Re: [Qemu-devel] [PATCH V11 09/17] qmp: add interface query-snapshots

[Eric Blake]

On 04/11/2013 09:17 PM, Wenchao Xia wrote:

>>
>>> Hmm, as I typed that, I did another search of qemu-schema.json - we have
>>> the type 'ImageInfo' defined, but none of the existing 'command's ever
>>> call out the use of that type.  Is it a type we are only using
>>> internally to date, and where this is the first QMP command that would
>>> actually expose SnapshotInfo or ImageInfo to a management app?  Then
>>> maybe we _CAN_ modify SnapshotInfo, clean up all the internal code, and
>>> provide a saner type for the first time that QMP can actually use it.
>>
>> IIRC, it's being used by qemu-img. As it's not trivial to determine if
>> the field has users and as what goes in the schema is to be considered
>> stable,
>> it's better to keep the field. Instead, we could add a better field and
>> deprecate the current one.
>>
>   I remember there is a patch laster year made "qemu-img info" dump out
> json strings, where vm-clock-sec is dumped out.

Ah, so it's not QMP exposing it, but qemu-info in JSON mode.  Still,
changing that output to delete a field might break existing tools;
adding a field might be safer, but then you'd have redundant information
in the old style for old tools, as well as the added field.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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