Cannot live block migrate an instance without shared storage

[Rohit Karajgi]

In the current trunk (Havana): commit d8c9864d95bec6d2babb2cb5a2aeeb284fca4834,

Live migration without shared storage (block migration) is failing.

Problem:
A check in pre_live_migration at the destination for the instance existence fails and the respective instance directory gets created.
https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L3367

The same check is performed on the destination during pre_block_migration, the instance directory is found and an exception
is raised, and migration fails :
https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L3422

[Chet Burgess (cfb-n)]

I can confirm this too. We hit this a few days ago. I have a fix for this already I've been meaning to submit.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/34661

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/34661
Committed: http://github.com/openstack/nova/commit/659ec75eaf052742a6269e0aae258f1c874749f7
Submitter: Jenkins
Branch: master

commit 659ec75eaf052742a6269e0aae258f1c874749f7
Author: Chet Burgess <email address hidden>
Date: Wed Jul 3 17:00:37 2013 +0000

    Check instance on dest once during block migration

    During live block migrations both pre_live_migration and
    pre_block_migration check for the presence of the instance on
    the destination and create the instance dir if it doesn't exist.

    As a result the call to pre_block_migration always fails as
    pre_live_migration has already created the instance dir on the
    destination.

    As it turns out the pre_block_migration call is completely
    unnecessary. The libvirt driver is the only driver that uses the
    call and the work it does can easily be done in the existing
    pre_live_migration call. In order to streamline things we
    completely remove the pre_block_migration call from all
    drivers. Additionally we update the function definition for
    pre_live_migration to pass needed disk info down to the
    virt drivers.

    Fixes bug: #1193359
    Change-Id: Id9dfe482db3471d6a1b9b6c7d59a5ddc48775d7f

[Xavier Queralt (xqueralt-deactivatedaccount)]

This bug also affects grizzly

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/grizzly
Review: https://review.openstack.org/42588

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/42588
Committed: http://github.com/openstack/nova/commit/53a57e0aaac23798a6f1b1619f4c767e1621850e
Submitter: Jenkins
Branch: stable/grizzly

commit 53a57e0aaac23798a6f1b1619f4c767e1621850e
Author: Chet Burgess <email address hidden>
Date: Wed Jul 3 17:00:37 2013 +0000

    Check instance on dest once during block migration

    During live block migrations both pre_live_migration and
    pre_block_migration check for the presence of the instance on
    the destination and create the instance dir if it doesn't exist.

    As a result the call to pre_block_migration always fails as
    pre_live_migration has already created the instance dir on the
    destination.

    As it turns out the pre_block_migration call is completely
    unnecessary. The libvirt driver is the only driver that uses the
    call and the work it does can easily be done in the existing
    pre_live_migration call. In order to streamline things we
    completely remove the pre_block_migration call from all
    drivers. Additionally we update the function definition for
    pre_live_migration to pass needed disk info down to the
    virt drivers.

    Fixes bug: #1193359

    (cherry picked from commit 659ec75eaf052742a6269e0aae258f1c874749f7)

    Conflicts:
     nova/compute/manager.py
     nova/tests/test_libvirt.py
     nova/virt/libvirt/driver.py
     nova/virt/xenapi/driver.py

    Change-Id: Id9dfe482db3471d6a1b9b6c7d59a5ddc48775d7f