环境说明：
| openstack版本 | pike |
| 控制节点主机 | openstack-controller（ubuntu 16.04.5） |
| 计算节点主机 | openstack-computer（ubuntu 16.04.5） |
| 镜像 | cirros |
报错信息：
新建实例dt01报错：Host 'openstack-computer' is not mapped to any cell
问题解决办法：
控制节点以stack用户执行如下命令：
stack@openstack-controller:~$ nova-manage cell_v2 discover_hosts --verbose
Option "logdir" from group "DEFAULT" is deprecated. Use option "log-dir" from group "DEFAULT".
/usr/local/lib/python2.7/dist-packages/pymysql/cursors.py:166: Warning: (1287, u"'@@tx_isolation' is deprecated and will be removed in a future release. Please use '@@transaction_isolation' instead")
result = self._query(query)
Found 2 cell mappings.
Skipping cell0 since it does not contain hosts.
Getting computes from cell 'cell1': da859b66-f993-4b79-ac58-58009ad27bea
Found 0 unmapped computes in cell: da859b66-f993-4b79-ac58-58009ad27bea
重建实例：
再次新建实例dt04：
实例创建成功，且实例位于openstack-computer节点。
至此问题解决。
参考：https://ask.openstack.org/en/question/116517/host-is-not-mapped-to-any-cell/
https://docs.openstack.org/nova/latest/user/cells.html#step-by-step-for-common-use-cases