[libvirt] Remotable Libvirt

[Stef Walter]

On 07.06.2017 07:49, Martin Pitt wrote:
> Hello Richard,
> 
> Richard W.M. Jones [2017-05-31 18:00 +0100]:
>> I agree with others that as things stand you will need a REST or DBus
>> or similar API added to libvirt.
>>
>> However have you considered using gobject-introspection to generate
>> new "Payload" types automatically?
> 
> This doesn't fundamentally change the picture here. Our JavaScript runs in the
> browser, so on that side GI doesn't help. What we could do is to dynamically
> create some code in the Cockpit module, send it over to the remote machine, and
> have it be executed. This could be in Python, which then assumes that
> python-libvirt is installed there, or in JS which then assumes that
> libvirt-glib and gjs are installed. The latter seems like a stronger
> assumption on a server even, but structurally these are pretty similiar.
> 
> I. e. GI is not a magic thing to make an API remotable, it just makes it
> bindable to different programming languages.
> 
> C/GI interfaces also don't map well to D-Bus, i. e. it's not practical to
> autogenerate a D-Bus interface for a given GI API. This still works for the
> most simple methods that only accept primitive data types and strings, but as
> soon as you pass any structs, pointers, function pointers etc. around this
> can't be exposed though D-Bus any more without further interpretation on the
> server side.

Perhaps not an runtime. But it seems like such a thing could be done at
compile time for the libvirt C API. The libvirt folks do it for their
python bindings, using code generation.

The libvirt Python API behaves a lot like the C API. It's very flat and
not very "pythonic". Which is actually a nice target for us. We could do
something similar with a simple "flat" DBus wrapper of the API ... using
code generation.

What do you think?

Stef


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