compute pollster uses internal nova libvirt connection API

[Eoghan Glynn]

The compute pollster depends on the nova libvirt connection '_conn' atribute, which looks like a potentially problematic usage of an internal nova API which may be open to change without notice.

This usage should be replaced with an agreed stable API.

[Doug Hellmann (doug-hellmann)]

It looks like what we need is a way to get the domain data from the connection so we can pull out values from the XML. Do we want the API to give us the raw data, or should we add an API to get the stats we want so other hypervisors can implement those new calls and integrate with us more easily?

$ grep _conn ceilometer/compute/libvirt.py
def get_libvirt_connection():
        return nova.virt.connection.get_connection(read_only=True)
        domain = conn._conn.lookupByName(instance)
            conn = get_libvirt_connection()
        conn = get_libvirt_connection()
        domain = conn._conn.lookupByName(instance.name)
        conn = get_libvirt_connection()
            domain = conn._conn.lookupByName(instance.name)

$ grep domain ceilometer/compute/libvirt.py
        domain = conn._conn.lookupByName(instance)
        tree = etree.fromstring(domain.XMLDesc(0))
        domain = conn._conn.lookupByName(instance.name)
        tree = etree.fromstring(domain.XMLDesc(0))
            domain = conn._conn.lookupByName(instance.name)
                    domain.interfaceStats(vnic['name'])

[Julien Danjou (jdanjou)]

We should add an API to get the stats we want so other hypervisors can implement those new calls and integrate with us more easily.