yahoo-eng-team team mailing list archive

[Alejandro Garcia <2078932@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

Hi all. It appears that there is no way, on newer API versions, of
"forcing" a destination host while performing a live migration.

We have seen this yesterday while trying to migrate some instances with
a scheduler hint for the JsonFilter. The hint was something like
"hypervisor_hostname in list of hosts". Obviously, we had some problems
with our hosts and needed to evacuate them, but the scheduler hint
prevented us from migrating the instances. We had to disable the
JsonFilter, perform the migration, and enable the filter again.

Checking at the docs for the API (https://docs.openstack.org/api-
ref/compute/#live-migrate-server-os-migratelive-action), it appears that
specifying a destination host for a migration does not bypass the
scheduler, for API microversion >= 2.30. Also, it seems that the force
option is available only until API microversion 2.67.

So, is there no way of overriding, removing or ignoring scheduler hints
during a migration? I understand completely bypassing scheduler filters
may be dangerous (specially when things like NUMA topology have to be
considered), but I also think it should be a supported use case to
"change our minds" about a hint, specially while migrating.

** Affects: nova
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2078932

Title:
  No way of removing scheduler hints while migrating on newer APIs?

Status in OpenStack Compute (nova):
  New

Bug description:
  Hi all. It appears that there is no way, on newer API versions, of
  "forcing" a destination host while performing a live migration.

  We have seen this yesterday while trying to migrate some instances
  with a scheduler hint for the JsonFilter. The hint was something like
  "hypervisor_hostname in list of hosts". Obviously, we had some
  problems with our hosts and needed to evacuate them, but the scheduler
  hint prevented us from migrating the instances. We had to disable the
  JsonFilter, perform the migration, and enable the filter again.

  Checking at the docs for the API (https://docs.openstack.org/api-
  ref/compute/#live-migrate-server-os-migratelive-action), it appears
  that specifying a destination host for a migration does not bypass the
  scheduler, for API microversion >= 2.30. Also, it seems that the force
  option is available only until API microversion 2.67.

  So, is there no way of overriding, removing or ignoring scheduler
  hints during a migration? I understand completely bypassing scheduler
  filters may be dangerous (specially when things like NUMA topology
  have to be considered), but I also think it should be a supported use
  case to "change our minds" about a hint, specially while migrating.

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