Actually no confusion. :-) Joe Gordon just made me realize that I didn't really explain why we had that policy.
That really should have been a follow up to my own post, not yours. Sorry if I made it look like I was arguing with you, which I wasn't.. :-) We're all good. Sean Dague http://dague.net On Oct 31, 2013 12:12 PM, "Jay Pipes" <jaypi...@gmail.com> wrote: > On 10/31/2013 11:56 AM, Sean Dague wrote: > >> On 10/31/2013 11:23 AM, Jay Pipes wrote: >> >>> On 10/31/2013 08:01 AM, Sean Dague wrote: >>> >>>> So there is a series of patches starting with - >>>> https://review.openstack.org/#**/c/53417/<https://review.openstack.org/#/c/53417/>that >>>> go back and radically >>>> change existing migration files. >>>> >>>> This is really a no-no, unless there is a critical bug fix that >>>> absolutely requires it. Changing past migrations should be considered >>>> with the same level of weight as an N-2 backport, only done when there >>>> is huge upside to the change. >>>> >>>> I've -2ed the first 2 patches in the series, though that review applies >>>> to all of them (I figured a mailing list thread was probably more useful >>>> than -2ing everything in the series). >>>> >>>> There needs to be really solid discussion about the trade offs here >>>> before contemplating something as dangerous as this. >>>> >>> >>> +1 >>> >> >> There is a very real reason why we have a firm stance on this. There are >> a huge number of OpenStack instances out in the field, at all sorts of >> different past versions. We really try to promise that you can always >> forward upgrade your database. >> >> If you go back and change an old migration, you have not forked the >> past. Some people will have already taken that migration, and they have >> one view of the world, others haven't yet, they hit your updated >> version, and they now have different database. So 2 people with Havana >> would no longer be guaranteed to have the same data model set up by us. >> >> It's easy to believe that "this change is really straight forward, it >> will be exactly the same model", but if it isn't, in any way, exactly >> the same (even in a way that we didn't realize yet that it mattered), >> you've forked the past. And that makes supporting users in these various >> forked versions of the world impossible. >> >> Migrations are basically idempotent. If you want to clean things up, do >> them in a new migration. Don't touch an old one unless it is causing >> corruption to someone's data so that fixing it with a future migration >> is not an option. >> > > LOL, I was +1'ing your thoughts, not +1'ing the proposal to have a solid > discussion about the trade-offs :) > > Sorry for the confusion! > -jay > > > ______________________________**_________________ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.**org <OpenStack-dev@lists.openstack.org> > http://lists.openstack.org/**cgi-bin/mailman/listinfo/**openstack-dev<http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev> >
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