[Libvir] default hypervisor selection

[Daniel Veillard]

On Thu, Feb 21, 2008 at 02:36:10PM +0000, Daniel P. Berrange wrote:
> On Thu, Feb 21, 2008 at 09:26:38AM -0500, Daniel Veillard wrote:
> >  What do people think ? I would be tempted to provide a patch to change
> > do_open() behaviour on linux in the case name is NULL or "", and 
> > then check what hypervisor might be present and running,
> 
> I think it is worthwhile - the 'default to Xen' behavious is a major cause 
> of pain for people initially using libvirt, particularly since KVM is
> becoming the defacto standard for Linux platforms. I'd see the following
> levels of customization:
> 
>   - If a non-NULL  URI is passed in virConnectOpen, use that
>   - Else if LIBVIRT_DEFAULT_URI is set use that URI
>   - Else probe each registered driver in order until one succeeds
> 
> For the latter I think we could add a 'probe' method to the internal driver
> API table. Then we can just call 'probe' on each driver in turn until we 
> find one which is  available on the system. 

  Yup, that's even better than ad-hoc attempt at detecting, it really should
go in the driver.

> At the same time it could be worth having a public API to 'detect drivers'
> which will call probe for each driver and return a list of all drivers
> which are available. This allows an app to easily ask libvirt what it
> supports - because long term we'll definitely get hosts supporting many
> drivers at once.  We can also advertise this list of supported drivers
> using the Avahi mDNS broadcasts we do from the remote daemon.

  That can be done in a second step, less urgent IMHO but useful too,

Daniel

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