Support for tracking traits removed from provider.yaml

https://blueprints.launchpad.net/nova/+spec/copy-applied-provider-yaml

This specification proposes a feature to ensure that traits removed from the provider.yaml are also properly deleted from the resource provider.

Problem description

Nova-compute has a feature to register custom traits with the resource provider using config files (provider.yaml). https://docs.openstack.org/nova/latest/admin/managing-resource-providers.html

In this configuration file, even if the values of custom traits are modified or the trait is deleted, the original trait does not be removed from the target resource provider. In scenarios where the custom trait registered with the resource provider is replaced and old custom traits affect scheduling, this behavior can be a problem.

Use Cases

• As a cloud operator, I would like to ensure that only one trait is registered with the resource provider for custom traits of the same type.

• As a cloud operator, I would like to complete the registration of custom traits in the config file of nova-compute without additional implementation (calling the Placement API using API/CLI in another system).

Proposed change

We propose adding a process for nova-compute to copy the contents of the provider.yaml file to /var/lib/nova/applied_provider.yaml after they have been applied to the placement.

Then, when updating the placement based on the provider.yaml file, nova-compute perform a diff between /var/lib/nova/applied_provider.yaml and /etc/nova/provider.yaml to detect if any traits have been removed from the provider.yaml file.

For now, the diff is limited to traits, but later this logic can be extended to allow the use of the diff for any part of the provider.yaml.

Alternatives

• Register only the custom traits defined in the file with the resource provider, treating provider.yaml as declarative data. However, this is a destructive change and there are concerns about the impact on the existing environment.

• Add a definition like declarative_prefix to provider.yaml to handle only traits with a declarative_prefix declaratively. In this case, the extensibility to non-trait elements in provider.yaml is limited, and both the definition in provider.yaml and the code of the resource tracker become complex.

Data model impact

None

REST API impact

None

Security impact

None

Notifications impact

None

Other end user impact

None

Performance Impact

No performance impact on nova is anticipated. If there are frequent updates to custom traits, requests for deleting and creating traits will be frequently sent to the Placement API.

Other deployer impact

None

Developer impact

None

Upgrade impact

None

Implementation

Assignee(s)

Primary assignee:

mkuroha

Other contributors:

None

Feature Liaison

Feature liaison:

Liaison Needed

Work Items

• Implement the copying of provider.yaml and extraction of trait diffs with applied_provider.yaml in the _merge_provider_configs method.

Dependencies

None

Testing

• Add unit/functional tests

Documentation Impact

Update the existing Managing Resource Providers Using Config Files guide to explation the behavior with applied_provider.yaml.

References

None

History

Revisions

Release Name	Description
2025.2 Flamingo	Introduced