Comment 1 for bug 1944043

The following traceback was captured in stable/train base deployment.
In this case 504 is returned from cinder API instead of 503 but the traceback shows that cinderclient.exceptions.ClientException is raised when API call fails.

~~~
2021-09-09 12:11:14.000 7 INFO nova.compute.manager [req-d4ea1834-53a1-4786-8c9a-f495307ec9d3 99f5628a6a55449fae14d97881a054ce e722c8ab654a440e8d3cdc5ef592f21b - default default] [instance: 3a9b54b5-35b7-4427-bc64-f88b0d8949b3] Detaching volume 35ff73cd-ebe2-40b3-8be6-f91aca202aa8
...
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server [req-d4ea1834-53a1-4786-8c9a-f495307ec9d3 99f5628a6a55449fae14d97881a054ce e722c8ab654a440e8d3cdc5ef592f21b - default default] Exception during message handling: cinderclient.excep
tions.ClientException: Gateway Timeout (HTTP 504)
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server Traceback (most recent call last):
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server File "/usr/lib/python3.6/site-packages/oslo_messaging/rpc/server.py", line 165, in _process_incoming
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server res = self.dispatcher.dispatch(message)
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server File "/usr/lib/python3.6/site-packages/oslo_messaging/rpc/dispatcher.py", line 274, in dispatch
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server return self._do_dispatch(endpoint, method, ctxt, args)
...
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server File "/usr/lib/python3.6/site-packages/nova/compute/manager.py", line 6237, in _detach_volume
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server attachment_id=attachment_id, destroy_bdm=destroy_bdm)
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server File "/usr/lib/python3.6/site-packages/nova/virt/block_device.py", line 486, in detach
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server attachment_id, destroy_bdm)
...
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server File "/usr/lib/python3.6/site-packages/cinderclient/client.py", line 223, in delete
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server return self._cs_request(url, 'DELETE', **kwargs)
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server File "/usr/lib/python3.6/site-packages/cinderclient/client.py", line 205, in _cs_request
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server return self.request(url, method, **kwargs)
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server File "/usr/lib/python3.6/site-packages/cinderclient/client.py", line 191, in request
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server raise exceptions.from_response(resp, body)
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server cinderclient.exceptions.ClientException: Gateway Timeout (HTTP 504)
2021-09-09 12:12:14.512 7 ERROR oslo_messaging.rpc.server
~~~