On 03/13/2017 09:16 AM, Sylvain Bauza wrote: > > > Le 13/03/2017 13:41, Chris Dent a écrit : >> >> From the start we've been saying that it is probably right for the >> placement service to have its own repository. This is aligned with >> the long term goal of placement being useful to many services, not >> just nova, and also helps to keep placement contained and >> comprehensible and thus maintainable. >> >> I've been worried for some time that the longer we put this off, the >> more complicated an extraction becomes. Rather than carry on >> worrying about it, I took some time over the weekend to experiment >> with a slapdash extraction to see if I could identify what would be >> the sticking points. The results are here >> >> https://github.com/cdent/placement >> >> My methodology was to lay in the basics for being able to run the >> functional (gabbi) tests and then using the failures to fix the >> code. If you read the commit log (there's only 16 commits) in >> reverse it tells a little story of what was required. >> >> All the gabbi tests are now passing (without them being changed) >> except for four that verify the response strings from exceptions. I >> didn't copy in exceptions, I created them anew to avoid copying >> unnecessary nova-isms, and didn't bother (for now) with replicating >> keyword handling. >> >> Unit tests and non-gabbi functional tests were not transferred over >> (as that would have been something more than "slapdash"). >> >> Some observations or things to think about: >> >> * Since there's only one database and all the db query code is in >> the objects, the database handling is simplified. olso_db setup >> can be used more directly. >> >> * The objects being oslo versioned objects is kind of overkill in >> this context but doesn't get too much in the way. >> >> * I collapsed the fields.ResourceClass and objects.ResourceClass >> into the same file so the latter was renamed. Doing this >> exploration made a lot of the ResourceClass handling look pretty >> complicated. Much of that complexity is because we had to deal >> with evolving through different functionality. If we built this >> functionality in a greenfield repo it could probably be more >> simple. >> >> * The FaultWrapper middleware is turned off in the WSGI stack >> because copying it over from nova would require dealing with a >> hierarchy of classes. A simplified version of it would probably >> need to be stuck back in (and apparently a gabbi test to exercise >> it, as there's not one now). >> >> * The number of requirements in the two requirements files is nicely >> small. >> >> * The scheduler report client in nova, and to a minor degree the >> filter scheduler, use some of the same exceptions and ovo.objects >> that placement uses, which presents a bit of blechiness with >> regards to code duplication. I suppose long term we could consider >> a placement-lib or something like that, except that the >> functionality provided by the same-named objects and exceptions >> are not entirely congruent. From the point of view of the external >> part of the placement API what matters are not objects, but JSON >> structures. >> >> * I've done nothing here with regard to how devstack would choose >> between the old and new placement code locations but that will be >> something to solve. It seems like it ought to be possible for two >> different sources of the placement-code to exist; just register >> one endpoint. Since we've declared that service discovery is the >> correctly and only way to find placement, this ought to be okay. >> >> I'm not sure how or if we want to proceed with this topic, but I >> think this at least allows us to talk about it with less guessing. >> My generally summary is "yeah, this is doable, without huge amounts >> of work." >> > > Please don't. > Having a separate repository would mean that deployers would need to > implement a separate package for placement plus discussing about > how/when to use it. > > For the moment, I'd rather prefer to leave operators using the placement > API by using Nova first and then after like 3 or 4 cycles, possibly > discussing with them how to cut it. > > At the moment, I think that we already have a good priority for > placement in Nova, so I don't think it's a problem to still have it in Nova.
Given that the design was always to split (eventually), and part of that means that we get to start building up a dedicated core team, I'm not sure why waiting 3 or 4 additional cycles makes sense here. I get that Pike is probably the wrong release to do this cut, given that it only *just* became mandatory. But It feels like saying this would be a Queens goal, and getting things structured in such a way that the split is easy (like any renaming of binaries, any things that should deprecate), would seem to be good goals for Pike. -Sean -- Sean Dague http://dague.net __________________________________________________________________________ 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