bandwidth resource allocation is deleted from placement during unrelated port update

[Balazs Gibizer]

Neutron deletes the bandwidth resource allocation in placement if the port is updated even though the qos policy of the port is not changed.

Reproduction:
1) Create a all in one devstack deployment from master

2) Create qos a port with qos min bandwidth policy

openstack network create net0 \
--provider-network-type vlan \
--provider-physical-network physnet0 \
--provider-segment 100 \
##
openstack subnet create subnet0 \
--network net0 \
--subnet-range 10.0.4.0/24 \
##
openstack network qos policy create qp0
openstack network qos rule create qp0 \
--type minimum-bandwidth \
--min-kbps 1000 \
--egress \
##
openstack network qos rule create qp0 \
--type minimum-bandwidth \
--min-kbps 1000 \
--ingress \
##
openstack port create port-normal-qos \
--network net0 \
--vnic-type normal \
--qos-policy qp0 \
##

3) Boot a server with that port
openstack --os-compute-api-version 2.80 server create --flavor c1 --image cirros-0.5.1-x86_64-disk --nic port-id=port-normal-qos vm1 --wait

4) Check the resource allocation of the server in placement
openstack resource provider allocation show cf5809b6-1dbe-43d5-8270-b734255a946e
+--------------------------------------+------------+--------------------------------------------------------------------------+
| resource_provider | generation | resources |
+--------------------------------------+------------+--------------------------------------------------------------------------+
| 1110cf59-cabf-526c-bacc-08baabbac692 | 13 | {'NET_BW_EGR_KILOBIT_PER_SEC': 1000, 'NET_BW_IGR_KILOBIT_PER_SEC': 1000} |
| 7b122d5c-02cd-499c-a415-c07029498010 | 21 | {'VCPU': 1, 'MEMORY_MB': 256, 'DISK_GB': 1} |
+--------------------------------------+------------+--------------------------------------------------------------------------+

5) Update the description of the port
openstack port set --description "this is my port" port-normal-qos

6) Check the resource allocation again
openstack resource provider allocation show cf5809b6-1dbe-43d5-8270-b734255a946e
+--------------------------------------+------------+---------------------------------------------+
| resource_provider | generation | resources |
+--------------------------------------+------------+---------------------------------------------+
| 7b122d5c-02cd-499c-a415-c07029498010 | 22 | {'VCPU': 1, 'MEMORY_MB': 256, 'DISK_GB': 1} |
+--------------------------------------+------------+---------------------------------------------+
Expected behavior:
The resource allocation is not changed during description update

Actual behavior:
The bandwidth resource allocation is deleted in placement

Note that changing the binding:profile also has the same effect, but changing the name of the port does not trigger the same problem.

[Balazs Gibizer (balazs-gibizer)]

As a consequence of the above problem when the server later deleted neutron fails to unbind the port so the port remains in use.

The only visible problem in the neutron log during the delete:

Oct 08 08:27:40 aio neutron-server[843]: DEBUG neutron_lib.callbacks.manager [req-61512f24-826a-424a-a866-74915d1c9d9b req-3fb1ce31-2470-4e51-b283-4928a2a87b9c service neutron] Callback neutron.services.qos.qos_plugin.QoSPlugin._check_port_for_placement_allocation_change--9223372036854757806 raised Resource provider 1110cf59-cabf-526c-bacc-08baabbac692 for cf5809b6-1dbe-43d5-8270-b734255a946e does not exist {{(pid=2968) _notify_loop /opt/stack/neutron-lib/neutron_lib/callbacks/manager.py:210}}

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/756892

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/756892
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=3605e9f82de73e0c9d3b6c8a6a99cda05bea8f4e
Submitter: Zuul
Branch: master

commit 3605e9f82de73e0c9d3b6c8a6a99cda05bea8f4e
Author: elajkat <email address hidden>
Date: Thu Oct 8 09:58:06 2020 +0200

    QoS policy update with placement: handle missing key

    Closes-Bug: #1898994
    Change-Id: Ibb826346117cd5cc824fff55d123497a19370f5c

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 18.0.0.0rc1 release candidate.