neutron-ovn-db-sync-util stops with Traceback due to L3 service plugin expecting ``ovn`` mech driver to be present while ``ovn-sync`` mech driver is loaded

[Frode Nordahl]

The ``neutron-ovn-db-sync-util`` overrides the mechanism driver to be ``ovn-sync``[0]. Subsequently it calls into the OVN L3 service plugin [1] which expects the ``ovn`` mechanism driver to be present [2].

Do we need both mechanism drivers there, does the OVN L3 service plugin need to check for both or do we need a way to tell the service plugin which mechanism driver to use?

2020-06-05 07:33:11.005 1486514 CRITICAL neutron_ovn_db_sync_util [req-3c6fb887-7610-466c-adfb-07b6404475c1 - - - - -] Unhandled error: KeyError: 'ovn'
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util Traceback (most recent call last):
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util File "/usr/bin/neutron-ovn-db-sync-util", line 10, in <module>
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util sys.exit(main())
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util File "/usr/lib/python3/dist-packages/neutron/cmd/ovn/neutron_ovn_db_sync_util.py", line 221, in main
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util sb_synchronizer.do_sync()
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util File "/usr/lib/python3/dist-packages/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_db_sync.py", line 1215, in do_sync
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util self.l3_plugin.schedule_unhosted_gateways()
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util File "/usr/lib/python3/dist-packages/neutron/services/ovn_l3/plugin.py", line 340, in schedule_unhosted_gateways
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util chassis_with_physnets = self._sb_ovn.get_chassis_and_physnets()
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util File "/usr/lib/python3/dist-packages/neutron/services/ovn_l3/plugin.py", line 97, in _sb_ovn
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util return self._plugin_driver.sb_ovn
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util File "/usr/lib/python3/dist-packages/neutron/services/ovn_l3/plugin.py", line 108, in _plugin_driver
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util self._mech = self._plugin.mechanism_manager.mech_drivers['ovn'].obj
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util KeyError: 'ovn'
2020-06-05 07:33:11.005 1486514 ERROR neutron_ovn_db_sync_util

0: https://github.com/openstack/neutron/blob/c6e5e119b84a7d55e539509050ce56236ebf57c6/neutron/cmd/ovn/neutron_ovn_db_sync_util.py#L188
1: https://github.com/openstack/neutron/blob/c6e5e119b84a7d55e539509050ce56236ebf57c6/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_db_sync.py#L1213
2: https://github.com/openstack/neutron/blob/ef97c83e8753a668e0c0f405ef4beb027efa02cd/neutron/services/ovn_l3/plugin.py#L108

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/733775

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/733775
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=206ce246768d6fb04b6bd92e189188f6702c74a7
Submitter: Zuul
Branch: master

commit 206ce246768d6fb04b6bd92e189188f6702c74a7
Author: Frode Nordahl <email address hidden>
Date: Fri Jun 5 09:52:48 2020 +0200

    [OVN] Allow use of ovn-sync mechanism driver

    The ``neutron-ovn-db-sync-util`` replaces the ``ovn`` mechanism
    driver with the ``ovn-sync`` mechanism driver. Subsequently it
    makes calls into the OVN L3 service plugin.

    At present the OVN L3 service plugin assumes the ``ovn`` mechanism
    driver to be present and produces a Traceback when it is not.

    This patch fixes that by testing for both of the supported
    mechanism drivers.

    Change-Id: I1ac685a12f49119f5ef1428cbc504b639d783803
    Closes-Bug: #1882202
    Signed-off-by: Frode Nordahl <email address hidden>

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/ussuri
Review: https://review.opendev.org/738961

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/738961
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=ce2866a4f6c6ee06e835f19394c1dd02ef83cff5
Submitter: Zuul
Branch: stable/ussuri

commit ce2866a4f6c6ee06e835f19394c1dd02ef83cff5
Author: Frode Nordahl <email address hidden>
Date: Fri Jun 5 09:52:48 2020 +0200

    [OVN] Allow use of ovn-sync mechanism driver

    The ``neutron-ovn-db-sync-util`` replaces the ``ovn`` mechanism
    driver with the ``ovn-sync`` mechanism driver. Subsequently it
    makes calls into the OVN L3 service plugin.

    At present the OVN L3 service plugin assumes the ``ovn`` mechanism
    driver to be present and produces a Traceback when it is not.

    This patch fixes that by testing for both of the supported
    mechanism drivers.

    Change-Id: I1ac685a12f49119f5ef1428cbc504b639d783803
    Closes-Bug: #1882202
    Signed-off-by: Frode Nordahl <email address hidden>
    (cherry picked from commit 206ce246768d6fb04b6bd92e189188f6702c74a7)