[openstack-dev] blueprint amqp-rpc-fast-reply-queue

Ray Pekowski pekowski at gmail.com
Wed Jan 30 00:15:51 UTC 2013

On Tue, Jan 29, 2013 at 5:32 PM, Eric Windisch <eric at cloudscaling.com>wrote:

> > "Grizzly would also, by default, be able to send and reply to Folsom, as
> well as receive replies from Folsom as long as compatibility mode is not
> disabled."
> Yes, it can do both, but not at the same time. Without listening on two
> queues, the code does one-or-the-other, but not both. The code is either
> forwards OR backwards compatible. It would be much easier for migrations if
> it can be both.

With my change and compatibility mode enabled, all requests are sent in the
old message format and replies listened for on the old queue.  If the call
is sent to Folsom, it will come back on the old queue.  If the call is sent
to Grizzly(fast) or Havana, those versions will recognize the old message
format and reply on the old queue.  So Grizzly won't have to do listen on
both to be able to communicate in all the ways you say the dual queue
listen approach can.

If Folsom calls Grizzly(compat), Grizzly(compat) will recognize the old
format and respond on the old queue.  If Grizzly(fast) or Havana calls
Grizzly(compat), Grizzly(compate) will recognize the new format and respond
on the new queue.

What else is needed?  How is that any less functional than the dual queue
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