Re: [Xen-devel] RFC: "local" communications

[Nivedita Singhvi <niv@xxxxxxxxxx>]

Anthony Liguori wrote:
> Rik van Riel wrote:
>
> > Hi,
> >
> > When combining clustering with cluster storage, the situation
> > arises where virtual machines are not only managed by the cluster
> > software, but also need to participate in the cluster software
> > themselves...
> >
> > In order for this to work better, it would be good if there
> > was a way for software in a domU to communicate with software
> > on the local dom0 - so after being migrated elsewhere, a guest
> > would start talking to the new dom0 automatically.
Rik, is this a heartbeat kind of protocol or some such thing?
Is there value to making it be a generic solution that would
work when communicating in a non-xen environment?

> > Should it be some virtual device analogous to the virtual
> > network driver, or should we have some other kind of socket
> > for node local communications ?
Using protocols like TCP for node-local comms is undesirable
as TCP is engineered for the heavy machinery of the Internet.
UDP or raw sockets will be somewhat better, although AF_UNIX
would be best of all (albeit with its own constraints).

> > What kind of approach would the Xen community (that's you, if
> > you read this far) prefer ?
> >  
> I can only speak for myself, but I'd personally like to see a small 
> userspace library that established a datagram connection between two 
> domains (using an event channel and a shared page) that could be reused 
> for many applications.
Which datagram service, Anthony?  Having a small lib like this
would be a good idea, although the benefit would be in the details,
and of course, depending on how many apps we need to support that
we don't want to modify...

> If it could be used with normal read/write calls that would be even 
> better (although first thought is that that would require a daemon).
Probably don't want to do that...

thanks,
Nivedita

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