[openstack-dev] [neutron][stable] - exception for stable/kilo DVR back-ports

Kevin Benton kevin at benton.pub
Wed May 4 22:38:27 UTC 2016


So I was doing some testing and this looks like it will happen very quickly
after an agent restarts.

The rule priorities are stored as a set and are allocated from by calling
.pop(). In local testing, it looks like that pretty consistently pulls the
first priority off of the range. http://paste.openstack.org/show/496168/

This means that after restarting an l3 agent, a newly associated floating
IP will likely have the same priority as another one already on the agent.
Then when either floating IP is disassociated, it will break the other one.

On Wed, May 4, 2016 at 3:20 PM, Armando M. <armamig at gmail.com> wrote:

>
>
> On 4 May 2016 at 14:26, Assaf Muller <assaf at redhat.com> wrote:
>
>> On Wed, May 4, 2016 at 4:54 PM, Kevin Benton <kevin at benton.pub> wrote:
>> > Hello,
>> >
>> > I would like to propose a freeze exception for
>> > https://review.openstack.org/#/c/312253/ and
>> > https://review.openstack.org/#/c/312254/ . They address a bug in DVR
>> that
>> > causes floating IPs to eventually break after an L3 agent has been
>> > restarted. It's a serious bug but it's very subtle because it takes a
>> busy
>> > system and bad luck to trigger it.
>> >
>> > If we decide against the back-port a workaround could be to advise all
>> > distros/operators to call the namespace cleanup script every time the l3
>> > agent is restarted, which would prevent this issue, but at the cost of
>> > disrupting traffic on the agent restart.
>>
>> That's not something I could seriously suggest to users, meaning that
>> said users will just cherry pick these patches anyway. Might as well
>> prevent the pain proactively and merge it to stable/kilo.
>>
>
> Bear in mind that we don't test DVR on kilo [1] and taking into
> consideration also the likelihood of the issue, I would advise against the
> backport.
>
> [1]
> https://github.com/openstack-infra/project-config/blob/master/zuul/layout.yaml#L2261
>
>
>>
>> >
>> >
>> > Cheers,
>> > Kevin Benton
>> >
>> >
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