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I would block it in the API or have the API cancelling the migration first. 
I don't see a reason why to start an operation that is meant to fail, which also has a complex chain of event, following it failure.

Regardless of the above, I think that the suggested exception handling is needed in any case.


Vladik    

----- Original Message -----
> From: "Loganathan Parthipan" <parthipan at hp.com>
> To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org>
> Sent: Monday, 16 December, 2013 8:25:09 AM
> Subject: Re: [openstack-dev] [Nova][libvirt]when deleting instance which is in migrating state, instance files can be
> stay in destination node forever
> 
> 
> 
> 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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