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On Thu, Apr 13, 2017, at 12:45 PM, Matt Riedemann wrote:
> This came up in the nova/cinder meeting today, but I can't for the life 
> of me think of why we don't unbind ports or terminate the connection 
> volumes when we shelve offload an instance from a compute host.
> 
> When you unshelve, if the instance was shelved offloaded, the conductor 
> asks the scheduler for a new set of hosts to build the instance on 
> (unshelve it). That could be a totally different host.
> 
> So am I just missing something super obvious? Or is this the most latent 
> bug ever?

It's at the very least a hack, and may be a bug depending on what
behaviour is being seen while the instance is offloaded or unshelved.

The reason that networks and volumes are left in place is because it
is/was the only way to prevent them from being used by another instance
and causing a subsequent unshelve to fail. During the unshelve operation
it is expected that they will then be shifted over to the new host the
instance lands on if it switches hosts.

This is similar to how resize is handled.  From an implementation point
of view you can think of shelve as being a really really long
resize/migration operation.

There very well may be issues with this approach.

> 
> -- 
> 
> Thanks,
> 
> Matt
> 
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