Open Stack

I believe that the RPC backend should no longer have any default.



Historically, it seems that the Kombu driver is default only because it existed before all others and before there was an abstraction. With multiple implementations now available, it may be time for a change.

Why?
* A default skews the attitudes and subsequent architectures toward a specific implementation


* A default skews the practical testing scenarios, ensuring maturity of one driver over others.
* The kombu driver does not work "out of the box", so it is no more reasonable as a default than impl_fake.
* The RPC code is now in openstack-common, so addressing this later will only create additional technical debt.

My proposal is that for Folsom, we introduce a "future_required" flag on the configuration option, "rpc_backend". This will trigger a WARNING message if the rpc_backend configuration value is not set.  In Grizzly, we would make the rpc_backend variable mandatory in the configuration.

Mark McLoughlin wisely suggested this come before the mailing list, as it will affect a great many people. I welcome feedback and discussion.

Regards,
Eric Windisch