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Date: Mon, 23 Nov 2009 07:11:53 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 00/10]: QError v4
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To: Luiz Capitulino <lcapitulino@redhat.com>
Cc: kraxel@redhat.com, Markus Armbruster <armbru@redhat.com>, qemu-devel@nongnu.org

Luiz Capitulino wrote:
> On Sun, 22 Nov 2009 10:08:16 -0600
> Anthony Liguori <anthony@codemonkey.ws> wrote:
>
>   
>> I'm certainly willing to consider alternative ways to do qmp_error() but 
>> taking a free form string is not an option in my mind. It goes against 
>> the fundamentals of what we're trying to build with QMP.
>>     
>
>  Agreed.
>
>   
>> So if you're opposed to structured error data, just having 
>> qmp_error(error_code) is a reasonable alternative. I don't think it's 
>> the right thing to do, but I think it's still within the spirit of the 
>> goals of QMP.
>>     
>
>  You mean, we would have calls like:
>
> qemu_error_new(error_code, 'device '%s' not found', name);
>   

Except drop the 'device %s not found' bit.

>  and on the wire:
>
> { "error": 1234 }
>
>  Did I get it right?
>
>  If so, I can see some problems with it:
>
> 1. It's impossible to know what 1234 means by watching the
>    protocol on the wire. Although this is a machine protocol,
>    this is a good feature
>
> 2. We may have errors where having the error data is needed,
>    and iirc someone gave an example of this some hundreds
>    of emails ago
>
> 3. A new error will require a new code. Classes have the
>    advantage of becoming stable over time and we'll end up
>    just automatically reusing existing ones
>   

Yes, this is why I'm happy with the current state of QError.  We address 
all of these problems nicely :-)

Regards,

Anthony Liguori