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[Matt Riedemann <mriedem.os@xxxxxxxxx>]

Public bug reported:

This is based on code inspection and related to bug 1815153 (see
comments 1-4) but when we rebuild a server with a new image we go
through the scheduler with a special scheduler hint:

https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/compute/api.py#L3336

This line is meant to avoid accidentally persisting that change:

https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/compute/api.py#L3329

But RequestSpec.save() doesn't use the id field, it looks up the
RequestSpec from the DB using the instance_uuid field to save the
changes:

https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/objects/request_spec.py#L619

Which means we could accidentally persist that scheduler hint here if we
are 'healing' a  volume-backed server (since Rocky):

https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/conductor/manager.py#L1009

The potential fallout from this is that future move operations of that
server could only run a subset of the scheduler filters:

https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/scheduler/manager.py#L125

And not even call placement...

** Affects: nova
     Importance: Undecided
         Status: New

** Affects: nova/rocky
     Importance: Undecided
         Status: New

** Affects: nova/stein
     Importance: Undecided
         Status: New


** Tags: rebuild request-spec

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https://bugs.launchpad.net/bugs/1823369

Title:
  _nova_check_type scheduler hint could be accidentally persisted during
  a rebuild with image change

Status in OpenStack Compute (nova):
  New
Status in OpenStack Compute (nova) rocky series:
  New
Status in OpenStack Compute (nova) stein series:
  New

Bug description:
  This is based on code inspection and related to bug 1815153 (see
  comments 1-4) but when we rebuild a server with a new image we go
  through the scheduler with a special scheduler hint:

  https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/compute/api.py#L3336

  This line is meant to avoid accidentally persisting that change:

  https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/compute/api.py#L3329

  But RequestSpec.save() doesn't use the id field, it looks up the
  RequestSpec from the DB using the instance_uuid field to save the
  changes:

  https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/objects/request_spec.py#L619

  Which means we could accidentally persist that scheduler hint here if
  we are 'healing' a  volume-backed server (since Rocky):

  https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/conductor/manager.py#L1009

  The potential fallout from this is that future move operations of that
  server could only run a subset of the scheduler filters:

  https://github.com/openstack/nova/blob/a6963fa6858289d048e4d27ce8e61637cd023f4c/nova/scheduler/manager.py#L125

  And not even call placement...

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