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[Thierry Carrez <thierry.carrez+lp@xxxxxxxxx>]

** Changed in: nova
       Status: Fix Committed => Fix Released

** Changed in: nova
    Milestone: None => liberty-3

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https://bugs.launchpad.net/bugs/1429220

Title:
  libvirt does ensure live migration will eventually complete (or abort)

Status in OpenStack Compute (nova):
  Fix Released

Bug description:
  Currently the libvirt driver's approach to live migration is bested
  characterized as "launch & pray".  It starts the live migration
  operation and then just unconditionally waits for it to finish. It
  never makes any attempt to tune its behaviour (for example changing
  max downtime), nor does it look at the data transfer statistics to
  check if it is making any progress, nor does it have any overall
  timeout.

  It is not uncommon for guests to have workloads that will preclude
  live migration from completing. Basically they can be dirtying guest
  RAM (or block devices) faster than the network is able to transfer it
  to the destination host. In such a case Nova will just leave the
  migration running, burning up host CPU cycles and trashing network
  bandwidth until the end of the universe.

  There are many features exposed by libvirt, that Nova could be using
  to do a better job, but the question is obviously ...which features
  and how should they be used. Fortunately Nova is not the first project
  to come across this problem. The oVirt data center mgmt project has
  the exact same problem. So rather than trying to invent some new logic
  for Nova, we should, as an immediate bug fix task, just copy the oVirt
  logic from VDSM

  https://github.com/oVirt/vdsm/blob/master/vdsm/virt/migration.py#L430

  If we get this out to users and then get real world feedback on how it
  operates, we will have an idea of how/where to focus future ongoing
  efforts.

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