[libvirt] how can dst know that migration is over?

[Daniel P. Berrange]

On Thu, Oct 22, 2009 at 05:58:30PM +0200, Dan Kenigsberg wrote:
> On Thu, Oct 22, 2009 at 12:07:49PM +0100, Daniel P. Berrange wrote:
> > On Thu, Oct 22, 2009 at 12:26:41PM +0200, Dan Kenigsberg wrote:
> > > When migrating a domain from src to dst, it first appears 'suspended' at
> > > the dst. When it's 'running', higher-level management can tell that
> > > migration is done.
> > > 
> > > However, when bugzilla.redhat.com/519204 is fixed, I can no longer count
> > > on that - migrated domain may still be suspended at the destination.
> > > 
> > > So how can I tell, at the destination, that migration is over? I could
> > > add higher-level communication from src to dst, but I am reluctant to
> > > add another failure mode. I'd rather have libvirt tell me, "hey
> > > migration is done".
> > 
> > You'll get a series of events emitted
> > 
> >  1. On destination:
> > 
> >       VIR_DOMAIN_EVENT_STARTED + VIR_DOMAIN_EVENT_STARTED_MIGRATED
> > 
> >  2. On source, if non-live migration:
> > 
> >      VIR_DOMAIN_EVENT_SUSPENDED + VIR_DOMAIN_EVENT_SUSPENDED_MIGRATED
> > 
> >  3. On source, if completed
> > 
> >      VIR_DOMAIN_EVENT_STOPPED + VIR_DOMAIN_EVENT_STOPPED_MIGRATED
> > 
> >  4. On source, if aborted & non-live 
> > 
> >      VIR_DOMAIN_EVENT_RESUMED + VIR_DOMAIN_EVENT_RESUMED_MIGRATED
> > 
> >  5. On destination, if successful
> > 
> >      VIR_DOMAIN_EVENT_RESUMED + VIR_DOMAIN_EVENT_RESUMED_MIGRATED
> > 
> >  6. On destination if failed
> > 
> >      VIR_DOMAIN_EVENT_STOPPED + VIR_DOMAIN_EVENT_STOPPED_FAILED
> > 
> 
> oh, so the 'detail' parameter is not just an ornament..

NB, this example is specifically for the QEMU driver, the detail parameter
is not guarenteed to match this for all drivers. eg, the Xen driver is
unable to distinguish the different causes of events. So all RESUMED
events will have VIR_DOMAIN_EVENT_RESUMED_UNPAUSED. We do best effort to
get the most accurate detail possible.

Daniel
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