[libvirt] [PATCH] blockjob: use stable disk string in job event

Adam Litke alitke at redhat.com
Mon Jun 16 17:58:00 UTC 2014


On 16/06/14 09:52 -0600, Eric Blake wrote:
>On 06/16/2014 09:45 AM, Daniel P. Berrange wrote:
>> On Sat, Jun 14, 2014 at 07:49:40AM -0600, Eric Blake wrote:
>>>
>>> If you think backward compatibility of old clients that expected
>>> and operated on an absolute name is too important to break, I'm
>>> open to suggestions on alternatives how to preserve that. We don't
>>> have a flag argument during event registration, or I would have
>>> used it.  Otherwise, I hope this change is okay as-is.
>>
>> Hmm, I fear this is one of those cases where it seems fine
>> to change the semantics, but is liable to bite us later.
>>
>> The most obvious alternative is to just introduce a new event
>> BLOCK_JOB_EVENT_2 or something less sucky. That still leaves
>> the question of how to generate the old event in the fact of
>> a disk with no local name - we could use empty string '' as
>> the "path" if the disk lacks one. Or we could simply not emit
>> the old style event. I'd probably go for empty string though.
>
>Adam was the one that brought this issue up in the first place. Adam,
>would you be okay registering for a new event id that guarantees you get
>a stable name?

Yeah, this would be fine for me.

>
>Libvirt would have to be able to generate both old and new style events
>(yuck for me to code up, but such is life of back-compat), but Dan has a
>valid point that the change is subtle enough that it might bite us if we
>don't have some way to get both the old and the new style event by
>explicit user request.
>
>-- 
>Eric Blake   eblake redhat com    +1-919-301-3266
>Libvirt virtualization library http://libvirt.org
>



-- 
Adam Litke




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