Open Stack

Hello operators,
we have a problem with the placement after the update of our cloud from 
Mitaka to Ocata release.

We started from a mitaka cloud and we have followed these steps: updated 
the cloud controller from Mitaka to newton, run the dbsync, updated from 
newton to ocata adding at this step the db nova_cell0 and run again the 
dbsync.  Then we have updated the compute directly from Mitaka to Ocata.

With the update to Ocata we have added the placement section in 
nova.conf, configured the related endpoint and installed the package 
openstack-nova-placement-api (placement wasn't enabled in newton)

Verifying the operation, the command nova-status upgrade check fails 
with the error

Error:
Traceback (most recent call last):
   File "/usr/lib/python2.7/site-packages/nova/cmd/status.py", line 456, 
in main
     ret = fn(*fn_args, **fn_kwargs)
   File "/usr/lib/python2.7/site-packages/nova/cmd/status.py", line 386, 
in check
     result = func(self)
   File "/usr/lib/python2.7/site-packages/nova/cmd/status.py", line 201, 
in _check_placement
     versions = self._placement_get("/")
   File "/usr/lib/python2.7/site-packages/nova/cmd/status.py", line 189, 
in _placement_get
     return client.get(path, endpoint_filter=ks_filter).json()
   File "/usr/lib/python2.7/site-packages/keystoneauth1/session.py", 
line 758, in get
     return self.request(url, 'GET', **kwargs)
   File "/usr/lib/python2.7/site-packages/positional/__init__.py", line 
101, in inner
     return wrapped(*args, **kwargs)
   File "/usr/lib/python2.7/site-packages/keystoneauth1/session.py", 
line 655, in request
     raise exceptions.from_response(resp, method, url)
ServiceUnavailable: Service Unavailable (HTTP 503)

Do you have suggestions about how to debug the problem?

Thanks a lot,
cheers,
    Federica