[openstack-dev] [nova] [os-vif] [neutron] Race in setting up linux bridge

Sean Dague sean at dague.net
Mon Aug 29 11:52:41 UTC 2016

On 08/26/2016 05:23 PM, Armando M. wrote:
> Folks,
> Today I spotted [1]. It turns out Neutron and Nova might be racing
> trying to set up the bridge to provide VM with connectivity/dhcp. In the
> observed failure mode, os-vif fails in [2].
> I suppose we might need to protect the bridge creation and make it
> handle the potential exception. We would need a similar fix for Neutron
> in [3].
> That said, knowing there is a looming deadline [4], I'd invite folks to
> keep an eye on the bug.
> Many thanks,
> Armando
> [1] https://bugs.launchpad.net/neutron/+bug/1617447
> [2] https://github.com/openstack/os-vif/blob/master/vif_plug_linux_bridge/linux_net.py#L125
> [3] http://git.openstack.org/cgit/openstack/neutron/tree/neutron/agent/linux/bridge_lib.py#n58
> [4] http://lists.openstack.org/pipermail/openstack-dev/2016-August/102339.html

Is this another issue where 2 processes are calling "locked" code, but
from different projects, so the locks have no impact? We just went
through this with os-brick and had to mitigate with a retry block.

We probably need to make some strong rules about what locking can look
like in these common libraries, because they have a lot of ported code
that doesn't really work when communicating between 2 services.


Sean Dague

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