On Thu, Jun 26, 2014 at 4:12 AM, Daniel P. Berrange <[email protected]> wrote:
> 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. > How can we prevent libvirt issues like this from landing in trunk in the first place? If we don't figure out a way to prevent this from landing the first place I fear we will keep repeating this same pattern of failure. > > 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 > [email protected] > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >
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