Comment 3 for bug 1803522

It also seems this error can happen directly after deployment:

2018-11-16 14:44:18,664 [249780] ERROR cotyledon._utils: Unhandled exception
Traceback (most recent call last):
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/cotyledon/_utils.py", line 95, in exit_on_exception
    yield
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/cotyledon/_service.py", line 139, in _run
    self.run()
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/gnocchi/cli/metricd.py", line 78, in run
    self._configure()
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/tenacity/__init__.py", line 241, in wrapped_f
    return self.call(f, *args, **kw)
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/tenacity/__init__.py", line 330, in call
    start_time=start_time)
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/tenacity/__init__.py", line 279, in iter
    return fut.result()
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/concurrent/futures/_base.py", line 455, in result
    return self.__get_result()
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/tenacity/__init__.py", line 333, in call
    result = fn(*args, **kwargs)
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/gnocchi/cli/metricd.py", line 162, in _configure
    self.fallback_tasks = list(self.incoming.iter_sacks())
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/gnocchi/incoming/__init__.py", line 248, in iter_sacks
    return (self._make_sack(i) for i in six.moves.range(self.NUM_SACKS))
  File "/var/lib/kolla/venv/local/lib/python2.7/site-packages/gnocchi/incoming/__init__.py", line 119, in NUM_SACKS
    raise SackDetectionError(e)
SackDetectionError: int() argument must be a string or a number, not 'NoneType'

It is solved by running gnocchi-update.