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Date: Tue, 23 Jun 2009 13:32:37 -0500
From: Anthony Liguori <aliguori@us.ibm.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 01/11] QMP: Introduce specification file
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To: Avi Kivity <avi@redhat.com>
Cc: ehabkost@redhat.com, jan.kiszka@siemens.com, dlaor@redhat.com, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>, Vincent Hanquez <tab@snarc.org>

Avi Kivity wrote:
>
> An RPC makes it a lot easier for clients to parse, there's no need for 
> a regular expression per command, or to bother with line continuations 
> etc.  You just focus on the data.
>
> We have an opportunity to make a clean break, let's make use of it.

If we structure things internally correctly, by having a flow that 
basically looks like:

int <monitor_command>(Monitor *mon, <args>)
{
   // process args
   if (success) {
       monitor_print_data(mon, <highly structured output>);
    } else {
       record_extended_error(<message>);
       return error_code;
    }
}

Then it that works well for both the human monitor and the computer 
monitor.  It's an RPC though.

Should we support other types of RPCs?  I don't know.  I'd think that 
you could create a computer monitor -> jsonrpc bridge easily enough.

If we implement this correctly, then an RPC interface could just be 
another option to see the computer monitor mode implemented as a "module".

>> I don't want to invent Xen-API here and go through that pain in QEMU.
>
> I don't see the parallel.

Xen-API was the "clean break" for Xend.

-- 
Regards,

Anthony Liguori