[Libosinfo] Resources inheritance for OSes, I need some help/feedback!

[Daniel P. Berrangé]

On Tue, Nov 13, 2018 at 11:27:47AM +0100, Fabiano Fidêncio wrote:
> On Tue, 2018-11-13 at 09:58 +0000, Daniel P. Berrangé wrote:
> > On Tue, Nov 13, 2018 at 10:10:17AM +0100, Fabiano Fidêncio wrote:
> > > People,
> > > 
> > > I'm working on making OsinfoResources inherited for OSes that
> > > derives-
> > > from/clones another OSes. The inheritance, IMO, should work like:
> > > - os1 has:
> > >   <resources arch="all">
> > >     <minimum>
> > >       <cpu>1000000000</cpu>
> > >       <ram>1073741824</ram>
> > >     </minimum>
> > >   </resources>
> > > 
> > > - os2, which inherits the values from os1, has:
> > >   <resources arch="all">
> > >     <minimum>
> > >       <n-cpus>2</n-cpus>
> > >     </minimum>
> > >   </resources>
> > 
> > I wonder about making inheritance explicit, eg for os2, have
> > 
> >    <resources arch="all" inherit="yes">
> >      <minimum>
> >        <n-cpus>2</n-cpus>
> >      </minimum>
> >    </resources>
> > 
> > the benefit of this is that....  [1]
> 
> Okay, this idea makes things easier, I like it.
> 
> > 
> > > - When calling osinfo_resources_get_cpu(os2), I'd expect to get:
> > > 1000000000.
> > > 
> > > 
> > > In order to achieve so, we'll need a few more changes in the way
> > > resources are added to OSes:
> > > - Do *not* have duplicated resources for the same OS;
> > >   - This can be easily done in osinfo_os_add_*_resources() + tests
> > > to
> > > catch this situation;
> > > - Do *not* have more than one resources with the same arch for the
> > > same
> > > OS;
> > >   - Although this can be easily done  in
> > > osinfo_os_add_*_resources() as
> > > well, I'd go only for tests to catch this situation;
> > 
> > These points look tangential to inheritance to me. Or to put it
> > another
> > way, shouldn't we ensure uniqueness regardless of whether we have
> > inheritance or not.
> 
> What would be the use case of having different resources set for the
> very same architecture in an OS?

I don't see any need for it - I'm saying that we should ensure
uniqueness regardless. It is just a separate (bug fix) work item
from inheritance

> > 
> > 
> > > - Have a way to specify that a resource field shouldn't be
> > > inherited;
> > >   - Here I can basically see two different approaches, and my
> > > personal
> > > preference would be the former:
> > >     - A specific value to be set to the field that will just be
> > > checked
> > > when merging the resources' content when doing the inheritance
> > > (suggestions are welcome and remember we can't use -1);
> > >     - Add an extra attribute to the elements and have a new
> > > structure
> > > (similar to DeviceLinks) and play with it in the same way I
> > > proposed
> > > for removed devices*.
> > 
> > [1]...you solve this problem more attractively IMHO.
> > 
> > Regards,
> > Daniel
> 
> Best Regards,
> -- 
> Fabiano Fidêncio
> 

Regards,
Daniel
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