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

[Eric Blake <eblake@redhat.com>]

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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.

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


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