[occi-wg] OCCI MC - State Machine Diagram

[Chris Webb]

Andre Merzky <andre at merzky.net> writes:

> Quoting [Michael Richardson] (Apr 20 2009):
> > 
> > >>>>> "Andre" == Andre Merzky <andre at merzky.net> writes:
> >     Andre> For example, assume that I have a client which implements the
> >     Andre> core specification only, thus only knows the STOPPED, ACTIVE
> >     Andre> and SUSPENDED states (your original figure).  What is that
> >     Andre> client supposed to do if the backend reports an PAUSED state?
> > 
> >   How did it get to that state?
> >
> >   Since the client didn't put it into that state, it means that an
> > operator or error must have forced this, so it's an error.  Life does
> > not always go as planned.
> 
> It is dangerous to assume that the client is the only
> legimitate entity which operates on the machine state
> diagram.  The system admin, internal events, other clients,
> etc, may all have reason to trigger state changes, and this
> would not represent errors.

A concrete example: guests operating systems on our platform can already do
an ACPI power down, terminating the running virtual machine. This is a
state change which happens without an API call, but not an error state.

Similarly, if a guest operating system suspends or hibernates in a way
that's visible to the hypervisor (say ACPI S3/S4 sleep), a future version of
our platform will probably transition the virtual machine process itself
into a paused, suspended or dumped-to-disk state.

Cheers,

Chris.