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Re: [libvirt] [RFC] Unify KVM kernel-space and user-space code into a single project



Daniel P. Berrange wrote:
> On Fri, Apr 09, 2010 at 03:31:37PM +0100, Antoine Martin wrote:
>> [snip]
>>>> * not everything is exposed via libvirt:
>>>> virsh can retrieve vncdisplay
>>>> but libvirt (or at least the python bindings) does not. How come?
>>>> This happens to be one thing I need for writing a libvirt backend for my
>>>> virtual desktop software.
>>> The 'virsh vncdisplay' command is simply fetching the XML doc for the
>>> guest and then extracting the VNC port using a xpath expression
>>>
>>>    /domain/devices/graphics[ type='vnc']/@port
>>>
>>> So for python you'd want to just get an XML handling module and do similar.
>> Yes, I saw that in the virsh code.
>> Shouldn't this be part of the libvirt api proper??
>> Isn't it supposed to shield us from dealing with files and XML?
> 
> It isn't scalable to add APIs for extracting each possible piece of info
> from the XML. All languages have APIs for extracting data from XML using
> XPath (or DOM). Thus it is better to leave that flexibility to the apps
> rather than hardcoding APIs for it in libvirt. The XML schemas/docs are
> a formal part of the libvit API, so we're not trying to sheild that from
> apps.
> 
I was thinking of something like:
domain.get_attribute("vncdisplay")

Because it's a shame to have to use virsh as a wrapper (or XML file
parsing) and re-do all the work that was done to get to the domain
object when all your really want is just an attribute..

Cheers
Antoine


> Regards,
> Daniel


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