[Ovirt-devel] [PATCH server] Rake task to generate a dot drawing of the possible VM states

[Ian Main]

On Tue, 06 Jan 2009 17:07:20 -0800
David Lutterkort <lutter at redhat.com> wrote:

> I was curious what all the VM state transitions taken together look like
> - below is a rake task that generates a dot drawing of the FSM of VM
> states.
> 
> Attached is a picture of all that for everybody's amusement.
> 
> David

Wow, that's pretty neat!  Pretty graph.

I must say however that these states don't really reflect the states provided
by libvirt.  Libvirt has no sense of intermediate states like 'starting', 'migrating'
etc.  There's also no distinction regarding 'saved' state vs stopped.  'saved' is
merely a stopped vm that has had an image taken of it.

I know the 'starting' etc. is mostly for user feedback and also to prevent race
conditions where you can try to start a vm multiple times.  However while testing
the taskomatic changes I was able to queue 5 or so 'start_vm' tasks just because
the UI was slow to update (I kept pressing the button and it lagged but queued
them all).

So anyway, I'm not sure about these intermediate states, and the 'saved' state is
actually broken..  something we'll have to remember to fix.  The intermediate states
present a problem in that you can get out of sync with what db-omatic and even
taskomatic know the real libvirt state to be if you are not careful.

	Ian