[openstack-dev] [oslo][mistral] Saga of process than ack and where can we go from here...

Doug Hellmann doug at doughellmann.com
Tue May 3 22:08:15 UTC 2016

Excerpts from Doug Hellmann's message of 2016-05-03 16:45:47 -0500:
> Excerpts from Joshua Harlow's message of 2016-05-03 14:24:13 -0700:
> > Howdy folks,
> > 
> > So I meet up with *some* of the mistral folks during friday last week at 
> > the summit and I was wondering if we as a group can find a path to help 
> > that project move forward in their desire to have some kind of process 
> > than ack (vs the existing ack then process) in there usage of the 
> > messaging layer.
> > 
> > I got to learn that the following exists in mistral (sad-face):
> > 
> > https://github.com/openstack/mistral/blob/master/mistral/engine/rpc.py#L38
> > 
> > And it got me thinking about how/if we can as a group possibly allow a 
> > variant of https://review.openstack.org/#/c/229186/ to get worked on and 
> > merged in and release so that the above 'hack' can be removed.
> Based on the comments on that patch, it looks like the consensus was to
> add a new method (to the client & dispatcher & whatever else needs it)
> to implement the new semantics. That way it's clear from the caller
> side what is expected, and it even makes it possible to adopt the new
> capability in other projects without having to go all-or-nothing.
> That said, I agree with Mehdi that *most* RPC calls throughout OpenStack,
> not being idempotent, should not use process-then-ack.

We also need to understand how the new semantics work for drivers other
than Rabbit. We have a lot of renewed interest in zmq for example.


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