Re: [Qemu-devel] [RFC V3 3/7] qapi: Add skeletton of command to query a drive bs graph.

[Benoît Canet]

Le Thursday 05 Dec 2013 à 07:59:22 (-0700), Eric Blake a écrit :
> On 12/05/2013 07:43 AM, Benoît Canet wrote:
> 
> >> There's one case where management might not know - if libvirtd gets
> >> restarted while in the middle of an operation that was attempting to
> >> create a named node, then on restart and reconnection to the monitor,
> >> libvirt would want to query to see if the node actually got created or
> >> if the command needs to be attempted again.  I'm not a fan of write-only
> >> interfaces - and making management responsible to track all named nodes
> >> with no way to query if qemu actually agrees with the topology that
> >> management thinks it has commanded feels like a write-only interface.
> > 
> > Would a command returning info about a specific named node be sufficient for
> > libvirt checks ?
> > It's far less complex to implement than exposing the whole graph.
> > We could also provide a simple command to list the names of the named nodes.
> 
> Yes, both of those ideas are useful; it still means management must
> track the topology between the nodes, but it at least gives management
> enough control to know which set of nodes exist to confirm which
> operations have occurred.

I will start by implementing the named nodes name list first.
Don't worry for the other solution: my customer want crypto filters and multi
BlockDriver state throttling as a filter so I will continue to enable filter
in a progressive way.

Best regards

Benoît
> 
> -- 
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>