Excerpts from Ian Wells's message of 2016-08-31 12:30:45 -0700: > On 31 August 2016 at 10:12, Clint Byrum <cl...@fewbar.com> wrote: > > > Excerpts from Duncan Thomas's message of 2016-08-31 12:42:23 +0300: > > > On 31 August 2016 at 11:57, Bogdan Dobrelya <bdobre...@mirantis.com> > > wrote: > > > > > > > I agree that RPC design pattern, as it is implemented now, is a major > > > > blocker for OpenStack in general. It requires a major redesign, > > > > including handling of corner cases, on both sides, *especially* RPC > > call > > > > clients. Or may be it just have to be abandoned to be replaced by a > > more > > > > cloud friendly pattern. > > > > > > > > > Is there a writeup anywhere on what these issues are? I've heard this > > > sentiment expressed multiple times now, but without a writeup of the > > issues > > > and the design goals of the replacement, we're unlikely to make progress > > on > > > a replacement - even if somebody takes the heroic approach and writes a > > > full replacement themselves, the odds of getting community by-in are very > > > low. > > > > Right, this is exactly the sort of thing I'd like to gather a group of > > design-minded folks around in an Architecture WG. Oslo is busy with the > > implementations we have now, but I'm sure many oslo contributors would > > like to come up for air and talk about the design issues, and come up > > with a current design, and some revisions to it, or a whole new one, > > that can be used to put these summit hallway rumors to rest. > > > > I'd say the issue is comparatively easy to describe. In a call sequence: > > 1. A sends a message to B > 2. B receives messages > 3. B acts upon message > 4. B responds to message > 5. A receives response > 6. A acts upon response > > ... you can have a fault at any point in that message flow (consider > crashes or program restarts). If you ask for something to happen, you wait > for a reply, and you don't get one, what does it mean? The operation may > have happened, with or without success, or it may not have gotten to the > far end. If you send the message, does that mean you'd like it to cause an > action tomorrow? A year from now? Or perhaps you'd like it to just not > happen? Do you understand what Oslo promises you here, and do you think > every person who ever wrote an RPC call in the whole OpenStack solution > also understood it? > > I have opinions about other patterns we could use, but I don't want to push > my solutions here, I want to see if this is really as much of a problem as > it looks and if people concur with my summary above. However, the right > approach is most definitely to create a new and more fitting set of oslo > interfaces for communication patterns, and then to encourage people to move > to the new ones from the old. (Whether RabbitMQ is involved is neither > here nor there, as this is really a question of Oslo APIs, not their > implementation.)
I think it's about time we get some Architecture WG meetings started, and put "Document RPC design" on the agenda. __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
