Comment 2 for bug 1535918

We discussed this issue at the mid cycle. They asked the PowerVM team to re-evaluate because this works in libvirt. What is different in PowerVM's implementation.

I believe both drivers have the same semantic for rebuild/evacuate. The instance is destroyed on the source system and then the spawn is run on the target host. This is the compute manager's default implementation.

The next question was what was different about our criteria to determine if the vif plug time out should be adhered to.

PowerVM's implementation is pretty simple:

        if (utils.is_neutron() and CONF.vif_plugging_timeout):
            return [('network-vif-plugged', vif['id'])
                    for vif in self.network_info
                    if vif.get('active', True) is False]
        else:
            return []

Libvirt's is:
        timeout = CONF.vif_plugging_timeout
        if (self._conn_supports_start_paused and
            utils.is_neutron() and not
            vifs_already_plugged and power_on and timeout):
            events = self._get_neutron_events(network_info)
        else:
            events = []

In a rebuild scenario, the libvirt should hit this.
 - self._conn_supports_start_paused: True if KVM or QEMU
 - utils.is_neutron(): assumed to be true.
 - vifs_already_plugged: False (in that this is a rebuild)
 - power_on: True (in that this is a rebuild)
 - timeout: Assumed to be set to some number.

I guess I'm wondering if libvirt could be affected by this bug? It could be hitting this, but then passing a rebuild test case if the CONF.vif_plugging_is_fatal is set to False.

Another reason that libvirt may not be impacted is perhaps they are doing an instance.save elsewhere in the flow. Thus inadvertantly updating to the right host. But I don't believe this to be the case...it looks like the only places instance.save is called is in cleanup and in the _live_migration_monitor. Also, nothing in the driver is updating the host, that is done solely in the manager (as one would expect).

Kyle - did I mis-interpret the issue?