Comment 0 for bug 1853840

If neutron is configured to support qos minimum bandwidth policy rules and the [DEFAULT]/host config option is set for both nova-compute and neutron (sriov / ovs) agents on a given compute host then neutron fails to find the compute host root resource provider and therefore fails to create the agent providers and the device providers.

Reproduction:
* deploy an all-in-one devstack with the minimum bandwidth configuration [1] and set [DEFAULT]/host for nova-compute and neutron agent to something else than the hostname of the compute host.
* start up the nova and neutron services
* check what resource providers are created during the startup

Expected:

stack@aio:~/devstack$ openstack resource provider list
+--------------------------------------+--------------------------------+------------+
| uuid | name | generation |
+--------------------------------------+--------------------------------+------------+
| 737d9a03-3f8d-4740-9b3b-933fac0dded9 | aio | 2 |
| 31b21568-8d05-5d9c-a045-6956ac62790a | aio:Open vSwitch agent | 0 |
| 1110cf59-cabf-526c-bacc-08baabbac692 | aio:Open vSwitch agent:br-test | 2 |
| 9734f92c-16da-585b-a19c-e3d4f30302fe | aio:NIC Switch agent | 0 |
+--------------------------------------+--------------------------------+------------+

Actual:
stack@aio:~/devstack$ openstack resource provider list
+--------------------------------------+--------------------------------+------------+
| uuid | name | generation |
+--------------------------------------+--------------------------------+------------+
| 737d9a03-3f8d-4740-9b3b-933fac0dded9 | aio | 2 |
+--------------------------------------+--------------------------------+------------+

There is the following log visible in the neturon-server:

Nov 22 11:39:34 aio neutron-server[14589]: DEBUG neutron.services.placement_report.plugin [None req-59a8b1b9-771b-4a38-9270-ea9fabccebb4 None None] placement: syncing state for agent type Open vSwitch agent on host not-the-compute-hostname {{(pid=14612) handle_placement_config /opt/stack/neutron/neutron/services/placement_report/plugin.py:197}}
Nov 22 11:39:34 aio neutron-server[14589]: WARNING neutron.services.placement_report.plugin [None req-59a8b1b9-771b-4a38-9270-ea9fabccebb4 None None] Synchronization of resources of agent type Open vSwitch agent at host not-the-compute-hostname to placement failed.: IndexError: list index out of range

Precieved severity:
* Medium, workaround exists: do not try to use qos configuration at the same time when the [DEFAULT]/host needs to be configured to other than the hostname of ht compute host.

[1] https://docs.openstack.org/neutron/latest/admin/config-qos-min-bw.html