Backport: l3_agent_scheduler AZLeastRoutersScheduler TypeError

[LIU Yulong]

This bug was reported for mitaka/liberty release.

There already has a fixed bug here:
https://bugs.launchpad.net/neutron/+bug/1641879

But the original patch which caused this bug was backported to mitaka and liberty.
https://review.openstack.org/#/q/9f30df85fe78d830331a43fa29fc2d83708c861d

Traces:
http://paste.openstack.org/show/593939/

How to reproduce:
1. Upgrade neutron to 8.3.0 (current stable/mitaka version)
2. router_scheduler_driver = neutron.scheduler.l3_agent_scheduler.AZLeastRoutersScheduler

[Boden R (boden)]

Just to confirm; this bug is for the backport of fix in [1] to the mitaka/liberty branches since that wasn't done as part of the patch in [1]? Is this correct?

[1] https://bugs.launchpad.net/neutron/+bug/1641879

[LIU Yulong (dragon889)]

Hi, Boden,
yes, this bug was reported for mitaka/liberty release.
Upstream master fix was done here: https://review.openstack.org/#/c/400233
Current newton backport is still blocked: https://review.openstack.org/#/c/400192
And no backport patches for mitaka or liberty.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: stable/mitaka
Review: https://review.openstack.org/418644

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/418644
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=dd6fd625391d310040118ae5c3575ff6cff6e833
Submitter: Jenkins
Branch: stable/mitaka

commit dd6fd625391d310040118ae5c3575ff6cff6e833
Author: Pepijn Oomen <email address hidden>
Date: Mon Nov 21 12:07:45 2016 +0100

    Solve unexpected NoneType returned by _get_routers_can_schedule.

    Solve a problem with an unexpected NoneType returned by
    _get_routers_can_schedule called from within
    _schedule_ha_routers_to_additional_agent when using:

    router_scheduler_driver =
        neutron.scheduler.l3_agent_scheduler.AZLeastRoutersScheduler

    This was leading to problems with starting neutron-l3-agent on network
    nodes, causing HA routers to fail to start.

    Closes-Bug: #1641879
    Related-Bug: #1654128
    Change-Id: I33c5a6214670f0ada9c2293b0eb2ff243f6f7b1b
    (cherry picked from commit 62176a9b40619327aacee9ed4162252d1245d019)