Re: [libvirt] [Qemu-devel] [PULL 25/26] block: Remove deprecated -drive option serial
On Tue, Jul 10, 2018 at 17:01:22 +0200, Cornelia Huck wrote:
On Tue, 10 Jul 2018 16:39:31 +0200
Peter Krempa <pkrempa(a)redhat.com> wrote:
> On Tue, Jul 10, 2018 at 16:22:08 +0200, Cornelia Huck wrote:
> > On Tue, 10 Jul 2018 07:59:15 +0200
> > Markus Armbruster <armbru(a)redhat.com> wrote:
[...]
> > "ERROR: 'old_option' is deprecated and will be
removed; use 'modern_option' instead"
> >
> > and do an exit(1).
> >
> > Would that be workable?
>
> For delivering the warnings via monitor you'll need a store that will
> collect all the warnings and prepare them for delivery. You've got
> basically two options:
>
> 1) monitor command to poll for deprecated options
> 2) event with deprecated options
>
> Both require storing them since libvirt connects to the monitor only
> after the command line is processed.
>
> Warnings printed to stderr are nearly useless because until something
> breaks nobody bothers to read the log files.
So, from that I gather that a hard failure would be the easiest for
libvirt to detect (and everything else would become complicated really
quickly), right?
People start complaining only when stuff breaks. If anything is optional
people will usually not enable it. That makes any non-mandatory option
not work in most cases.
Since we are talking about deprecation we can't really make any of this
default though so there will always be a level of user interaction
required.
An option is to do a automatic testing where one of this approaches will
be enabled. For that you need a way to generate configurations which
libvirt would use in real life. We have a rather big collection of XMLs
which describe a valid configuration but the problem with using them on
a real qemu is that most of the disk paths/network targets/other
resources are made up and making them work with a real qemu would range
from being painful to being impossible.
If we start from scratch you then lack coverage.
If we fail with exit(1), can libvirt check any message that is
logged
right before that?
Yes we currently use this for very early failures which occur prior to
the monitor working.
> To make any reasonable use of -no-deprecated-options we'd
also need
> something that simulates qemu startup (no resources are touched in fact)
> so that we can run it against the testsuite. Otherwise the use will be
> limited to developers using it with the configuration they are
> currently testing.
Would that moan loudly that you should poke the libvirt developers if
some kind of testsuite failure is detected? Or am I misunderstanding?
Generally it should make somebody complain. But there is a problem.
Since we are talking deprecation it can't be enabled by default. And by
not making it default most of the users will not enable that option.
Who is, in general, testing which libvirt version? I can think of:
- libvirt developers, which will probably run libvirt current git, but
more likely a released QEMU?
Speaking for myself I run git+patches libvirt and git version of
qemu as I'm usually working with new features. (sometimes git+patches
qemu if it's a bleeding edge feature or fix for a feature)
- QEMU (and other related tools) developers, who will probably use
QEMU
current git, but a released libvirt
This is probably generally true.
- normal (technical) users and (integration) testers, who will
probably
use released versions of libvirt and QEMU
This too
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