pre-cells_v2 nova-osapi_compute service in database breaks instance lookup

The code in [1] was added in Newton, and I think we'd be OK to add a warning if you're not using cells v1 and the osapi_compute minimum version is < 15 in that code as a breadcrumb at least, and we could backport that through to queens, pike and ocata.

For nova-status, we'd likely add a check that queries the minimum nova-osapi_compute service version across all cells (API services should really only be in once cell though) and if < 15 we'd emit a warning. The thing about the nova-status check would be, if you had older nova-osapi_compute services in your nova (cell) database from before upgrading to ocata where cells v2 was required, and then you re-configured the API to point the [database]/connection at the nova_cell0 database and created a new 'current' service version, the cross-cell min version check would give a warning for a cell table entry you don't actually care about. The resolution would just be to delete that entry though I think. Alternatively, we could just not look across cells in nova-status and just rely on [database]/connection being set (or at least look in cell0).

Fix proposed to branch: master
Review: https://review.openstack.org/557506

Reviewed: https://review.openstack.org/557506
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=eaf6340847c35ace3b4b681a95b8a79a7a3f2491
Submitter: Zuul
Branch: master

commit eaf6340847c35ace3b4b681a95b8a79a7a3f2491
Author: Matt Riedemann <email address hidden>
Date: Wed Mar 28 16:26:48 2018 -0400

    Log a warning and add nova-status check for old API service versions

    Change Ib984c30543acb3ca9cb95fb53d44d9ded0f5a5c8, which was added
    in Newton when cells v2 was optional, added some transitional code
    to the API for looking up an instance, which didn't rely on instance
    mappings in a cell to find the instance if the minimum nova-osapi_compute
    service version was from before Ocata.

    People have reported this being a source of confusion when upgrading
    from before Ocata, when cells v2 wasn't required, to Ocata+ where cells
    v2 along with the mapping setup is required. That's because they might
    have older nova-osapi_compute service version records in their 'nova'
    (cell) database which makes the API think the code is older than it
    actually is, and results in an InstanceNotFound error.

    This change does two things:

    1. Adds a warning to the compute API code in this scenario to serve
       as a breadcrumb if a deployment hits this issue.

    2. A nova-status check to look for minimum nova-osapi_compute service
       versions across all cells and report the issue as a warning. It's
       not an upgrade failure since we don't know how the nova-api service
       is configured, but leave that investigation up to the deployer.

    This is also written in such a way that we should be able to backport
    this through to stable/ocata.

    Change-Id: Ie2bc4616439352850cf29a9de7d33a06c8f7c2b8
    Closes-Bug: #1759316

This issue was fixed in the openstack/nova 18.0.0.0b1 development milestone.

Fix proposed to branch: stable/queens
Review: https://review.openstack.org/563251

Reviewed: https://review.openstack.org/563251
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=aaa259d9d34bab4fd168111b7393c000f7b82077
Submitter: Zuul
Branch: stable/queens

commit aaa259d9d34bab4fd168111b7393c000f7b82077
Author: Matt Riedemann <email address hidden>
Date: Wed Mar 28 16:26:48 2018 -0400

    Log a warning and add nova-status check for old API service versions

    Change Ib984c30543acb3ca9cb95fb53d44d9ded0f5a5c8, which was added
    in Newton when cells v2 was optional, added some transitional code
    to the API for looking up an instance, which didn't rely on instance
    mappings in a cell to find the instance if the minimum nova-osapi_compute
    service version was from before Ocata.

    People have reported this being a source of confusion when upgrading
    from before Ocata, when cells v2 wasn't required, to Ocata+ where cells
    v2 along with the mapping setup is required. That's because they might
    have older nova-osapi_compute service version records in their 'nova'
    (cell) database which makes the API think the code is older than it
    actually is, and results in an InstanceNotFound error.

    This change does two things:

    1. Adds a warning to the compute API code in this scenario to serve
       as a breadcrumb if a deployment hits this issue.

    2. A nova-status check to look for minimum nova-osapi_compute service
       versions across all cells and report the issue as a warning. It's
       not an upgrade failure since we don't know how the nova-api service
       is configured, but leave that investigation up to the deployer.

    This is also written in such a way that we should be able to backport
    this through to stable/ocata.

    Conflicts:
          doc/source/cli/nova-status.rst

    NOTE(mriedem): The conflict is because the Rocky section
    in the man page does not exist in Queens. The note about
    the new check is added to the Queens section and mentions
    it was backported from Rocky.

    Change-Id: Ie2bc4616439352850cf29a9de7d33a06c8f7c2b8
    Closes-Bug: #1759316
    (cherry picked from commit eaf6340847c35ace3b4b681a95b8a79a7a3f2491)

This issue was fixed in the openstack/nova 17.0.5 release.