[libvirt] API calls to get interfaces and block devices

[Cole Robinson]

On 04/11/2014 07:14 AM, Ruben Kerkhof wrote:
> Hi all,
> 
> I have a few python scripts which use the libvirt api to get interface and block device statistics.
> What has been bugging me for a while now that is that there’s no high level api to get a list of all interfaces or block devices for a vm.
> The list can be retrieved from the xml with a bit of Xpath magic, but this seems to me to break the nice abstraction layer libvirt provides.
> Ideally, I don’t have to do anything with xml, and add dependencies on xml parsers to my code.
> 
> I’ve seen examples of code doing this, for example the collectd libvirt plugin, but there must be many others.
> 
> Can I kindly ask for such an API? Unfortunately I don’t have the skills to code this up myself.
> 

It's an unavoidable fact that XML is part of the libvirt API. Going down the
route of providing APIs that return bits and pieces of the XML is a slippery
slope and increases libvirt maintenance burden.

python has a native XML library. To do what you want is pretty straight
forward once you understand the concepts. For example this prints every
interface mac address for the VM 'f20':


import xml.etree.ElementTree as ET
import libvirt

conn = libvirt.open("qemu:///system")
dom = conn.lookupByName("f20")
xml = dom.XMLDesc(0)

root = ET.fromstring(xml)
ifaces = root.findall("./devices/interface/mac")
for iface in ifaces:
    print iface.attrib["address"]