[openstack-dev] [Nova] bp proposal: discovery of peer instances through metadata service
philip.day at hp.com
Wed Jan 29 10:11:59 UTC 2014
> -----Original Message-----
> From: Justin Santa Barbara [mailto:justin at fathomdb.com]
> Sent: 28 January 2014 20:17
> To: OpenStack Development Mailing List (not for usage questions)
> Subject: Re: [openstack-dev] [Nova] bp proposal: discovery of peer instances
> through metadata service
> Thanks John - combining with the existing effort seems like the right thing to
> do (I've reached out to Claxton to coordinate). Great to see that the larger
> issues around quotas / write-once have already been agreed.
> So I propose that sharing will work in the same way, but some values are
> visible across all instances in the project. I do not think it would be
> appropriate for all entries to be shared this way. A few
> 1) A separate endpoint for shared values
> 2) Keys are shared iff e.g. they start with a prefix, like 'peers_XXX'
> 3) Keys are set the same way, but a 'shared' parameter can be passed, either
> as a query parameter or in the JSON.
> I like option #3 the best, but feedback is welcome.
> I think I will have to store the value using a system_metadata entry per
> shared key. I think this avoids issues with concurrent writes, and also makes
> it easier to have more advanced sharing policies (e.g.
> when we have hierarchical projects)
> Thank you to everyone for helping me get to what IMHO is a much better
> solution than the one I started with!
I think #1 or #3 would be fine. I don't really like #2 - doing this kind of thing through naming conventions always leads to problems IMO.
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