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[Matt Riedemann <mriedem.os@xxxxxxxxx>]

Public bug reported:

This is a follow on to bug 1712411 where pre_live_migration fails on the
destination host here:

https://github.com/openstack/nova/blob/0e52b3fe686ce1fc43fd3790711731bc806c6ad0/nova/compute/manager.py#L5456

And the source node starts rolling back things like volume connections
on the destination host:

https://github.com/openstack/nova/blob/0e52b3fe686ce1fc43fd3790711731bc806c6ad0/nova/compute/manager.py#L5836

The tricky thing is we maybe can't cleanup the allocations from the
_rollback_live_migration method since that's also passed to the virt
driver in case live migration fails in the driver:

https://github.com/openstack/nova/blob/0e52b3fe686ce1fc43fd3790711731bc806c6ad0/nova/compute/manager.py#L5467

We might be unsure of what is actually running on the destination node
and consuming resources at that point, however, the instance.host and
instance.node should be pointed to the source node at that point of
failure anyway, so removing the allocations on the destination node from
within _rollback_live_migration should be OK, but it might require some
investigation.

** Affects: nova
     Importance: High
         Status: Triaged

** Affects: nova/pike
     Importance: Undecided
         Status: Triaged


** Tags: live-migration placement

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

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

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https://bugs.launchpad.net/bugs/1715182

Title:
  _rollback_live_migration does not remove allocations from destination
  node

Status in OpenStack Compute (nova):
  Triaged
Status in OpenStack Compute (nova) pike series:
  Triaged

Bug description:
  This is a follow on to bug 1712411 where pre_live_migration fails on
  the destination host here:

  https://github.com/openstack/nova/blob/0e52b3fe686ce1fc43fd3790711731bc806c6ad0/nova/compute/manager.py#L5456

  And the source node starts rolling back things like volume connections
  on the destination host:

  https://github.com/openstack/nova/blob/0e52b3fe686ce1fc43fd3790711731bc806c6ad0/nova/compute/manager.py#L5836

  The tricky thing is we maybe can't cleanup the allocations from the
  _rollback_live_migration method since that's also passed to the virt
  driver in case live migration fails in the driver:

  https://github.com/openstack/nova/blob/0e52b3fe686ce1fc43fd3790711731bc806c6ad0/nova/compute/manager.py#L5467

  We might be unsure of what is actually running on the destination node
  and consuming resources at that point, however, the instance.host and
  instance.node should be pointed to the source node at that point of
  failure anyway, so removing the allocations on the destination node
  from within _rollback_live_migration should be OK, but it might
  require some investigation.

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