Cinder's v1 API was removed in queens, but it was necessary to retain its associated "volume" service in order to work around a bug in the queens-era tempest code. See [1] for details.
[1] https://review.opendev.org/649084
The problem is this legacy "volume" service causes tripleo's keystone endpoint validation to fail after performing an FFU from queens to train. The FFU will succeed, but subsequent attempts to update the stack will fail like this:
TASK [tripleo-keystone-resources : Check Keystone public endpoint status] ******
Sunday 13 September 2020 11:14:39 +0000 (0:00:05.000) 0:25:13.826 ******
...
failed: [undercloud] (item={'started': 1, 'finished': 0, 'ansible_job_id': '668760418547.976504', 'results_file': '/root/.ansible_async/668760418547.976504', 'changed': True, 'failed': False, 'tripleo_keystone_resources_data': {'key': 'cinderv3', 'value': {'endpoints': {'admin': 'http://172.17.1.x:8776/v3/%(tenant_id)s', 'internal': 'http://172.17.1.x:8776/v3/%(tenant_id)s', 'public': 'http://10.0.0.x:8776/v3/%(tenant_id)s'}, 'region': 'regionOne', 'service': 'volumev3', 'users': {'cinderv3': {'password': 'blah', 'roles': ['admin', 'service']}}}}, 'ansible_loop_var': 'tripleo_keystone_resources_data'}) => {"ansible_job_id": "668760418547.976504", "ansible_loop_var": "tripleo_keystone_resources_endpoint_async_result_item", "attempts": 1, "changed": false, "finished": 1, "msg": "Multiple matches found for cinderv3", "tripleo_keystone_resources_endpoint_async_result_item": {"ansible_job_id": "668760418547.976504", "ansible_loop_var": "tripleo_keystone_resources_data", "changed": true, "failed": false, "finished": 0, "results_file": "/root/.ansible_async/668760418547.976504", "started": 1, "tripleo_keystone_resources_data": {"key": "cinderv3", "value": {"endpoints": {"admin": "http://172.17.1.x:8776/v3/%(tenant_id)s", "internal": "http://172.17.1.x:8776/v3/%(tenant_id)s", "public": "http://10.0.0.x:8776/v3/%(tenant_id)s"}, "region": "regionOne", "service": "volumev3", "users": {"cinderv3": {"password": "blah", "roles": ["admin", "service"]}}}}}}
The problem can be worked around by deleting the "volume" service, which also removes its associated endpoints.
Fix proposed to branch: master
Review: https:/