[libvirt] [PATCH alt] conf: Allow user define their own alias

[Michal Privoznik]

On 09/29/2017 10:49 AM, Daniel P. Berrange wrote:
> On Fri, Sep 29, 2017 at 09:06:01AM +0200, Michal Privoznik wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1434451
>>
>> It comes handy for management application to be able to have a
>> per-device label so that it can uniquely identify devices it
>> cares about. The advantage of this approach is that we don't have
>> to generate aliases at define time (non trivial amount of work
>> and problems). The only thing we do is parse the user supplied
>> tag and format it back. For instance:
>>
>>     <disk type='block' device='disk'>
>>       <driver name='qemu' type='raw'/>
>>       <source dev='/dev/HostVG/QEMUGuest1'/>
>>       <target dev='hda' bus='ide'/>
>>       <alias user='myDisk0'/>
> 
> I really do not like this - having two arbitrary string alias names is
> just crazy. 

Why is that? We have plenty of elements that do not match to anything at
hypervisor level. Firstly, there's metadata. Secondly, aliases in lxc
driver don't match anything either. And one can argue that the link in
qemu can be broken too. I mean, it's just for now that the aliases we
report happen to be device IDs we put onto the qemu's cmd line. Not to
mention devices that we put there and not report in the domain XML => no
IDs visible there.

> If we want to add a second attribute to uniquely identify
> devices, then it should be a UUID IMHO, so it at least has some tangible
> benefit instead of just duplicating the existing id format

I'm failing to see why UUID is better than any arbitrary string. You
mean we would generate the UUIDs if not supplied by user?

Michal