Re: [Qemu-devel] [RFC] QEMU Dbus support - a proposal management API

["Richard W.M. Jones" <rjones@redhat.com>]

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Anthony Liguori wrote:
> Daniel P. Berrange wrote:
>> Or have 2 monitor interaction modes. One mode uses the command line style
>> suitable for people / scripting languages. The other umode ses a 
>> binary XDR
>> protocol for serializing the args & returns values for formal control
>> APIs to use in a easy manner. It ought to be reasonably 
>> straightforward to
>> add a binary serialization format for all existing commands
>>   
> 
> I don't think binary is inherently easier to parse than text provided 
> that some thought is put into the format of the textual output.

XDR (aka RFC 1014 & RFC 4506) does let you generate complex interfaces 
with relative ease.  For example, here's the description of the remote 
protocol used by libvirt:

http://git.et.redhat.com/?p=libvirt.git;a=blob;f=qemud/remote_protocol.x;h=d409c74387c2642651896136aba9bc1e2b62b621;hb=HEAD

"Parsing" is done for you by stubs that are generated from the above file.

On the downside it turns out that it's not very well supported under 
Windows.  For libvirt I had to basically port an XDR implementation by 
hand to MinGW and add extra functions from glibc to it.

> I think we just want to levels of verbosity.

This would work too.

On the point of controlling multiple qemu instances on a machine from a 
single place: Easiest way to do this would be to direct all the monitor 
sockets into a single known directory.  Something along the lines of:

   qemu -monitor unix:/var/lib/qemu-monitors/`uuidgen`,nowait

A control process can then just keep an eye on entries under that 
directory, and (unlike libvirtd) it's robust against the control process 
restarting.

Rich.

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