Listing placement usages causes a circular reference error

[Chris Dent]

With the removal of oslo versioned objects from from the Usage and UsageList classes, serializing usages can result in a ValueError: Circular reference detected because there is a decimal.Decimal in the data to be returned.

This is a result of a func.sum used in the query to get lists of aggregates.

Note that the creation of a Decimal does not happen with sqlite, so the problem is not revealed by the functional gabbi tests. It happened to show up in the pending gabbi-based integration tests https://review.openstack.org/#/c/601614/ . See: http://logs.openstack.org/08/607508/14/check/placement-gabbi-tempest/f7c3eca/controller/logs/screen-placement-api.txt.gz#_Feb_25_22_37_31_423135 for an example.

This can be fixed by casting the 'used' value to an int when creating a Usage.

[Chris Dent (cdent)]

Fixed by: https://review.openstack.org/#/c/639216/

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/placement 1.0.0.0rc1 release candidate.