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[OpenStack Infra <1785339@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.openstack.org/588689
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=ef3849e2da1c94df519debcb14ba15af9bd01a60
Submitter: Zuul
Branch:    master

commit ef3849e2da1c94df519debcb14ba15af9bd01a60
Author: Matt Riedemann <mriedem.os@xxxxxxxxx>
Date:   Fri Aug 3 19:11:37 2018 -0400

    Update RequestSpec.flavor on resize_revert
    
    Since I8abdf58a6537dd5e15a012ea37a7b48abd726579 in Newton
    we update the RequestSpec.flavor to the new flavor during
    a resize. However, if the resize is reverted, we didn't
    revert the RequestSpec.flavor to the previous flavor
    on the instance, which could cause issues later when
    moving the instance since the scheduler will get a
    RequestSpec with a flavor that doesn't match the actual
    flavor on the instance.
    
    This fixes the bug by updating the RequestSpec.flavor
    with instance.old_flavor on resize_revert in the API.
    Functional test wrinkles are added.
    
    This fix was ported from the starlingx-staging/stx-nova
    repo commit 71acfeae0.
    
    Change-Id: Ic6e74702f2a5b57b437f4ffdfbc86c1e34cdac7d
    Closes-Bug: #1785339


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

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https://bugs.launchpad.net/bugs/1785339

Title:
  RequestSpec.flavor is not reverted on resize revert

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:
  When we resize a server, we update the RequestSpec.flavor because for
  later move operations of the server, the RequestSpec is what gets
  passed to the scheduler, so naturally we need the RequestSpec.flavor
  to match the instance.flavor after the instance is resized. That
  happens here:

  https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/conductor/manager.py#L313

  https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/conductor/manager.py#L352

  However, if the resize is reverted, we don't actually rollback the
  RequestSpec.flavor to the previously flavor (instance.old_flavor):

  https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/compute/api.py#L3322

  So consider this scenario:

  1. create server with flavor 1
  2. resize to server 2 (VERIFY_RESIZE status); at this point the RequestSpec.flavor is 2
  3. revert the resize
  4. live migrate, shelve/unshelve, evacuate or cold migrate the server - the request spec passed to the scheduler will have flavor 2 rather than flavor 1 which could cause misleading scheduling failures, e.g. if flavor 2 is bigger than flavor 1 and there is no capacity for flavor 2 on any hosts, the scheduler would raise NoValidHost.

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