Cinder fails to automatically map availability zones to volume types

Scenario:

- Multi-AZ OpenStack deployment

$ openstack availability zone list --compute
+-----------+-------------+
| Zone Name | Zone Status |
+-----------+-------------+
| az1 | available |
| az2 | available |
| internal | available |
+-----------+-------------+

- Multiple Cinder-Ceph storage backends each available in their respective AZ

$ openstack availability zone list --volume
+-----------+---------------+
| Zone Name | Zone Status |
+-----------+---------------+
| az1 | available |
| nova | not available |
| az2 | available |
+-----------+---------------+

- Each Cinder storage back-ends is tied to a unique volume type

$ openstack volume type list --long
+--------------------------------------+-------------+-----------+---------------------+------------------------------------------------------------------------------+
| ID | Name | Is Public | Description | Properties |
+--------------------------------------+-------------+-----------+---------------------+------------------------------------------------------------------------------+
| 84acc1d5-4a83-45b4-b4bd-beb9bd655c0c | ssd | True | None | RESKEY:availability_zones='nova,az2', volume_backend_name='cinder-ceph-ssd' |
| 332299a5-4b68-4663-b316-1df9735646a8 | nvme | True | None | RESKEY:availability_zones='nova,az1', volume_backend_name='cinder-ceph-nvme' |
| 07fc3552-b546-4eeb-ba4a-08d0b03c5c1b | __DEFAULT__ | True | Default Volume Type | |
+--------------------------------------+-------------+-----------+---------------------+------------------------------------------------------------------------------+

$ openstack volume service list --long | grep -v disabled
+------------------+--------------------------------------+------+----------+-------+----------------------------+-----------------+
| Binary | Host | Zone | Status | State | Updated At | Disabled Reason |
+------------------+--------------------------------------+------+----------+-------+----------------------------+-----------------+
| cinder-backup | cinder | nova | enabled | up | 2022-12-15T02:15:19.000000 | None |
| cinder-volume | cinder@cinder-ceph-nvme | az1 | enabled | up | 2022-12-15T02:15:19.000000 | None |
| cinder-scheduler | cinder | nova | enabled | up | 2022-12-15T02:15:23.000000 | None |
| cinder-volume | cinder@cinder-ceph-ssd | az2 | enabled | up | 2022-12-15T02:15:24.000000 | None |
+------------------+--------------------------------------+------+----------+-------+----------------------------+-----------------+

Nova Cloud Controller has been configured to disallow volume cross-az-attach, otherwise volumes will be created in an inaccessible availability zone

$ juju config nova-cloud-controller cross-az-attach=false

Cinder should be able to calculate respective volume types when a respective AZ is specified, however it fails to create volumes:

$ openstack volume create --availability-zone az2 --size 10 az2-volume-test
Availability zone 'az2' is invalid. (HTTP 400) (Request-ID: req-4a4ce41d-cf57-4157-8c4b-2cad8edd28aa)

Setting these juju configurations does not make a difference:

$ juju config cinder-ceph-ssd backend-availability-zone=az2
$ juju config cinder-ceph-nvme backend-availability-zone=az1

Tracing the process shows that the issue is related to _get_volume_type() call in the _extract_availability_zones() function (trace log attached).

Looking into _get_volume_type(), it appears to be missing the logic to calculate proper volume types matching avalability zones defined with RESKEY:availability_zones.

I made a small patch that addresses that issue (attached).

Once the patch is applied, volumes are properly created mapping correctly to correct volume types:

$ openstack volume create --availability-zone az2 --size 10 az2-volume-test
+---------------------+--------------------------------------+
| Field | Value |
+---------------------+--------------------------------------+
| attachments | [] |
| availability_zone | az2 |
| bootable | false |
| consistencygroup_id | None |
| created_at | 2022-12-15T02:24:24.516545 |
| description | None |
| encrypted | False |
| id | 0d78adb5-aa4f-42a1-ab75-902603ff8d51 |
| migration_status | None |
| multiattach | False |
| name | az2-volume-test |
| properties | |
| replication_status | None |
| size | 10 |
| snapshot_id | None |
| source_volid | None |
| status | creating |
| type | ssd |
| updated_at | None |
| user_id | e40ba17bc77c462baa57b1f578b9b719 |
+---------------------+--------------------------------------+