduler as a standard part of Zope.
I think it would be good to have scheduled methods called from within
Zope, rather then going through http. I don't know enough about how
ZPublisher/ZODB works to know where to start this though.

--
Steve Alexander
Software Engineer
Cat-Box limited
http://www.cat-box.net