[libvirt] Remotable Libvirt

[Daniel P. Berrange]

On Tue, Jun 06, 2017 at 05:11:55PM +0200, Peter Krempa wrote:
> On Tue, Jun 06, 2017 at 07:45:10 -0700, Peter wrote:
> > On 05/26/2017 02:11 AM, Martin Kletzander wrote:
> > > On Thu, May 25, 2017 at 10:16:26AM -0700, Peter Volpe wrote:
> 
> [...]
> 
> > > If we standardize even the smallest part of the RPC, then it might screw
> > > us immediately.  We are keeping it private just so we can enhance the
> > > APIs we already have.  We don't know when we will need to change some
> > > part of it.
> > > 
> > 
> > How does the current ssh implementation work?
> > (https://libvirt.org/remote.html) If clients are able to talk to a remote
> > libvirtd via ssh then there must be some sort of compatibility guarantee.
> > Otherwise unless the versions are exactly the same clients wouldn't be able
> > to talk to remote daemons.
> 
> They use the internal RPC protocol transported over SSH. The client
> library initializes the ssh connection to the server, and then starts to
> talk the RPC tunelled over the SSH session.
> 
> The compatibility is guaranteed only if you use the client library. As
> said, the RPC protocol is considered an internal detail and the client
> library shields you from a possible incompatibility if we'd ever make
> incompatible change.

Ignoring wire compatibility questions, it is important to note that not all
functionality in libvirt is done in libvirtd. There are libvirt drivers that
are entirely implemented in the library, not libvirtd. For some of the
libvirt drivers that do use libvirtd, there is also still some functionality
that is client side.

Regards,
Daniel
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