yahoo-eng-team team mailing list archive

[Matt Riedemann <mriedem.os@xxxxxxxxx>]

Public bug reported:

When we resize a server, we update the RequestSpec.flavor because for
later move operations of the server, the RequestSpec is what gets passed
to the scheduler, so naturally we need the RequestSpec.flavor to match
the instance.flavor after the instance is resized. That happens here:

https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/conductor/manager.py#L313

https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/conductor/manager.py#L352

However, if the resize is reverted, we don't actually rollback the
RequestSpec.flavor to the previously flavor (instance.old_flavor):

https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/compute/api.py#L3322

So consider this scenario:

1. create server with flavor 1
2. resize to server 2 (VERIFY_RESIZE status); at this point the RequestSpec.flavor is 2
3. revert the resize
4. live migrate, shelve/unshelve, evacuate or cold migrate the server - the request spec passed to the scheduler will have flavor 2 rather than flavor 1 which could cause misleading scheduling failures, e.g. if flavor 2 is bigger than flavor 1 and there is no capacity for flavor 2 on any hosts, the scheduler would raise NoValidHost.

** Affects: nova
     Importance: Medium
         Status: Triaged

** Affects: nova/ocata
     Importance: Undecided
         Status: New

** Affects: nova/pike
     Importance: Undecided
         Status: New

** Affects: nova/queens
     Importance: Undecided
         Status: New


** Tags: request-spec resize

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https://bugs.launchpad.net/bugs/1785339

Title:
  RequestSpec.flavor is not reverted on resize revert

Status in OpenStack Compute (nova):
  Triaged
Status in OpenStack Compute (nova) ocata series:
  New
Status in OpenStack Compute (nova) pike series:
  New
Status in OpenStack Compute (nova) queens series:
  New

Bug description:
  When we resize a server, we update the RequestSpec.flavor because for
  later move operations of the server, the RequestSpec is what gets
  passed to the scheduler, so naturally we need the RequestSpec.flavor
  to match the instance.flavor after the instance is resized. That
  happens here:

  https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/conductor/manager.py#L313

  https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/conductor/manager.py#L352

  However, if the resize is reverted, we don't actually rollback the
  RequestSpec.flavor to the previously flavor (instance.old_flavor):

  https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/compute/api.py#L3322

  So consider this scenario:

  1. create server with flavor 1
  2. resize to server 2 (VERIFY_RESIZE status); at this point the RequestSpec.flavor is 2
  3. revert the resize
  4. live migrate, shelve/unshelve, evacuate or cold migrate the server - the request spec passed to the scheduler will have flavor 2 rather than flavor 1 which could cause misleading scheduling failures, e.g. if flavor 2 is bigger than flavor 1 and there is no capacity for flavor 2 on any hosts, the scheduler would raise NoValidHost.

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