On 4 Nov 2016, at 7:50, Jim Rollenhagen wrote:
> On Thu, Nov 3, 2016 at 3:04 PM, Joshua Harlow <[email protected]> wrote: >> Jay Faulkner wrote: >>>> >>>> On Nov 3, 2016, at 11:27 AM, Joshua Harlow<[email protected]> wrote: >>>> >>>> Just as a followup from the summit, >>>> >>>> One of the sessions (the new lib one) had a few proposals: >>>> >>>> https://etherpad.openstack.org/p/ocata-oslo-bring-ideas >>>> >>>> And I wanted to try to get clear owners for each part (there was some >>>> followup work for each); so just wanted to start this email to get the >>>> thoughts going on what to do for next steps. >>>> >>>> *A hash ring library* >>>> >>>> So this one it feels like we need at least a tiny oslo-spec for and for >>>> someone to write down the various implementations, what they share, what >>>> they do not share (talking to swift, nova, ironic and others? to figure >>>> this >>>> out). I think alexis was thinking he might want to work through some of >>>> that >>>> but I'll leave it for him to chime in on that (or others feel free to >>>> also). >>>> >>>> This one doesn't seem very controversial and the majority of the work is >>>> probably on doing some analysis of what exists and then picking a library >>>> name and coding that up, testing it, and then integrating (pretty >>>> standard). >>>> >>> >>> Ironic and Nova both share a hash ring implementation currently >>> (ironic-conductor and nova-compute driver for ironic). It would be sensible >>> to reuse this implementation, oslo-ify it, and have that code shared. >>> >>> I question the value of re-implementing something like this from scratch >>> though. >>> >>> Thanks, >>> Jay Faulkner >>> OSIC >>> >> >> Right I don't think the intention would be to implement it from scratch, but >> to do some basic analysis of what exists (and think about and document the >> patterns), and try to find the common parts (which likely involves renaming >> some specific nova/ironic methods from what I see); especially if we can get >> swift to perhaps (TBD) also use and contribute to this library. > > As the person who copied that code into Nova, the Nova code is a strict subset > of the Ironic code. > > Some of us talked to John Dickinson off-list, and it seems the Swift hash ring > has very different use cases and very different implementation. I > think we should > focus on pulling the Nova/Ironic code out first, and then talking to > Swift if we can > also make it work for them (sounds like it's not helpful today). > > // jim We had some great conversations last week face to face about this. The summary is that the "ring" in Ironic/Nova and the placement "ring" in Swift are vastly different in scope, requirements, and capabilities. I don't think it makes sense to try to unify them at this time. As always, I'm available to talk further about this, if you want. --John
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