[openstack-dev] Quantum + ZeroMQ (with a sprinkling of Nova) in Folsom

Dan Wendlandt dan at nicira.com
Tue Sep 25 21:12:00 UTC 2012

On Tue, Sep 25, 2012 at 1:45 PM, Mark McLoughlin <markmc at redhat.com> wrote:
> On Tue, 2012-09-25 at 13:28 -0400, Eric Windisch wrote:
>> Russell, perhaps. The issue is that if the message format changes, it
>> would be lower cost to do it now. Also, I'm moving this to the public
>> list, because I agree that it is a good time to do it.
>> IF there is an RC3 for Nova, I'd like for consideration to get the
>> message-format change in, because it reduces complexity for Grizzly
>> (having to understand two formats), and because it will make the
>> Quantum code supportable. This binary needs to move outside of Nova to
>> avoid this unnecessary interdependency.
>> It might be resolvable by adding a version to the message format, but
>> it doesn't solve the problem today - which, arguably, doesn't have to
>> be solved. We can just release with the zeromq stuff broken in Quantum
>> for Folsom, without any ability to backport, and I'm prepared for that
>> to happen. I've just rallied for a best-effort to get it in, because
>> it would be a nice to have, after finding out at F3 that it wouldn't
>> work.
>> As it is, the patch that is already in Quantum should be enough to get
>> us going for Folsom if we can also get the patch into Nova. The two
>> patches pending review can be backported, if necessary.
> It took me a while to make any sense of this
> This change which was merged into openstack-common a few days ago:
>   https://review.openstack.org/11408
> is what changed the message format?
> I must admit I didn't realize there was a backwards compatibility issue
> with that patch.
> So, the message format used by zmq in Nova is incompatible with what's
> used in Quantum.
> At this point I'd be inclined to document the zmq driver as unstable and
> warn users that it's only included in Folsom as a "preview". Making
> incompatible changes days before the release should tell us that we're
> not ready to commit to maintaining compatibility with this driver yet.
> If we don't document it as unstable, we have two choices before the
> final Folsom release - either merge the new format into Nova or revert
> it from Quantum.

Please note: the zmq change in quantum was merged into master (i.e.,
grizzly) but was not merged into milestone-proposed (i.e., folsom),
since problems were discovered after the initial merge, but prior to
deciding whether to include it in Folsom.   Thus, I don't think we
need to worry about reverting anything in Quantum, at least not for


> Cheers,
> Mark.

Dan Wendlandt
Nicira, Inc: www.nicira.com
twitter: danwendlandt

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