[openstack-dev] [all] how to send messages (and events) to our users

Ryan Brown rybrown at redhat.com
Fri Apr 10 18:27:43 UTC 2015

On 04/10/2015 01:45 PM, Clint Byrum wrote:
> Excerpts from Ryan Brown's message of 2015-04-10 07:00:27 -0700:
>> On 04/09/2015 09:40 PM, Angus Salkeld wrote:
>>> ... [snip] ...
>>> Could Zaqar fulfil all of these use case? - Maybe.
>> Zaqar as it presently exists, maybe. Zaqar *wants* to fit these cases,
>> and they want our feedback if they are missing anything to support these.
>> The biggest stretch here IMO is (4) because not all Zaqar storage
>> backends support strict ordering, but that can be fixed at the
>> application layer.
> I'd recommend strongly to avoid requiring FIFO. It's a performance
> killer. Best effort is fine, and let the user sort through them by
> timestamp if they pop out in an odd order.

That's more or less what I meant by "fixed at the application layer"
since the frontend (in Horizon's case) or client (for CLI/external
progs) could do the "oh, 13:43T+00Z is before 13:45T+00Z" arithmetic
pretty simply. I was just noting that FIFO isn't free in all Zaqar

> So to summarize, I think this would make sense as a plan to get this
> into a usable state for all services to be able to offer:
> * Create a micro-service whose sole purpose in life is to filter
>   notifications. A user would interact with this service by submitting
>   requests for subscriptions, something like this:
>   POST https://service/subscription
>   {
>    "service": "compute",
>    "topic": {"server": {"id": "uuid-of-server"}}
>    "destination": "zaqar:https://zaqar/url/for/sending"
>   }
>   ... and all the other lovely restful things
> * Ensure notifications exist for user-interesting things and that they
>   don't overload ceilometer and the like with unnecessary notifications.
> If Zaqar becomes the piece that prevents adoption, add more destination
> drivers, such as atom feeds, logstash, AMQP queues, or syslog services.
> Horizon people, can you comment on whether this would be helpful for you
> too? It seems like it would!

Ryan Brown / Software Engineer, Openstack / Red Hat, Inc.

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