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Isn’t just handling the exception instance_not_found enough? By this time source would’ve been cleaned up. Destination VM resources will get cleaned up by the periodic task since the VM is not associated with this host. Am I missing something here?


From: 王宏 [mailto:w.wanghong1 at gmail.com]
Sent: 16 December 2013 11:32
To: openstack-dev at lists.openstack.org
Subject: [openstack-dev] [Nova][libvirt]when deleting instance which is in migrating state, instance files can be stay in destination node forever

Hi all.
When I try to fix a bug:https://bugs.launchpad.net/nova/+bug/1242961,
I get a trouble.

To reproduce the bug is very easy. Live migrate a vm in block_migration mode,
and then delelte the vm immediately.

The reason of this bug is as follow:
1. Because live migrate costs more time, so the vm will be deleted sucessfully
   before live migrate complete. And then, we will get an exception while live
   migrating.
2. After live migrate failed, we start to rollback. But, in the rollback method
   we will get or modify the info of vm from db. Because the vm has been deleted
   already, so we will get instance_not_found exception and rollback will be
   faild too.

I have two ways to fix the bug:
i)Add check in nova-api. When try to delete a vm, we return an error message if
the vm_state is LIVE_MIGRATING. This way is very simple, but need to carefully
consider. I have found a related discussion:
http://lists.openstack.org/pipermail/openstack-dev/2013-October/017454.html, but
it has no result in the discussion.
ii)Before live migrate we get all the data needed by rollback method, and add a
new rollback method. The new method will clean up resources at destination based
on the above data(The resouces at source has been already cleaned up by
deleting).

I have no idea whitch one I should choose. Or, any other ideas?:)

Regards,
wanghong
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