Instance existance not checked on evacuate

[Kravchenko Pavel]

In Change 42746 the check for instance existence been removed from instance evacuation flow.
It introduces a bug, because during evacuate to another host, similar to instance create, it must be checked that instance not yet exists on that host.

[melanie witt (melwitt)]

Link to the change that removed the check: https://review.openstack.org/#/c/42746

In the commit message, it says the "instance must exist in order to rebuild it," but the _check_instance_exists function actually checks the opposite -- it ensures the instance doesn't already exist on the target host.

[Guangya Liu (Jay Lau) (jay-lau-513)]

Will upload patch later. Thanks.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/44964

[Guangya Liu (Jay Lau) (jay-lau-513)]

Hi,

I have just appended a fix for this but was now marked as "Do not merge" and I want to get some comments from you.

In my understanding, when evacuate a VM instance to a target host, we need to make sure the VM instance does not exist on the target host, so my fix was rollback the patch of 42746 and make sure the VM instance does not exist on the target host. Any comments for the fix?

Since it is a critical issue, so hope I can get your comments soon so that I can make this done in havana.

Thanks.

[Kravchenko Pavel (kravchenko-pavel)]

Hi,

Your understanding is correct.
This check is definitely needed (like in case of manager._prebuild_instance).

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/45022

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/45029

[Guangya Liu (Jay Lau) (jay-lau-513)]

Hi, can anyone help review? I was trying to rollback the patch of 42746. Please show your comments if any, hope this will not be a blocking issue for havana release. Thanks.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/45029
Committed: http://github.com/openstack/nova/commit/3a48920193cb8ce370453dbcdea6be7a1806f0f5
Submitter: Jenkins
Branch: master

commit 3a48920193cb8ce370453dbcdea6be7a1806f0f5
Author: Jay Lau <email address hidden>
Date: Wed Sep 4 18:11:03 2013 +0800

    Check instance exists or not when evacuate

    When evacuate instance to another host, similar to instance create,
    nova compute must make sure the instance not yet exist on the host.

    Currently there is no check for this, the fix was add the checking
    of instance exist or not when evacuate.

    Fix bug 1216501

    Change-Id: I3ccbd5db5174904e17ffa8f9236ca4e1a09f4dbe