[openstack-dev] [all] FYI - dropping non RabbitMQ support in devstack

Sean Dague sean at dague.net
Tue Jun 16 17:16:34 UTC 2015

On 06/16/2015 12:49 PM, Clint Byrum wrote:
> Excerpts from Sean Dague's message of 2015-06-16 06:22:23 -0700:
>> FYI,
>> One of the things that came out of the summit for Devstack plans going
>> forward is to trim it back to something more opinionated and remove a
>> bunch of low use optionality in the process.
>> One of those branches to be trimmed is all the support for things beyond
>> RabbitMQ in the rpc layer. RabbitMQ is what's used by 95%+ of our
>> community, that's what the development environment should focus on.
>> The patch to remove all of this is here -
>> https://review.openstack.org/#/c/192154/. Expect this to merge by the
>> end of the month. If people are interested in non RabbitMQ external
>> plugins, now is the time to start writing them. The oslo.messaging team
>> already moved their functional test installation for alternative
>> platforms off of devstack, so this should impact a very small number of
>> people.
> The recent spec we added to define a policy for oslo.messaging drivers is
> intended as a way to encourage that 5% who feels a different messaging
> layer is critical to participate upstream by adding devstack-gate jobs
> and committing developers to keep them stable. This change basically
> slams the door in their face and says "good luck, we don't actually care
> about accomodating you." This will drive them more into the shadows,
> and push their forks even further away from the core of the project. If
> that's your intention, then we need to have a longer conversation where
> you explain to me why you feel that's a good thing.

I believe it is not the responsibility of the devstack team to support
every possible backend one could imagine and carry that technical debt
in tree, confusing new users in the process that any of these things
might actually work. I believe that if you feel that your spec assumed
that was going to be the case, you made a large incorrect externalities

> Also, I take issue with the value assigned to dropping it. If that 95%
> is calculated as orgs_running_on_rabbit/orgs then it's telling a really
> lop-sided story. I'd rather see compute_nodes_on_rabbit/compute_nodes.
> I'd like to propose that we leave all of this in tree to match what is
> in oslo.messaging. I think devstack should follow oslo.messaging and
> deprecate the ones that oslo.messaging deprecates. Otherwise I feel like
> we're Vizzini cutting the rope just as The Dread Pirate 0mq is about to
> climb the last 10 meters to the top of the cliffs of insanity and battle
> RabbitMQ left handed. I know, "inconceivable" right?

We have an external plugin mechanism for devstack. That's a viable
option here. People will have to own and do that work, instead of
expecting the small devstack team to do that for them. I believe I left
enough of a hook in place that it's possible.

That would also let them control the code relevant to their plugin,
because there is no way that devstack was going to gate against other
backends here, so we'd end up breaking them pretty often, and it taking
a while to fix them in tree.


Sean Dague

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