openstack No valid host was found. There are not enough hosts available.

root@dell-PowerEdge-T30:~# gedit /var/log/nova/nova-conductor.log
root@dell-PowerEdge-T30:~# gedit /var/log/nova/nova-scheduler.log

\2018-03-15 14:20:35.913 1140 INFO nova.filters [req-72a6c461-d33b-4e71-a150-24c397765105 be65496d92cf4f0cad11a8f286bb64ef 9f2840ce18fe4e6889ee98f85f2fb724 - - -] Filter RetryFilter returned 0 hosts
2018-03-15 14:20:35.913 1140 INFO nova.filters [req-72a6c461-d33b-4e71-a150-24c397765105 be65496d92cf4f0cad11a8f286bb64ef 9f2840ce18fe4e6889ee98f85f2fb724 - - -] Filtering removed all hosts for the request with reservation ID 'r-x0rha8v8' and instance ID '21e45ab4-3f95-4ad7-8786-5cbf472a7209'. Filter results: ['RetryFilter: (start: 0, end: 0)']

2018-03-15 13:38:06.896 2886 WARNING nova.scheduler.utils [req-55e7065b-bdce-4aec-bbb1-49ae625ce98f be65496d92cf4f0cad11a8f286bb64ef 9f2840ce18fe4e6889ee98f85f2fb724 - - -] Failed to compute_task_build_instances: No valid host was found. There are not enough hosts available.
Traceback (most recent call last):

File "/usr/lib/python2.7/dist-packages/oslo_messaging/rpc/server.py", line 142, in inner
    return func(*args, **kwargs)

File "/usr/lib/python2.7/dist-packages/nova/scheduler/manager.py", line 84, in select_destinations
    filter_properties)

File "/usr/lib/python2.7/dist-packages/nova/scheduler/filter_scheduler.py", line 90, in select_destinations
    raise exception.NoValidHost(reason=reason)

NoValidHost: No valid host was found. There are not enough hosts available.

root@dell-PowerEdge-T30:~# gedit /etc/nova/nova.conf

scheduler_default_filters=AllHostsFilter