Comment 1 for bug 1812935

Some debug informations to move a little bit forward on this topic...

The exception is raised inside the nova-conductor container.

The problem seems to occur when the cache is enable and the backend used is oslo.cache.

Config in use in /var/lib/config-data/puppet-generated/nova/etc/nova/nova.conf :
backend=oslo_cache.memcache_pool
enabled=True
debug_cache_backend=True

Nova services seems to be unregister:
$ openstack compute service list
+----+--------+------+------+--------+-------+------------+-----------------+-------------+ │·| Id | Binary | Host | Zone | Status | State | Updated_at | Disabled Reason | Forced down | │·
+----+--------+------+------+--------+-------+------------+-----------------+-------------+ │·+----+--------+------+------+--------+-------+------------+-----------------+-------------+

Else when the cache is disable the previous command return results
[stack@win1 ~]$ openstack compute service list
+----+------------------+------------------+----------+---------+-------+----------------------------+
| ID | Binary | Host | Zone | Status | State | Updated At |
+----+------------------+------------------+----------+---------+-------+----------------------------+
| 1 | nova-conductor | win1.localdomain | internal | enabled | up | 2019-01-24T16:07:47.000000 |
| 2 | nova-consoleauth | win1.localdomain | internal | enabled | up | 2019-01-24T16:07:41.000000 |
| 3 | nova-scheduler | win1.localdomain | internal | enabled | up | 2019-01-24T16:07:43.000000 |
| 8 | nova-compute | win1.localdomain | nova | enabled | up | 2019-01-24T16:07:47.000000 |
+----+------------------+------------------+----------+---------+-------+----------------------------+

Same problem when we use `nova service-list`