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

[Richard W.M. Jones]

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)

Without LIBGUESTFS_DEBUG/LIBGUESTFS_TRACE stdout + stderr should be
quite minimal for all tools.

Rich.

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