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Hi,

Thx a lot Előd for Your input on this topic.

On Thu, Dec 03, 2020 at 04:00:31PM +0100, Előd Illés wrote:
> Hi Slawek,
> 
> Thanks for turning to the mailing list with this issue and for the
> explanation!
> 
> In short: from stable core viewpoint I think this case could get an
> exception and we could merge back patch [3] to Victoria and Ussuri.
> 
> Here is my thinking:
> 
> - If I understand correctly, the critical code change ([1]) is already there
> in many release, in Ussuri (16.0.0, 16.1.0, 16.2.0) and Victoria (17.0.0).
> So I think it would not be fortunate to revert the code change, because it
> could cause some similar issue. (RPC change. Am I right?)
> - The code change is there from Ussuri, which means actually the RPC has
> changed already, only the versioning is missed.
> - Also, as you wrote, it would mean easier upgrades to backport patch [3].
> - Those, who already upgraded from Train to Ussuri probably bumped into the
> issue, so in case the change is reverted they will face an issue again.

Yes. All those points are correct.

> 
> Based on these and what you wrote I think now the less problematic way
> forward if we take an exception and propose + merge the backports.

That is our understanding too and that's why I asked for that here :)

> 
> If anyone has any other opinion or objection or sees any technical issue we
> haven't thought of, then let us know!
> 
> Thanks,
> 
> Előd
> 
> 
> On 2020. 12. 02. 18:51, Slawek Kaplonski wrote:
> > Hi,
> > 
> > Some time ago we backported in Neutron patch [1] which caused bug [2].
> > Patch [1] was merged in the Ussuri development cycle so it is already in
> > Ussuri and Victoria. Our mistake was that we merged it then without bump of
> > the RPC version and without code which would provide backward compatybility
> > between old agent and new neutron-server and that's why [2] happens.
> > 
> > Now, as we know that, we have proposed patch [3] to fix it in master branch.
> > And my question is - can we backport fix [3] to the stable/victoria and stable/
> > ussuri to fix the original issue caused by [1] there?
> > In general I know that we shouldn't do that but here are the reasons why we
> > would like to do it in this specific case:
> > - rpc version which we want to change now wasn't changed since Train at least
> > so there will be no any conflict with that,
> > - bump rpc version now and provide backward compatybility on neutron-server
> > will make upgrades Train->Ussuri and minor updates in Ussuri easier as there
> > will be no similar issue like is described in [2] anymore,
> > - patch [1] was already included in Ussuri and Victoria from master branch, it
> > wasn't really cherry-picked there so it actually should be there since the
> > beginning.
> > 
> > Based on those reasons mentioned about and also becuase in general it is
> > forbiden by stable policy to backport changes like that to stable branches I
> > would like to know opinion from wider community, especially stable-core-maint
> > team, about what would be the best approach to fix that issue: backport of [3]
> > to stable/{ussuri,victoria} or revert [1] in stable/{ussuri,victoria}.
> > 
> > [1] https://review.opendev.org/c/openstack/neutron/+/712632
> > [2] https://bugs.launchpad.net/neutron/+bug/1903531
> > [3] https://review.opendev.org/c/openstack/neutron/+/764108
> > 
> 

-- 
Slawek Kaplonski
Principal Software Engineer
Red Hat