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[Matt Riedemann <mriedem.os@xxxxxxxxx>]

** Tags added: placement resize

** Summary changed:

- Allocations not deleted on failed resize
+ Allocations not deleted on failed resize_instance

** Changed in: nova
   Importance: Undecided => Medium

** Also affects: nova/pike
   Importance: Undecided
       Status: New

** Also affects: nova/ocata
   Importance: Undecided
       Status: New

** Also affects: nova/queens
   Importance: Undecided
       Status: New

** Changed in: nova/ocata
       Status: New => Confirmed

** Changed in: nova/pike
       Status: New => Confirmed

** Changed in: nova/queens
       Status: New => Confirmed

** Changed in: nova/pike
   Importance: Undecided => Medium

** Changed in: nova/queens
   Importance: Undecided => Medium

** Changed in: nova/ocata
   Importance: Undecided => Medium

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https://bugs.launchpad.net/bugs/1749215

Title:
  Allocations not deleted on failed resize_instance

Status in OpenStack Compute (nova):
  In Progress
Status in OpenStack Compute (nova) ocata series:
  Confirmed
Status in OpenStack Compute (nova) pike series:
  Confirmed
Status in OpenStack Compute (nova) queens series:
  Confirmed

Bug description:
  Description
  ===========

  During a resize, an instance's allocations are removed and replaced by
  2 sets of allocations instead. If a resize is completed sucessfully,
  one set of allocations is correctly removed, but in case of a failure,
  neither set of allocations is removed. Only one set of allocations are
  removed if the instance is deleted.

  This happens because the call self.compute_rpcapi.resize_instance [1]
  is an RPC cast (async), instead of a call (sync). Because of this, the
  Except branch [2] in which the allocation is cleared and the instance
  is rescheduled, is never called.

  Additionally, because not all of the allocations are cleared, the
  resources on the compute nodes will become "locked" and unusable. At
  some point, instances will no longer be scheduled to those compute
  nodes, due to all the resources being "allocated".

  [1] https://github.com/openstack/nova/blob/master/nova/compute/manager.py#L4085
  [2] https://github.com/openstack/nova/blob/master/nova/compute/manager.py#L4123

  
  Steps to reproduce
  ==================

  * Spawn an instance.
  * Observe that the table nova_api.allocations only has 1 set of allocations for the instance (VCPU, MEMORY, DISK).
  * Cold resize to an invalid flavor (e.g.: smaller disk).
  * Observe that the table nova_api.allocations has 2 sets of allocations for the instance.
  * Observe that the cold resize failed, and that the instance's task state has been reverted to its original state.
  * Observe that the table nova_api.allocations continues to have 2 sets of allocations.
  * Delete the instance.
  * Observe even after the instance has been destroyed, there is still 1 set of allocations for the instance.

  
  Expected result
  ===============

  After the cold resize failed, there should be only 1 set of
  allocations in the nova_api.allocations table, and after deleting the
  instance, there shouldn't be any.

  
  Actual result
  =============

  After the cold resize failed, there are 2 sets of allocations in the
  nova_api.allocations table, after deleting the instance, there is 1
  set of allocations.

  
  Environment
  ===========

  Branch: Queens
  Hypervisor: Hyper-V Server 2012 R2 (unrelated)

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