This couldn't be reproduced in upstream Nautilus (v14) with vstart Cephfs (2xMDS), so perhaps this could be a downstream-only issue.
Traceback found in ceph-mgr log:
"Traceback (most recent call last):
File "/lib/python3.6/site-packages/cherrypy/_cprequest.py", line 670, in respond
response.body = self.handler()
File "/lib/python3.6/site-packages/cherrypy/lib/encoding.py", line 220, in __call__
self.body = self.oldhandler(*args, **kwargs)
File "/lib/python3.6/site-packages/cherrypy/_cptools.py", line 237, in wrap
return self.newhandler(innerfunc, *args, **kwargs)
File "/usr/share/ceph/mgr/dashboard/services/exception.py", line 88, in dashboard_exception_handler
return handler(*args, **kwargs)
File "/lib/python3.6/site-packages/cherrypy/_cpdispatch.py", line 60, in __call__
return self.callable(*self.args, **self.kwargs)
File "/usr/share/ceph/mgr/dashboard/controllers/__init__.py", line 649, in inner
ret = func(*args, **kwargs)
File "/usr/share/ceph/mgr/dashboard/controllers/__init__.py", line 842, in wrapper
return func(*vpath, **params)
File "/usr/share/ceph/mgr/dashboard/controllers/cephfs.py", line 32, in get
File "/usr/share/ceph/mgr/dashboard/controllers/cephfs.py", line 159, in fs_status
AttributeError: 'NoneType' object has no attribute 'get'
Additionally, downstream Mgr API mgr.list_servers() shows 'mds.0' detached from any host (while upstream one properly displays 'mds.a' attached to its host).
*** Bug 1772788 has been marked as a duplicate of this bug. ***
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.