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Hi,

On the PTG a question was raised that why don't we have the full 
traceback in the versioned error notifications as the legacy 
notifications has the full traceback.

I dig into the past and found out that this difference was intentional. 
During the original versioned notification spec review [2] there was 
couple of back and forth what to add to the ExceptionPayload and what 
not. I think the main reasons not to add the full traceback was that it 
cannot be well defined what goes in that field (it would have been a 
single serialized string) and possible security implications. Then in 
the review we ended up agreing on the ExceptionPayload structure [3] 
that was later implemented and merged.

The instance-action REST API has already provide the traceback to the 
user (to the admin by default) and the notifications are also admin 
only things as they are emitted to the message bus by default. So I 
assume that security is not a bigger concern for the notification than 
for the REST API. So I think the only issue we have to accept is that 
the traceback object in the ExceptionPayload will not be a well defined 
field but a simple string containing a serialized traceback.

If there is no objection then Kevin or I can file a specless bp to 
extend the ExceptionPayload.

Cheers,
gibi

[1] L387 in https://etherpad.openstack.org/p/nova-ptg-rocky
[2] https://review.openstack.org/#/c/286675/
[3] 
https://review.openstack.org/#/c/286675/12/specs/newton/approved/versioned-notification-transformation.rst@405