reinstalling a compute node and then upgrading from pike to queens fails

Hi,

I had a working xenial/pike cloud recently, using neutron-ovs, with some compute nodes, in particular a ppc64 compute node named bagon. I needed to reinstall it, so I did the following :

1. nova service-delete <id of the compute service on bagon>
2. neutron agent-delete <uuid of the openvswitch agent on bagon>
3. Re-commission the node and deploy the nova-compute application on it

After what, some times later, I upgraded the cloud to queens. This apparently caused the node to stop working. It was logging the following error (nova-compute.log on bagon) :

2018-04-09 06:25:26.099 128068 ERROR nova.scheduler.client.report [req-f1eebe14-fcfb-4878-b557-50105790d3b5 6bd667e324ea463abaacbc1f9c3bbed3 95cafd7ede504ef6b7b67ead691d3883 - default default] [req-29de76b9-50c2-4bff-85a9-363d665c250f] Failed to create resource provider record in placement API for UUID 2d236848-df06-47f1-92a4-a1afefe62931. Got 409: {"errors": [{"status": 409, "request_id": "req-29de76b9-50c2-4bff-85a9-363d665c250f", "detail": "There was a conflict when trying to complete your request.\n\n Conflicting resource provider name: bagon.fqdn already exists. ", "title": "Conflict"}]}.

Full stack trace : https://pastebin.canonical.com/p/ynhpgsB8bp/ (sorry, Canonical-only link)

I tracked down the problem, and found it was due to the following mismatch :

mysql> select uuid,host,deleted from compute_nodes where host='bagon';
+--------------------------------------+-------+---------+
| uuid | host | deleted |
+--------------------------------------+-------+---------+
| 2d236848-df06-47f1-92a4-a1afefe62931 | bagon | 0 |
| 92232041-9767-466b-a82f-20ecef0af6fa | bagon | 9 |
+--------------------------------------+-------+---------+
2 rows in set (0.00 sec)

mysql> use nova_api;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select uuid,name from resource_providers where name like 'bagon%';
+--------------------------------------+--------------------------+
| uuid | name |
+--------------------------------------+--------------------------+
| 92232041-9767-466b-a82f-20ecef0af6fa | bagon.fqdn |
+--------------------------------------+--------------------------+
1 row in set (0.00 sec)

The nova.compute_nodes table has 2 records for bagon, as expected : one is the old, deleted record and the other the current, live record.

The problem, as you can see above, is that the nova_api.resource_providers table had the old UUID for bagon. I'm not exactly sure at what point nova-compute on bagon started failing, I'm fairly confident it was OK after the reinstall, so I suspect something happened during the migration from pike to queens.

I manually updated the UUID in the resource_providers table, and bagon started working fine.

I can't try to repro because I can't downgrade the cluster to try the pike=>queens upgrade a second time, but hopefully you can.

Thanks !