[Libguestfs] virt-sparsify failed (was: [oVirt Jenkins] ovirt-system-tests_basic-suite-master_nightly - Build # 479 - Failure!)

[Nir Soffer]

On Tue, Oct 13, 2020 at 7:15 PM Richard W.M. Jones <rjones at redhat.com> wrote:
>
> On Tue, Oct 13, 2020 at 06:45:42PM +0300, Nir Soffer wrote:
> > I think this is the right solution - when virt-something tool fails,
> > it should log the reason for the failure - the error that caused the
> > tool to fail. I'm not sure this is easy to do as the failing code
> > run inside a special VM. Maybe the code running in the VM should log
> > the output in a machine readable way, so once an error is detected
> > virt-something can report the error as the reason, without running
> > in debug mode.
>
> All the virt-* tools that I've written have a non-zero exit code and
> print an error message on stderr when they fail.  Errors from inside
> the appliance are propagated to the library and thence to the tool
> correctly.
>
> I think the best thing to do is:
>
>  - spool up stdout + stderr from the tool
>
>  - if the exit code != 0, save the spooled output for analysis
>
>  - if the exit code == 0, discard it (or keep it if you like)

This is what we already do, and the result is not helpful. If you look
at the log message in the previous message, basically the only
info about the error is:

    libguestfs error: guestfs_launch failed

I don't see what we can do with this error message.

If this is an error running qemu, the error message from qemu can help
to understand why qemu failed to start.

> Without LIBGUESTFS_DEBUG/LIBGUESTFS_TRACE stdout + stderr should be
> quite minimal for all tools.
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
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>