[openstack-dev] [nova] Required data migrations in Kilo, need Turbo Hipster tests updated

Michael Still mikal at stillhq.com
Thu Apr 23 00:44:51 UTC 2015

On Thu, Apr 23, 2015 at 1:31 AM, Dan Smith <dms at danplanet.com> wrote:
>> Sure, but for people doing continuous deployment, they clearly haven't
>> ran the migrate_flavor_data (or if they have, they haven't filed any
>> bugs about it not working[0]).
> Hence the usefulness of T-H here, right? The point of the migration
> check is to make sure that people _do_ run it before the leave kilo.
> Right now, they have nothing other than the big note in the release
> notes about doing it. Evidence seems to show that they're not seeing it,
> which is exactly why we need the check :)
>> I also found what I believe to be a bug with the flavor migration code.
>> I started working on a fix by my limited knowledge of nova's objects has
>> hindered me. Any thoughts on the legitimacy of the bug would be helpful
>> though: https://bugs.launchpad.net/nova/+bug/1447132 . Basically for
>> some of the datasets that turbo-hipster uses there are no entries in the
>> new instance_extra table stopping any flavor migration from actually
>> running. Then in your change (174480) you check the metadata table
>> instead of the extras table causing the migration to fail even though
>> migrate_flavor_data thinks there is nothing to do.
> I don't think this has anything to do with the objects, it's probably
> just a result of my lack of sqlalchemy-fu. Sounds like you weren't close
> to a fix, so I'll try to cook something up.
> So, a question here: These data sets were captured at some point in
> time, right? Does that mean that they were from say Icehouse era and
> have had nothing done to them since? Meaning, are there data sets that
> actually had juno or kilo running on them? This instance_extra thing
> would be the case for any instance that hasn't been touched in a long
> time, so it's legit. However, as we move to more online migration of
> data, I do wonder if taking an ancient dataset, doing schema migrations
> forward to current and then expecting it to work is really reflective of
> reality.

That is correct -- these are icehouse datasets which have been
upgraded, but never had an juno run against them. It would be hard for
turbo hipster to do anything else, as it doesn't actually run a cloud.
We can explore ideas around how to run live upgrade code, but its
probably a project to pursue separately.

One quick option here is I can reach out and ask our dataset donors if
they have more recent dumps they'd be willing to share.

> Can you shed some light on what is really going on?
>> I think it's worth noting that your change (174480) will require
>> operators (particularly continuous deployers) to run migrate_flavor_data
>> and given the difficulties I've found I'm not sure it's ready to be ran.
> Right, that's the point.
>> If we encounter bugs against real datasets with migrate_flavor_data then
>> deployers will be unable to upgrade until migrate_flavor_data is fixed.
>> This may make things awkward if a deployer updates their codebase and
>> can't run the migrations. Clearly they'll have to roll-back the changes.
>> This is the scenario turbo-hipster is meant to catch - migrations that
>> don't work on real datasets.
> Right, that's why we're holding until we make sure that it works.
>> If migrate_flavor_data is broken a backport into Kilo will be needed so
>> that if Liberty requires all the flavor migrations to be finished they
>> can indeed be ran before upgrading to Liberty. This may give reason not
>> to block on having the flavors migrated until the M-release but I
>> realise that has other undersiable consequences (ie high code maintenance).
> Backports to fix this are fine IMHO, and just like any other bug found
> in actual running of things. It's too bad that none of our continuous
> deployment people seem to have found this yet, but that's a not uncommon
> occurrence. Obviously if we hit something that makes it too painful to
> get right in kilo, then we can punt for another cycle.
> Thanks!


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