Re: [Qemu-devel] [PATCH 03/22] qapi: add Error object

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/07/2011 05:06 AM, Daniel P. Berrange wrote:
> On Sun, Mar 06, 2011 at 07:22:45PM -0600, Anthony Liguori wrote:
>    
>> The Error class is similar to QError (now deprecated) except that it supports
>> propagation.  This allows for higher quality error handling.  It's losely
>> modeled after glib style GErrors.
>>      
> I know this offers more functionality than GError, but if we're going
> to be using GLib IMHO it would be very desirable to just use GError
> everywhere. Are the extra arbitary key,value pair fields really a
> compelling enough addition to make us not use GError ? libvirt started
> off with a very flexible error object that allowed extra string&  int
> values to be passed with each error, but after 5 years dev there is
> not a single place in our code where we use this. Simple error code
> and formatted strings have been sufficient, much like GError would
> allow.
>    

I wrote Error without even thinking of using GError.  My motivation was 
to move us off of QError.

We would lose key/value pairs which are actually quite useful.  Consider 
executing the qmp_cont() command after starting a guest with -S.  Right 
now, we'll throw a DeviceEncrypted error message that contains the drive 
name and encrypted filename which means a management app can immediately 
prompt the user for a password and then execute block_passwd.

Without key/value pairs, a management tool would need another round trip 
to do an info block and find out which devices are encrypted before 
doing the prompt.

I need to think a bit more about it.

Regards,

Anthony Liguori

> Regards,
> Daniel
>