Yesterday, we had a great conversation with Matt Rutkowski from IBM, one
of the authors of the CADF spec.

I was having a disconnect on what CADF offers and got it clarified.

My assumption was CADF was a set of transformation/extraction rules for
taking data from existing data structures and defining them as
well-known things. For example, CADF needs to know "who sent this
notification". I thought CADF would give us a means to point at an
existing data structure and say "that's where you find it".

But I was wrong. CADF is a full-on schema/data structure of its own. It
would be a fork-lift replacement for our existing notifications.
However, if your service hasn't really adopted notifications yet (green
field) or you can handle a fork-lift replacement, CADF is a good option.
There are a few gotcha's though. If you have required data that is
outside of the CADF spec, it would need to go in the "attachment"
section of the notification and that still needs a separate schema to
define it. Matt's team is very receptive to extending the spec to
include these special cases though.

Anyway, I've written up all the options (as I see them) [1] with the
advantages/disadvantages of each approach. It's just a strawman, so

Look forward to feedback!


On 9/3/2014 12:30 PM, Sandy Walsh wrote:
> On 9/3/2014 11:32 AM, Chris Dent wrote:
>> On Wed, 3 Sep 2014, Sandy Walsh wrote:
>>> We're chatting with IBM about CADF and getting down to specifics on
>>> their applicability to notifications. Once I get StackTach.v3 into
>>> production I'm keen to get started on revisiting the notification
>>> format and olso.messaging support for notifications.
>>> Perhaps a hangout for those keenly interested in doing something about this?
>> That seems like a good idea. I'd like to be a part of that.
>> Unfortunately I won't be at summit but would like to contribute what
>> I can before and after.
>> I took some notes on this a few weeks ago and extracted what seemed
>> to be the two main threads or ideas the were revealed by the
>> conversation that happened in this thread:
>>      * At the micro level have versioned schema for notifications such that
>>        one end can declare "I am sending version X of notification
>>" and the other end can effectively deal.
> Yes, that's table-stakes I think. Putting structure around the payload
> section.
> Beyond type and version we should be able to attach meta information
> like public/private visibility and perhaps hints for external mapping
> (this trait -> that trait in CADF, for example).
>>      * At the macro level standardize a packaging or envelope of all
>>        notifications so that they can be consumed by very similar code.
>>        That is: constrain the notifications in some way so we can also
>>        constrain the consumer code.
> That's the intention of what we have now. The top level traits are
> standard, the payload is open. We really only require: message_id,
> timestamp and event_type. For auditing we need to cover Who, What, When,
> Where, Why, OnWhat, OnWhere, FromWhere.
>>      These ideas serve two different purposes: One is to ensure that
>>      existing notification use cases are satisfied with robustness and
>>      provide a contract between two endpoints. The other is to allow a
>>      fecund notification environment that allows and enables many
>>      participants.
> Good goals. When Producer and Consumer know what to expect, things are
> good ... "I know to find the Instance ID <here>". When the consumer
> wants to deal with a notification as a generic object, things get tricky
> ("find the instance ID in the payload", "What is the image type?", "Is
> this an error notification?")
> Basically, how do we define the principle artifacts for each service and
> grant the consumer easy/consistent access to them? (like the 7-W's above)
> I'd really like to find a way to solve that problem.
>> Is that a good summary? What did I leave out or get wrong?
> Great start! Let's keep it simple and do-able.
> We should also review the oslo.messaging notification api ... I've got
> some concerns we've lost our way there.
> -S
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