> -Original Message-
> From: Paul Carlton [mailto:paul.carlt...@hpe.com]
> Sent: Tuesday, November 10, 2015 4:51 PM
> To: OpenStack Development Mailing List (not for usage questions)
> Subject: [openstack-dev] [nova] live migration management approach
>
> All
>
> I inherited the task of producing an upstream spec for querying and aborting
> ongoing migrations from a co-worker and submitted a new spec
> https://review.openstack.org/#/c/228828//. A related spec for pausing an
> instance being migrated to enable the migration to complete is also proposed
> https://review.openstack.org/#/c/229040/.
>
> However I am now wondering if building these capabilities around the
> migration object is the right way to go. I'm now wondering if this is right
> way
> to approach this or whether it would be better to implement some additional
> operations on hte instance object?
>
> I'm become aware that details of the progress of a migration operation is
> already available to both cloud admins and instance owners via the server
> get
> details operation, which reports the progress of migration.
>
> Cancelling a migration could be implemented as a reset-task operation on an
> instance?
Reset-task operation would mean that we need to raise exceptions (bad request
or whatever else) for almost every vm task. How many of them are really
cancelable? Also I have a feeling that it is live migration related action so
current approach is ok with me.
> The proposal in https://review.openstack.org/#/c/229040/ relates to
> providing the facility to pause an instance that is being migrated so that
> the
> migration can complete (i.e. in the case where the instance is dirtying
> memory quicker than the migration processing can copy it).
> This could be implemented by simply allowing the existing pause operation
> on a migrating instance. The existing implementation of live migration
> means
> that the instance will automatically resume again when the migration
> completes. We could amend instance pause so that it issues a warning if a
> pause operation is performed on an instance that has a task state of
> migrating so the user is made aware that the pause will only be temporary.
My personal feeling is that we should not reuse the same operation for two
different purposes. IMHO pause operation should be as it is - operator pauses
an instance and it remains paused also after live migration completion. Such
case is valid from user perspective who might not be aware of ongoing live
migration. However, this might require some work in Libvirt, not sure we can
do it without changing/adding new Libvirt behavior.
Kind Regards,
Pawel Koniszewski
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