[nova][kolla] questions on cells

Mark Goddard mark at stackhpc.com
Thu Oct 3 08:24:10 UTC 2019


On Wed, 2 Oct 2019 at 14:48, Matt Riedemann <mriedemos at gmail.com> wrote:
>
> On 10/1/2019 5:00 AM, Mark Goddard wrote:
> >>> 5. What DB configuration should be used in nova.conf when running
> >>> online data migrations? I can see some migrations that seem to need
> >>> the API DB, and others that need a cell DB. If I just give it the API
> >>> DB, will it use the cell mappings to get to each cell DB, or do I need
> >>> to run it once for each cell?
> >> The API DB has its own set of migrations, so you obviously need API DB
> >> connection info to make that happen. There is no fanout to all the rest
> >> of the cells (currently), so you need to run it with a conf file
> >> pointing to the cell, for each cell you have. The latest attempt
> >> at making this fan out was abanoned in July with no explanation, so it
> >> dropped off my radar at least.
> > That makes sense. The rolling upgrade docs could be a little clearer
> > for multi-cell deployments here.
> >
>
> This recently merged, hopefully it helps clarify:
>
> https://review.opendev.org/#/c/671298/

It does help a little for the schema migrations, but the point was
about data migrations.

>
> >>> 6. After an upgrade, when can we restart services to unpin the compute
> >>> RPC version? Looking at the compute RPC API, it looks like the super
> >>> conductor will remain pinned until all computes have been upgraded.
> >>> For a cell conductor, it looks like I could restart it to unpin after
> >>> upgrading all computes in that cell, correct?
> >> Yeah.
> >>
> >>> 7. Which services require policy.{yml,json}? I can see policy
> >>> referenced in API, conductor and compute.
> >> That's a good question. I would have thought it was just API, so maybe
> >> someone else can chime in here, although it's not specific to cells.
> > Yeah, unrelated to cells, just something I wondered while digging
> > through our nova Ansible role.
> >
> > Here is the line that made me think policies are required in
> > conductors:https://opendev.org/openstack/nova/src/commit/6d5fdb4ef4dc3e5f40298e751d966ca54b2ae902/nova/compute/api.py#L666.
> > I guess this is only required for cell conductors though?
> >
>
> That is not the conductor service, it's the API.

My mistake, still learning the flow of communication.

>
> --
>
> Thanks,
>
> Matt
>



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