On Thu, Jun 26, 2014 at 07:00:32AM -0400, Sean Dague wrote: > While the Trusty transition was mostly uneventful, it has exposed a > particular issue in libvirt, which is generating ~ 25% failure rate now > on most tempest jobs. > > As can be seen here - > https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L294-L297 > > > ... the libvirt live_snapshot code is something that our test pipeline > has never tested before, because it wasn't a new enough libvirt for us > to take that path. > > Right now it's exploding, a lot - > https://bugs.launchpad.net/nova/+bug/1334398 > > Snapshotting gets used in Tempest to create images for testing, so image > setup tests are doing a decent number of snapshots. If I had to take a > completely *wild guess*, it's that libvirt can't do 2 live_snapshots at > the same time. It's probably something that most people haven't hit. The > wild guess is based on other libvirt issues we've hit that other people > haven't, and they are basically always a parallel ops triggered problem. > > My 'stop the bleeding' suggested fix is this - > https://review.openstack.org/#/c/102643/ which just effectively disables > this code path for now. Then we can get some libvirt experts engaged to > help figure out the right long term fix.
Yes, this is a sensible pragmatic workaround for the short term until we diagnose the root cause & fix it. > I think there are a couple: > > 1) see if newer libvirt fixes this (1.2.5 just came out), and if so > mandate at some known working version. This would actually take a bunch > of work to be able to test a non packaged libvirt in our pipeline. We'd > need volunteers for that. > > 2) lock snapshot operations in nova-compute, so that we can only do 1 at > a time. Hopefully it's just 2 snapshot operations that is the issue, not > any other libvirt op during a snapshot, so serializing snapshot ops in > n-compute could put the kid gloves on libvirt and make it not break > here. This also needs some volunteers as we're going to be playing a > game of progressive serialization until we get to a point where it looks > like the failures go away. > > 3) Roll back to precise. I put this idea here for completeness, but I > think it's a terrible choice. This is one isolated, previously untested > (by us), code path. We can't stay on libvirt 0.9.6 forever, so actually > need to fix this for real (be it in nova's use of libvirt, or libvirt > itself). Yep, since we *never* tested this code path in the gate before, rolling back to precise would not even really be a fix for the problem. It would merely mean we're not testing the code path again, which is really akin to sticking our head in the sand. > But for right now, we should stop the bleeding, so that nova/libvirt > isn't blocking everyone else from merging code. Agreed, we should merge the hack and treat the bug as release blocker to be resolve prior to Juno GA. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| _______________________________________________ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev