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Reviewed:  https://review.openstack.org/543971
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=caf167862dd82e98f0189c9598856de57dfa7d35
Submitter: Zuul
Branch:    master

commit caf167862dd82e98f0189c9598856de57dfa7d35
Author: Claudiu Belu <cbelu@xxxxxxxxxxxxxxxxxxxxxx>
Date:   Sun Feb 11 10:07:52 2018 -0800

    compute: Cleans up allocations after failed resize
    
    During cold resize, the ComputeManager's prep_resize calls the
    rpcapi.ComputeAPI's resize_instance method, which will then do an
    RPC cast (async).
    
    Because the RPC cast is asynchronous, the exception branch in prep_resize
    will not be executed if the cold resize failed, the allocations will not
    be cleaned up, and the instance will not be rescheduled.
    
    This patch adds allocation cleanup in the resize_instance and finish_resize
    methods.
    
    Change-Id: I2d9ab06b485f76550dbbff46f79f40ff4c97d12f
    Closes-Bug: #1749215


** Changed in: nova
       Status: In Progress => Fix Released

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

Title:
  Allocations not deleted on failed resize_instance

Status in OpenStack Compute (nova):
  Fix Released
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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