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[Rodrigo Barbieri <rodrigo.barbieri@xxxxxxxxxxxxx>]

Public bug reported:


Description:

When performing a cold migration, if an exception is raised by the
driver during confirm_migration (this runs in the source node), the
migration record is stuck in "confirming" state and the allocations
against the source node are not removed.

The instance is fine at the destination in this stage, but the source
host has allocations that is not possible to clean without going to the
database or invoking the Placement API via curl. After several migration
attempts that fail in the same spot, the source node is filled with
these allocations that prevent new instances from being created or
instances migrated to this node.

When confirm_migration fails in this stage, the migrating instance can
be saved through a hard reboot or a reset state to active.

Steps to reproduce:

Unfortunately, I don't have logs of the real root cause of the problem
inside driver.confirm_migration running libvirt driver. However, the
stale allocations and migration status problem can be easily reproduced
by raising an exception in libvirt driver's confirm_migration method,
and it would affect any driver.

Expected results:

Discussed this issue with efried and mriedem over #openstack-nova on
March 25th, 2019. They confirmed that allocations not being cleared up
is a bug.

Actual results:

Instance is fine at the destination after a reset-state. Source node has
stale allocations that prevent new instances from being created/migrated
to the source node. Migration record is stuck in "confirming" state.

Environment:

I verified this bug on on pike, queens and stein branches. Running
libvirt KVM driver.

** Affects: nova
     Importance: Medium
         Status: Triaged


** Tags: compute placement resize

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https://bugs.launchpad.net/bugs/1821594

Title:
  Error in confirm_migration leaves stale allocations and 'confirming'
  migration state

Status in OpenStack Compute (nova):
  Triaged

Bug description:
  
  Description:

  When performing a cold migration, if an exception is raised by the
  driver during confirm_migration (this runs in the source node), the
  migration record is stuck in "confirming" state and the allocations
  against the source node are not removed.

  The instance is fine at the destination in this stage, but the source
  host has allocations that is not possible to clean without going to
  the database or invoking the Placement API via curl. After several
  migration attempts that fail in the same spot, the source node is
  filled with these allocations that prevent new instances from being
  created or instances migrated to this node.

  When confirm_migration fails in this stage, the migrating instance can
  be saved through a hard reboot or a reset state to active.

  Steps to reproduce:

  Unfortunately, I don't have logs of the real root cause of the problem
  inside driver.confirm_migration running libvirt driver. However, the
  stale allocations and migration status problem can be easily
  reproduced by raising an exception in libvirt driver's
  confirm_migration method, and it would affect any driver.

  Expected results:

  Discussed this issue with efried and mriedem over #openstack-nova on
  March 25th, 2019. They confirmed that allocations not being cleared up
  is a bug.

  Actual results:

  Instance is fine at the destination after a reset-state. Source node
  has stale allocations that prevent new instances from being
  created/migrated to the source node. Migration record is stuck in
  "confirming" state.

  Environment:

  I verified this bug on on pike, queens and stein branches. Running
  libvirt KVM driver.

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