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On 05/21/2015 03:20 PM, Mathieu Gagné wrote:
> On 2015-05-21 3:13 AM, Daniel P. Berrange wrote:
>> On Thu, May 21, 2015 at 09:34:20PM +1200, Xav Paice wrote:
>>> On 21/05/15 21:23, Daniel P. Berrange wrote:
>>>> On Wed, May 20, 2015 at 03:01:50PM -0700, Michael Still wrote:
>>>>> I note that we use instance.name to lookup the libvirt domain a bunch
>>>>> in the driver. I'm wondering why we don't just use instance.uuid all
>>>>> the time -- the code for that already exists. Is there a good reason
>>>>> to not move to always using the uuid?
>>>>>
>>>>> I ask because instance.name is not guaranteed to be unique depending
>>>>> on how weird the nova deployment is.
>>>> Agreed, there's no benefit to using name - internally libvirt will always
>>>> prefer to use the UUID itself too.
>>>>
>>>> These days though, there is only a single place in nova libvirt driver
>>>> that needs updating - the nova.virt.libvirt.host.Host class get_domain()
>>>> method just needs to be switched to use uuid.
>>>
>>> Just a comment from an ops point of view - it would be miles easier when
>>> trying to troubleshoot, if the instance name was the uuid anyway.  I
>>> totally agree on using instance.uuid, just to comment that I find it a
>>> little painful sometimes that instance names don't match the uuid of the
>>> instance, but the directory structure does.  Just a bit of confusion to
>>> avoid at 2am when something isn't working.
>>
>> You do know you can configure the instance name used...
>>
>> eg in nova.conf
>>
>>    instance_name_template='inst-%(uuid)s'
>>
>
> Please note that you CANNOT change instance_name_template ones instances
> are created otherwise they become unmanageable by Nova. This is because
> Nova tries to find the libvirt instance by its name instead of its UUID.
> So since instances were spawned with the old value, it won't find
> existing instances using the new value.
>
> And no, I haven't found a way to rename an instance without
> redefining/restarting it in libvirt.

Is there any reason why we couldn't default to using something like 
'inst-%(uuid)s' for the instance name?

Chris