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[Matt Riedemann <mriedem@xxxxxxxxxx>]

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

** Changed in: nova/liberty
       Status: New => In Progress

** Changed in: nova/liberty
     Assignee: (unassigned) => jichenjc (jichenjc)

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https://bugs.launchpad.net/bugs/1510979

Title:
  Instance reschedule failure leaves orphaned neutron ports

Status in OpenStack Compute (nova):
  Fix Released
Status in OpenStack Compute (nova) liberty series:
  In Progress

Bug description:
  During the instance boot (spawn/run) process, neutron ports are
  allocated for the instance if necessary. If the instance fails to
  spawn (say as a result of a compute host failure), the default
  behavior is to reschedule the instance and leave it's networking
  resources in-tact for potential reuse on the rescheduled host (as per
  deallocate_networks_on_reschedule() [1] which returns False for most
  compute drivers).

  All is good if the instance is successfully rescheduled, but if the
  reschedule fails (say no more applicable hosts) the allocated ports
  are left as-is and effectively orphaned.

  There are some related defects ([2] and [3]), but they don't quite
  touch on the particular behavior described herein.

  Obviously there are a number of ways to address this issue, but the
  most obvious is perhaps nova should be aware of the reschedule failure
  and deallocate any resources which may have been left in-tact for the
  reschedule.

  I'm running devstack all-in-one setup from openstack master branches.

  nova --version
  2.32.0
  neutron --version
  3.1.0

  The easiest way to repo is to use an all-in-one devstack (only 1
  compute host) simulate a host spawn failure by editing the spwan()
  method of your compute driver to raise an exception at the end of the
  method and simply try to boot a server. In this setup there's only 1
  host so the reschedule will fail and you can verify the port allocated
  for the instance still exists after trying to boot the instance.

  
  [1] https://github.com/openstack/nova/blob/master/nova/virt/driver.py#L1273
  [2] https://bugs.launchpad.net/nova/+bug/1410739
  [3] https://bugs.launchpad.net/nova/+bug/1327124

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