Open Stack

Hello! I know there's been a lot of churn and misunderstanding over the
recent devstack changes, so I wanted to make it clear where we're going
with messaging drivers now that the policy [1] was approved.

According to the policy, drivers need to have at least 60% unit test
coverage, and an integration test suite with at least 3 "popular"
OpenStack projects, with preference for Nova, Cinder, and Glance, and
individuals who will support said test suite.

So, with that, the following is the status of each driver in tree right
now:

rabbit - 89% Unit test coverage. Being the default in devstack, and
the default in nearly every project's config files, this one is heavily
integration tested. There are multiple individuals who have proven to
be able to debug failures related to RabbitMQ and are well known in
the community.

qpid - Unit test coverage is at 77%, so it passes that bar. I cannot
find any integration testing being done, so it fails that. I also have
not found anyone who will step up and support it. So this should be
deprecated immediately.

zmq - Unit test coverage is 74%. There are no currently active integration
tests in OpenStack's infrastructure. Several individuals have self
identified as being willing to work on creating them. We have not had
the conversations yet about ongoing support. I recommend we continue to
support their effort to become policy compliant. If that does not solidify
by M3 of Liberty, or if the "new" zmq driver appears with integration
tests and support manpower, then we can deprecate at that time.

There's also the question of _how_ to deprecate them. I figure we should
deprecate when the driver is loaded. Is there an existing mechanism
that someone can point me to, or should I look at adding that to
oslo.messaging/stevedore?

[1] http://specs.openstack.org/openstack/openstack-specs/specs/supported-messaging-drivers.html