Re: [Engine-devel] API design and plan
On Tue, Dec 06, 2011 at 02:58:59PM +0200, Dan Kenigsberg wrote:
On Mon, Dec 05, 2011 at 11:34:18AM -0600, Adam Litke wrote:
> Hi everyone. On today's VDSM call we discussed the requirements, design, and
> plan for updating the API to include support for QMF and single-host REST API.
> All members present arrived at a general consensus on the best way to design the
> next-generation API. I have tried to capture this discussion in the oVirt wiki:
>
> http://ovirt.org/wiki/Vdsm_API
>
> Please take a look at this page and let's discuss any changes that may be
needed
> in order to adopt it as a working plan that we can begin to execute. Thanks!
>
Very nice, I've fixed two bullets about the future of the xml-rpc.
Thanks... Updates look good to me.
I think that we are missing something here: how do we model
Vdsm-to-Vdsm
communication, in a binding-blind way? I'm less worried about the
storage-based mailbox used for lvextend requests: my problem is with
migration command.
Ok, interesting... Besides migration, are there other features (current or
planned) that would involve P2P communication? I want to ensure we consider the
full problem space.
Currently, the implementation of the "migrate" verb
includes contacting
the remote Vdsm over xml-rpc before issuing the libvirt migrateToURI2
command ('migrationCreate' verb).
A Vdsm user who choose to use the REST binding, is likely to want this to
be implemented this using a REST request to the destination. This means
that the implementation of Vdsm depends on the chosen binding.
The issue can be mitigating by requiring the binding level to provide a
"callback" for migrationCreate (and any other future Vdsm->world requests).
This would complicate the beautiful png at
http://ovirt.org/wiki/Vdsm_API#Design ... Does anyone have another
suggestion?
Actually, I think you are blending the external API with vdsm internals. As a
management server or ovirt-engine, I don't care about the protocol that vdsm
uses to contact the migration recipient. As far as I am concerned this is a
special case internal function call. For that purpose, I think xmlrpc is
perfectly well-suited to the task and should be used unconditionally, regardless
of the bindings used to initiate the migration.
So I would propose that we modify the design such that we keep an extremely thin
xmlrpc server active whose sole purpose is to service internal P2P requests.
--
Adam Litke <agl(a)us.ibm.com>
IBM Linux Technology Center