Failure in resize_instance after cast to finish_resize still sets instance error state

[Matthew Booth]

This is from code inspection only.

ComputeManager.resize_instance does:

  with self._error_out_instance_on_exception(context, instance,
                                             quotas=quotas):
      ...stuff...

      self.compute_rpcapi.finish_resize(context, instance,
                    migration, image, disk_info,
                    migration.dest_compute, reservations=quotas.reservations)

      ... Responsibility for the instance has now been punted to the destination, but...

      self._notify_about_instance_usage(context, instance, "resize.end",
                                              network_info=network_info)

      compute_utils.notify_about_instance_action(context, instance,
                   self.host, action=fields.NotificationAction.RESIZE,
                   phase=fields.NotificationPhase.END)
      self.instance_events.clear_events_for_instance(instance)

The problem is that a failure in anything after the cast to finish_resize will cause the instance to be put in an error state and its quotas rolled back. This would not be correct, as any error here would be purely ephemeral. The resize operation will continue on the destination regardless, so this would almost certainly result in an inconsistent state.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/462499

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matthew Booth (<email address hidden>) on branch: master
Review: https://review.openstack.org/462499
Reason: This came loose from my series fixing this.

[Matt Riedemann (mriedem)]

Putting back to New to re-triage this.

[Matt Riedemann (mriedem)]

This is true, and I left comments in the patch (it would still need work). It's also true of a *ton* of post-processing type code all over the compute manager where things in post ops could still fail on unnecessary stuff and result in errors even though the guest might be OK.