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[Matt Riedemann <mriedem.os@xxxxxxxxx>]

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

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

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

** Changed in: nova/newton
       Status: New => Confirmed

** Changed in: nova/ocata
       Status: New => Confirmed

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

** Changed in: nova/newton
   Importance: Undecided => Medium

** Changed in: nova/ocata
   Importance: Undecided => Medium

** Changed in: nova/pike
   Importance: Undecided => Medium

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https://bugs.launchpad.net/bugs/1718512

Title:
  migration fails if instance build failed on destination host

Status in OpenStack Compute (nova):
  In Progress
Status in OpenStack Compute (nova) newton series:
  Confirmed
Status in OpenStack Compute (nova) ocata series:
  Confirmed
Status in OpenStack Compute (nova) pike series:
  Confirmed

Bug description:
  (OpenStack Nova, commit d8b30c3772, per OSA-14.2.7)

  if an instance build fails on a hypervisor the "retry" field of the
  instance's request spec is populated with which host and how many
  times it attempted to retry the build. this field remains populated
  during the life-time of the instance.

  if a live-migration for the same instance is requested, the conductor
  loads this request spec and passes it on to the scheduler. the
  scheduler will fail the migration request on RetryFilter since the
  target was already known to have failed (albeit, for the build).

  with the help of mriedem and melwitt of #openstack-nova, we determined
  that migration retries are handled separately from build retries.
  mriedem suggested a patch to ignore the retry field of the instance
  request spec during migrations. this patch allowed the failing
  migration to succeed.

  it is important to note that it may fail the migration again, however
  there is still sufficient reason to ignore the build's
  failures/retries during a migration.

  12:55 < mriedem> it does stand to reason that if this instance failed to build originally on those 2 hosts, that live migrating it there might fail too...but we don't know why it originally failed, could have been a resource claim issue at the time
  12:58 < melwitt> yeah, often it's a failed claim. and also what if that compute host is eventually replaced over the lifetime of the cluster, making it a fresh candidate for several instances that might still avoid it because they once failed to build there back when it was a different machine

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