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On Fri, Feb 27, 2015 at 08:57:53AM -0800, Dan Smith wrote:
> > Note that in the above case the libvirt driver changed the hypervisor
> > identifier despite the fact that the hypervisor had not changed, only
> > its communication endpoint.
> 
> I'd argue they're one and the same, and that's just fine. We just
> shouldn't erroneously delete things when that happens unexpectedly.

[snip]

> > A reasonable default implementation of this would be to write a uuid
> > to a file which lives with VM data and return its contents. If the 
> > hypervisor has a native concept of a globally unique identifier,
> > that should be used instead.
> 
> Those drivers shouldn't have to maintain state. And they already have a
> unique identifier: the hostname.

The hostname is a unique identifier, however, it isn't a /stable/ unique
identifier because it is determined at the whim of the administrator. We
could instead use the host UUID which is both unique and stable. That
would avoid nova having to worry about administrator reconfigurations in
this respect.  IMHO if we can make nova more robust against admin changes
like this, it'd be a good thing.  I agree that we don't want to maintain
state and indeed this is not needed - every HV I know of has a concept of
a host UUID it can report that'd do the job just fine.

Regards,
Daniel
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