Open Stack

On 2015-05-21 3:38 PM, Chris Friesen wrote:
> 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?
> 

I guess it's for the reason I mentioned above:

To not break all OpenStack installations on Earth running with default
config values.

-- 
Mathieu