[libvirt] [RFC 0/7] Warn at runtime when deprecated features are used

[Andrea Bolognani]

On Fri, 2018-10-05 at 11:56 +0200, Pavel Hrdina wrote:
> On Fri, Oct 05, 2018 at 11:38:14AM +0200, Andrea Bolognani wrote:
> > Warnings printed on stderr -> users and developers will actually
> > see them, be annoyed by them, eventually cave in and act upon them.
> > 
> > Warnings written to a log -> nobody will notice them, until one day
> > things suddenly stop working apparently out of the blue.
> > 
> > We might pretend that's not the case, but really, it is.
> 
> You cannot expect that libvirt will duplicate all the deprecation
> warnings from all hypervisors for all models or machine types or other
> values that can be set to a lot of different attributes in our XML.
> 
> Once we do that for machine type there will be requests to do it for
> other attributes as well.  I think that this is a big NO and way out
> of scope of libvirt.

Of course not, that would become very silly very fast - although
in many cases we already go out of our way to report a libvirt
error for configurations that would cause QEMU to ultimately bail
out anyway, so it wouldn't be entirely unprecedented either.

What I meant to say is that we should report deprecations of
*libvirt* features to the user directly instead of stuffing them
into a log file where they will possibly never be noticed until
it's way too late.

-- 
Andrea Bolognani / Red Hat / Virtualization