Open Stack

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Hi all,

we have a Neutron backport proposed in stable/havana that is in grey
area in terms of applicability for stable branches. Located at [1].

The controversy is that it changes the default value of a
configuration setting, which is generally considered as a no-go for
backports. That said, it has additional aspects that may trigger the
exception.

Basically, the default value of the setting breaks all L3 agents we
have in our tree. The failure state is an unstoppable agent resync due
to incorrect gateway outside of subnet. To avoid the failure for any
L3 agent that we ship, users need to change the value of that setting
from default one.

It's also not clear what's the value of having a gateway outside the
current subnet. As of Juno, this 'feature' is obsolete and marked to
be removed in Kilo.

There is a change though that there are some third-party agents in the
wild that support that 'feature'; in that case, changing the default
value will affect them. Though we don't know whether they really
exist. All in all, the 'feature' won't be available for them since
Kilo, and there is no sign that its removal is controversial, so
probably no one is interested in it anyway.

So we have a dilemma: we may break the official stable rule of 'not
introducing inconmpatible configuration changes' and in that way fix
major failure scenario in Neutron; or we may leave everything as-is
(=our own agents broken) to stick to the rule.

My common sense tells me that we should fix our agents first, and then
think about potential third-party L3 agents that possibly rely on that
'feature' being enabled by default. Hence my +2 vote.

But your common sense may vary, so I'd like to hear from others on the
matter.

[1]: https://review.openstack.org/#/c/113129/

/Ihar
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