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On 07/13/2015 05:08 PM, Kevin Benton wrote:
> Thanks for the info. So the equivalent in neutron would be if we just
> ensure backward compatible AMQP APIs, right?

There's a few parts:

1) Backwards compatibility with changes to the oslo.messaging APIs using
API versioning (what you're referring to, I think).  Neutron does this
(though not tested in a mixed version mid-upgrade environment yet).

2) Compatibility of the data sent over those interfaces.  This is where
oslo.versionedobjects comes in.  Breakage here is much easier to miss
since it's not always obvious when you're modifying a data structure
that's sent over the wire.  There has been a ton of work in Nova to
version the data sent over the wire and have the ability for a service
(nova-conductor in nova's case) to be able to convert objects back to a
version that an older service can understand.  This is the most likely
way Neutron will break rolling upgrades right now, especially since it's
not tested.

3) DB schema.  Depending on what services access the db directly and
what the rolling upgrade strategy is, there may be some additional
constraints on making sure the db schema is backwards copmatible, too.

-- 
Russell Bryant

> On Mon, Jul 13, 2015 at 7:33 AM, Russell Bryant <rbryant at redhat.com
> <mailto:rbryant at redhat.com>> wrote:
> 
>     On 07/13/2015 04:09 AM, Kevin Benton wrote:
>     >>because you won't have to run Neutron agents on compute nodes anymore.
>     >
>     > How will upgrades work for OVN?
> 
>     We haven't written anything down yet, but here's what I expect.
> 
>     Right now we're still changing the db schema however is needed without
>     messing with versioning.  As we get to "production ready", I expect
>     we'll start being strict about only making backwards compatible ovsdb
>     schema changes to make upgrades easier.
> 
>     There are 2 central components - ovn-northd and ovsdb-server - that
>     would be upgraded first, which I would expect to be done at the same
>     time as upgrading your Neutron control plane.  As long as any ovsdb
>     schema changes are backwards compatible, you could do rolling-upgrades
>     of ovn-controller on compute or network nodes.
> 
>     --
>     Russell Bryant
> 
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> 
> -- 
> Kevin Benton
> 
> 
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-- 
Russell Bryant