Re: [PATCH v2 01/27] migration: Network Failover can't work with a paused guest

[Michael S. Tsirkin]

On Thu, Dec 03, 2020 at 12:06:14PM +0000, Daniel P. Berrangé wrote:
> > > It isn't really about the admin.  It is about countless existing mgmt apps
> > > that expect migration will always succeed if the VM is paused. The mgmt
> > > apps triggering the migraiton is not neccessarily the same as the app
> > > which introduced the use of NIC failover in the config.
> > > 
> > > eg in OpenStack Nova provides the VM config, but there are completely
> > > separate apps that are built todo automation on top of Nova which 
> > > this is liable to break. There's no human admin there to diagnose
> > > this and re-try with unpause, as all the logic is in the apps.
> > > 
> > > 
> > > Regards,
> > > Daniel
> > 
> > So let's say pause fails. Won't this break these theoretical apps?
> 
> Yes, they are broken in a way that can now actually be seen, as opposed
> to just hanging forever in migration.

Right but there are countless apps out there, and they are all broken,
maybe not too hard to debug if one knows where to look, but still ...

And again only true for pause then migrate, migrate then pause is still
broken, and if we fix it by failing pause then no one knows whether apps
are prepared to handle a failure in the pause command, previously if
used correctly it would never fail I think ...

-- 
MST