resource update conflict

[dzogchen]

when performing several operations that change the generation of a resource (node), a ResourceProviderUpdateConflict error occurs.

the error appeared when the following operations were performed sequentially in a separate script: creating an aggregate, adding a host to the aggregate, adding a compute node (status disabled -> enabled), evacuating instances to the added node (one of the evacuated instances went into an error state)

nova.exception.ResourceProviderUpdateConflict: A conflict was encountered attempting to update resource provider 7738e7a2-e64f-4830-a482-5a93951b5e6e (generation 9): {"errors": [{"status": 409, "title": "Conflict", "detail": "There was a conflict when trying to complete your request.\\n\\n Resource provider\'s generation already changed. Please update the generation and try again. ", "request_id": "req-899e1d4f-9158-4729-b70b-814805bba247"}]}\n'}

solution:
https://opendev.org/openstack/nova/src/branch/master/nova/compute/resource_tracker.py#L1195 (add a wait parameter to the decorator before the next attempt - wait_fixed=2000)

https://review.opendev.org/c/openstack/nova/+/888452/1