Flavor Extra Spec and Image Properties Validation

https://blueprints.launchpad.net/nova/+spec/flavor-extra-spec-image-property-validation

Problem description

Currently flavor extra-specs and image properties validation are done in separate places. If they are not compatible, the instance may fail to launch and go into an ERROR state, or may reschedule an unknown number of times depending on the virt driver behaviour.

Use Cases

As an end user I would like to have instant feedback if flavor extra spec or image properties are not valid or they are not compatible with each other so I can correct my configuration and retry the operation.

Proposed change

We want to validate the combination of the flavor extra-specs and image properties as early as possible once they’re both known.

If validation fails then synchronously return error to user.

We’d need to do this anywhere the flavor or image changes, so basically instance creation, rebuild, and resize. More precisely, rename _check_requested_image() to something more generic, take it out of _checks_for_create_and_rebuild(), modify it to check more things and call it from all three operations: creation, rebuild, and resize.

Note

Only things that are not virt driver specific are validated.

Examples of validations to be added 1:

  • Call hardware.numa_get_constraints to validate all the various numa-related things. This is currently done only on _create_instance(), should be done for resize/rebuild as well.

  • Ensure that the cpu policy, cpu thread policy and emulator thread policy values are valid.

  • Validate the realtime mask.

  • Validate the number of serial ports.

  • Validate the cpu topology constraints.

  • Validate the quota:* settings (that are not virt driver specific) in the flavor.

Alternatives

None

Data model impact

None

REST API impact

Due to the new validations, users could face more 4xx errors for more cases than we did before in create/rebuild/resize operations.

Security impact

None

Notifications impact

None

Other end user impact

None

Performance Impact

Negligible.

Other deployer impact

None

Developer impact

None

Upgrade impact

None

Implementation

Assignee(s)

Primary assignee:

jackding

Work Items

  • Add validations mostly in nova/compute/api.py.

  • Add/update unit tests.

  • Update documentation/release-note if necessary depending on the new validations added.

Dependencies

None

Testing

Will add unit tests.

Documentation Impact

None

History

Revisions

Release Name

Description

Stein

Introduced