[nova][ops] Trying to get per-instance live migration timeout action spec unstuck

Matt Riedemann mriedemos at gmail.com
Fri Jan 4 00:02:16 UTC 2019

On 1/3/2019 5:45 PM, Dan Smith wrote:
> You can't abort a post-copy migration once it has started. If we were to
> add an "always do post-copy" mode to Nova, per the recommendation from
> the post I linked, then we would start a migration in post-copy mode,
> which would make it un-cancel-able. That means not only could you not
> cancel it, but we would have to refuse to start the migration if the
> user requested an abort action via this new proposed API with any
> timeout value.
> Anyway, my point here is just that libvirt already (but not nova/libvirt
> yet) has a live migration mode where we would not be able to honor a
> request of "abort after N seconds". If config specified that, we could
> warn or fail on startup, but via the API all we'd be able to do is
> refuse to start the migration. I'm just trying to highlight that
> baking "force/abort after N seconds" into our API is not only just
> libvirt-specific at the moment, but even libvirt-pre-copy specific.

OK, sorry, I'm following you now. I didn't make the connection that you 
were talking about something we could do in the future (in nova) to 
initiate the live migration in post-copy mode. Yeah I agree in that case 
if the user said abort we'd just have to reject it and say you can't do 
that based on how the source host is configured.




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