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[OpenStack Infra <1797580@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.openstack.org/610098
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=ce3af5e33ae6843411e611e81c6ca1c21e0f1e09
Submitter: Zuul
Branch:    master

commit ce3af5e33ae6843411e611e81c6ca1c21e0f1e09
Author: Matt Riedemann <mriedem.os@xxxxxxxxx>
Date:   Fri Oct 12 12:03:41 2018 -0400

    Don't persist RequestSpec.requested_destination
    
    The RequestSpec.requested_destination, similar to the
    retry field, is per-request/operation, and persisting
    it can caues issues when subsequent move requests.
    
    For example, if you cold migrate a server to a specific
    host and then live migrate that server without specifying
    a host, the requested target host from the cold migrate
    is sent to the scheduler for the live migration, but since
    that is where the instance is already running, it's
    rejected with NoValidHost.
    
    This is a similar issue to the need to call
    RequestSpec.reset_forced_destinations() in all move operations
    in conductor. However, rather than try to whack this mole in
    every place the request spec is sent to the scheduler, like
    reset_forced_destinations() is used, we simply don't need to
    persist the requested_destination field since it's just a
    vehicle to tell the scheduler which host we want.
    
    The related functional regression test is updated to show
    the bug is now fixed.
    
    Change-Id: I2a78f0754c63381c57e7e1c610d0938b6df0f537
    Closes-Bug: #1797580


** Changed in: nova
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1797580

Title:
  NoValidHost during live migration after cold migrating to a specified
  host

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

Bug description:
  I recreated this with a 2-node devstack in stein created yesterday.

  1. create a server
  2. cold migrate the server to the other host and specify the host: nova migrate <server> --host <other host>
  3. confirm the resize
  4. live migrate the server w/o specifying a host so the scheduler has to pick one

  At this point, you get a NoValidHost error because the scheduler is
  restricted to the current host on which the instance is running
  because of the requested_destination field that is persisted in the
  request spec from step 2:

  http://paste.openstack.org/show/731972/

  The problem is when cold migrating a server with a specified target
  host, compute API stores that on the request spec and sends it to the
  conductor to tell the scheduler which host to use:

  https://github.com/openstack/nova/blob/20bc0136d0665bafdcd379f19389a0a5ea7bf310/nova/compute/api.py#L3565

  But that request spec requested_destination field gets persisted and
  then when you live migrate, it's re-used but since the server is
  already on that host, we get NoValidHost since you can't live migrate
  to the same host.

  This is a regression in Queens:
  https://review.openstack.org/#/c/408955/

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