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Re: [libvirt] [PATCH] Allows for a <description> tag for domains



On Wed, Sep 30, 2009 at 02:58:07PM +0200, Daniel Veillard wrote:
>   https://bugzilla.redhat.com/show_bug.cgi?id=523639
> 
> feature request which makes sense to me, the simple patch attached
> seems to be sufficient, one can define and have the description back
> in the dump. Doesn't try to keep the location of the tag, it always
> get serialized after <uuid>.
> The only drawbacks I can think of are:
>   - others XML formats may require the same, but honnestly it's trivial

I wonder if there's any value in putting it inside a <metadata>
element, so if we add more official metadata fields those can be
grouped in the same place. It also helps to make it clear that
it is not going to have a functional effect on the domain like
the rest of the elements do. 

If a hypervisor backend only had a single 'description' field in its
native config format, we  could even consider the storing the entire
<metadata> element in that one description field allowing encoding
of arbitrary metadata beyond that supported by the HV in question.

>   - machine generated description (for example if the history log of
>     a domain gets stored there) could grow a lot and I wonder if we
>     have a hard limit on the size when transmitting xml descriptions

The remote protocol has a arbitrary 256 KB limit on all data in a
single message:

  const REMOTE_MESSAGE_PAYLOAD_MAX = 262120;


We can increase that limit at any time we like without impacting
ABI - its just a limit to avoid denial of service attacks from
stupidly large messages

Daniel
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