RE: Dependencies on other hosts in a distributed application?

[Greg_Swift aotx uscourts gov]

> > > I find myself responsible for managing an ecosystem of rpms for our
> > > custom application. One of the interesting sticking points
> > is what we
> > > call the "db" rpm. Most of the other rpms won't run
> > correctly unless
> > > that rpm is installed. The catch is, it's got to be
> > installed on the
> > > database node(s) of the application, not the application nodes that
> > > the other rpms are being installed on.
> > >
> > > I haven't seen anything to indicate that the rpm format can handle
> > > such a dependency. Have I overlooked something? Anybody got *any*
> > > ideas on how such a thing might be handled?
> >
> > As far as I know it not a feature.  Most applications with
> > similar distributed configurations tend to rely on the db
> > client packages and then require you to setup the package
> > manually or with a script after the install.
> >
> > I guess there is one method you could try, although I'm sure
> > most packagers would disagree with the practice, as do I.
> > However this is an internal custom application, and I've been
> > placed in similar situations before.  You can try setting up
> > the check for the remote db inside the %pre script and
> > failing at that point if the check is unsuccessful.  This way
> > you can at least have a fairly controlled failure point based
> > on that dependancy before your rpm tries to do any additional
> > work.  Having typed it I like the idea even less, but there
> > it is.  Having re-read your question, I'm not sure if that is
> > what you are already doing or not.
>
>
> I alwayss hated the prescript, it breaks too much.
>
> So what we have done in situations like this:
>
> Make a faux client db package and require that.
> In the faux db package do the mojo, in particular we generate these faux
rpm
> from the "db server" so they have the proper config inside.

what type of proper configs does your application need to be present ?  is
it inside the scripts in the RPM itself that needs the configs to be there,
or does the application just not work after install if they arent?

-greg