instance or volume creation fails with "Error: error connecting to the cluster: error code 95" in cinder volume log

Issue

• instance or volume creation fails with "Error: error connecting to the cluster: error code 95" in cinder volume log

• Error logs in /var/log/cinder/volume.log :

018-05-17 12:17:57.544 126770 ERROR cinder.volume.drivers.rbd Traceback (most recent call last):
2018-05-17 12:17:57.544 126770 ERROR cinder.volume.drivers.rbd   File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/rbd.py", line 321, in _do_conn
2018-05-17 12:17:57.544 126770 ERROR cinder.volume.drivers.rbd     client.connect()
2018-05-17 12:17:57.544 126770 ERROR cinder.volume.drivers.rbd   File "rados.pyx", line 785, in rados.Rados.connect (rados.c:8969)
2018-05-17 12:17:57.544 126770 ERROR cinder.volume.drivers.rbd Error: error connecting to the cluster: error code 95
2018-05-17 12:17:57.544 126770 ERROR cinder.volume.drivers.rbd 
2018-05-17 12:18:07.585 126770 ERROR cinder.volume.drivers.rbd [req-996f73c6-cdce-497f-a56e-4fcc87a1b7f8 - - - - -] Error connecting to ceph cluster.: Error: error connecting to 
the cluster: error code 95
2018-05-17 12:18:07.585 126770 ERROR cinder.volume.drivers.rbd Traceback (most recent call last):
2018-05-17 12:18:07.585 126770 ERROR cinder.volume.drivers.rbd   File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/rbd.py", line 321, in _do_conn
2018-05-17 12:18:07.585 126770 ERROR cinder.volume.drivers.rbd     client.connect()
2018-05-17 12:18:07.585 126770 ERROR cinder.volume.drivers.rbd   File "rados.pyx", line 785, in rados.Rados.connect (rados.c:8969)
2018-05-17 12:18:07.585 126770 ERROR cinder.volume.drivers.rbd Error: error connecting to the cluster: error code 95
2018-05-17 12:18:07.585 126770 ERROR cinder.volume.drivers.rbd 
2018-05-17 12:18:27.624 126770 ERROR cinder.volume.drivers.rbd [req-996f73c6-cdce-497f-a56e-4fcc87a1b7f8 - - - - -] Error connecting to ceph cluster.: Error: error connecting to 
the cluster: error code 95
2018-05-17 12:18:27.624 126770 ERROR cinder.volume.drivers.rbd Traceback (most recent call last):
2018-05-17 12:18:27.624 126770 ERROR cinder.volume.drivers.rbd   File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/rbd.py", line 321, in _do_conn
2018-05-17 12:18:27.624 126770 ERROR cinder.volume.drivers.rbd     client.connect()
2018-05-17 12:18:27.624 126770 ERROR cinder.volume.drivers.rbd   File "rados.pyx", line 785, in rados.Rados.connect (rados.c:8969)
2018-05-17 12:18:27.624 126770 ERROR cinder.volume.drivers.rbd Error: error connecting to the cluster: error code 95
2018-05-17 12:18:27.624 126770 ERROR cinder.volume.drivers.rbd 



2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager [req-996f73c6-cdce-497f-a56e-4fcc87a1b7f8 - - - - -] Failed to initialize driver.: VolumeBackendAPIException: Bad or un
expected response from the storage volume backend API: Error connecting to ceph cluster.
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager Traceback (most recent call last):
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/volume/manager.py", line 431, in init_host
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     self.driver.check_for_setup_error()
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/rbd.py", line 272, in check_for_setup_error
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     with RADOSClient(self):
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/rbd.py", line 154, in __init__
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     self.cluster, self.ioctx = driver._connect_to_rados(pool)
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/rbd.py", line 330, in _connect_to_rados
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     return _do_conn(pool, remote, timeout)
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/utils.py", line 799, in _wrapper
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     return r.call(f, *args, **kwargs)
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/retrying.py", line 229, in call
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     raise attempt.get()
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/retrying.py", line 261, in get
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     six.reraise(self.value[0], self.value[1], self.value[2])
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/retrying.py", line 217, in call
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     attempt = Attempt(fn(*args, **kwargs), attempt_number, False)
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/rbd.py", line 328, in _do_conn
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager     raise exception.VolumeBackendAPIException(data=msg)
2018-05-17 12:18:27.627 126770 ERROR cinder.volume.manager VolumeBackendAPIException: Bad or unexpected response from the storage volume backend API: Error connecting to ceph clu
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