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

On Tue, Oct 13, 2020 at 8:40 PM Richard W.M. Jones <rjones(a)redhat.com&gt; wrote: > > On Tue, Oct 13, 2020 at 07:56:29PM +0300, Nir Soffer wrote: > > On Tue, Oct 13, 2020 at 7:15 PM Richard W.M. Jones <rjones(a)redhat.com&gt; 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. > > Right, so in this particular instance the error message would tell us > that you should run libguestfs-test-tool because your qemu/kernel/etc > is broken in some way :-/ > > There's not a particularly good answer here if you don't want to ever > use LIBGUESTFS_DEBUG/LIBGUESTFS_TRACE, but perhaps you could run > libguestfs-test-tool if you see any error which matches the substring > /guestfs_launch/ ? Another (orthogonal?) option: Make LIBGUESTFS_DEBUG/LIBGUESTFS_TRACE log elsewhere, not to stdout/err (e.g. some other file descriptor, or to a file passed via env or whatever). This way, it might make sense for vdsm to always pass these vars, continue logging all stdout/err, and log/keep debug/trace logs only on errors.