Hard deleting instance does not take into account soft-deleted referential constraints

[Matt Riedemann]

The instance hard delete code is new in Train but has a bug noted here:

https://review.opendev.org/#/c/570202/8/nova/db/sqlalchemy/api.py@1804

The hard delete of the instance can fail if there are related soft-deleted records (like detached volumes [bdms]), because I hit this in a gate run of the cross-cell resize stuff:

http://paste.openstack.org/show/752057/

'Cannot delete or update a parent row: a foreign key constraint fails (`nova_cell2`.`block_device_mapping`, CONSTRAINT `block_device_mapping_instance_uuid_fkey` FOREIGN KEY (`instance_uuid`) REFERENCES `instances` (`uuid`))') [SQL: 'DELETE FROM instances WHERE instances.uuid = %(uuid_1)s'] [parameters: {'uuid_1': '4b8a12c4-e28a-49cc-a681-236c1e8a174c'}]

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/661398

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/661398
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=0b92c7e741b5abb1df70cc1d3bb8f0d1989cf2f5
Submitter: Zuul
Branch: master

commit 0b92c7e741b5abb1df70cc1d3bb8f0d1989cf2f5
Author: Matt Riedemann <email address hidden>
Date: Fri May 24 17:08:20 2019 -0400

    Fix hard-delete of instance with soft-deleted referential constraints

    When hard-deleting an instance we first delete related records
    but the code was not taking into account soft-deleted related
    records which will result in the instance delete failing due to
    a referential constraint because soft-deleted records are not
    really deleted when it comes to table constraints.

    This fixes the issue by simply passing read_deleted='yes' to the
    related record model query in the hard delete path.

    The related unit test is updated to cover this scenario and a
    typo in that same test is also fixed here.

    Change-Id: I9fc5a9cc40ceffc450c1fde1df7fb36581e9cc94
    Closes-Bug: #1830438

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 20.0.0.0rc1 release candidate.