Re: [naviserver-devel] ns_atstartup and order of execution?

[Stephen D. <sd...@gm...>]

On 10/20/05, Zoran Vasiljevic <zv...@ar...> wrote:
>
> Am 19.10.2005 um 18:16 schrieb Zoran Vasiljevic:
>
> > Hi !
> >
> > We have a pretty elaborate (and sometimes confusing) mechanism
> > for running various atXXX scripts.
> >
> > So, if I would like to:
> >
> >   ns_atstartup X
> >   ns_atstartup Y
> >   ns_atstartup Z
> >
> > then the server will execute:
> >
> >   Z
> >   Y
> >   X
> >
> > i.e. in the *reverse* order. This is because all of those
> > are just entered in a single-linked list and the head of
> > the list points always to the *last* registered item.
> >
> > This is suboptimal.
> >
> > In many real world scenarios, I will like to use the ns_atstartup
> > to schedule couple of scripts to do various initialization things.
> > It is often so that Y will depend on X and Z on Y to be successfull.
> > At the moment, I'm (mis)using the ns_job with a single thread and
> > post the jobs there, because it will then exectue them in FIFO fashion
> > (which is what I need). BUT: this is of course not optimal as it runs
> > parallely with the server startup and I have to be carefull to
> > accomodate
> > for that.
> >
> > So, I'm all for reversing the logic of script execution i.e. doing the
> > more natural way of runing them in FIFO fashion (now we have LIFO).
> > But, I'm afraid of the potential compatibility problems. What I would
> > like to see is if any of you would have objections to reversing the
> > logic, and if yes, ideas how we could make this compatible?
> > One idea would be:
> >
> >    ns_atXXX ?-tail? $theScript
> >
> > I'd rather go after FIFO list walk then adding yet-another-option,
> > but I'm open to suggestions...
>
> I've done the coding.
>
> All ns_atXXX EXCEPT ns_atshutdown will now execute callbacks in FIFO
> fashion. The ns_atshutdown will execute the callbacks in LIFO fashion.
> This seems more natural to me. If nobody has anyhing against
> (Vlad already expressed himself) I will commit this.


FIFO makes sense to me.  Thanks for the change.

Not sure about LIFO for shutdown callbacks though.  Does it make
sense?  It's one extra thing to remember...