[Zope-dev] http://cvs.zope.org/Products/Scheduler vs Xron for cron-like functionality. Advice?

Romain Slootmaekers romain@zzict.com
Sat, 05 Oct 2002 13:26:31 +0200


Joachim Werner wrote:
>>Hi All,
>>I'm interested in starting to maintain Xron, if it has potential to be a
>>stable products.
>> From the code it doesn't seem to do any strange things, but I would
>>like to know if anybody has experience of using it in a production
>>environment, or any other experiences and that would recommend not
>>using it in a production environment.
> 
> 
> We are using it, but there seem to be some problems. One of them is that I
> frequently have cases where Xron doesn't reschedule properly (I am using the
> improved user interface stuff for Xron, so the bug could also be in there).
> What happens is that an event that is scheduled for daily execution at
> midnight will not be rescheduled for the next day after it was executed, but
> reset to the year 1970, which actually means it is switched off.

We are also using Xron in a production environment, and have the same 
problem, and also the reverse: Xron doesn't reschedule properly, does 
not reset the scheduled date, and when the server is restarted tries to 
"catch up" on all missed events. pretty annoying.
I think the problem is related to conflict errors that cause Zope to 
reissue the request.


> > Another issue is that Xron will use the current virtual host settings when
> it executes and reschedules an event. That means that the entries in the
> Xron Schedule ZCatalog will have different URLs. In some cases the URL that
> is used to execute an event could be important. E.g., we use Apache with
> some tricky rewrite rules in front of Zope, and to get around the Apache
> server the Zope server has to be called from a different URL.

This is a pain, Xron tries to invoke the actions from the front side of 
zope, ie by issuing a HTTP request. since we use a Zope+Apache 
http&https setup, we just hacked Xron to rewrite the urls to 
http://127.0.0.1:8080/......

Anyway, Xron is a backend zope product and
shouldn't try to do it's thing going through the main gates, especially 
if the
site is only reachable through https.
We really would like to something that just repeats itself after it's 
done, instead of just doing something every X hours.


> 
> I am willing to help with maintaining Xron, especially the part concerning
> ZEO, because we really need it ...
> 
> Joachim

same here because, at this point, we are considering moving to a cron 
based approach, and it would be nice if we would not need to do it.


Sloot.