Re: [Libvir] RFC: get/set properties
On Tue, Apr 15, 2008 at 11:31:32AM -0700, Ryan Scott wrote:
I'd like to get some comments on the following...
We would like to use libvirt to store some properties related to a
domain. This can be done by adding a simple get/set API as follows:
What are the properties ? I'm not really very enthusiastic about the
idea of adding API / XML for generic key,value properties. I think it
will quickly be abused as a way to add arbitrary, non-standardized
hypervisor / driver specific configuration which would be better
represented with explicit schema.
/*
* Domain property get/set interfaces
*
* For GetProp, the return value must be freed by the caller.
*/
char * virDomainGetProp (virDomainPtr domain,
const char *propName);
int virDomainSetProp (virDomainPtr domain,
const char *propName,
const char *value);
The XML would look something like this:
virsh # dumpxml solaris-pv-0
<domain type='xen' id='-1'>
[ snip ]
<properties>
<blah value="3"/>
<foo value="bar"/>
</properties>
</domain>
One of the key ideas behind libvirt is that we try to provide a consistent
set of configuration options across all drivers. NB, I'm not saying we need
the lowest-common denominator - just that we try to formalize a way to
represent every configuration option in such a away that it could be applied
to any driver. I don't think simple key,value pairs are sufficient in the
general case.
As an example, you could define a property 'console' which takes a pty path
as its value. But if you want to generalize this to different types of
console access, then a single value becomes insufficient.eg need a host+port
for a console accessed over TCP. The more explicit specialized <console>
tag allows us the flexibility of adding attributes and sub-elements as
needed, not restricting ourselves to key,value pairs.
Dan,
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