Hi folks,
I'd like to discuss a topic which was briefly touched on Aeolus
developer Conference in Brno. Many components of Aeolus project need to
send notifications to other components:
Heat -> Conductor (deployment/instance state changes)
Conductor -> Winged Monkey (deployment/instance state changes)
Imagefactory -> Conductor (notifications about image build&upload state)
DC tracker* -> Heat (notifications about instance state changes)
DC tracker -> Conductor (notifications about other provider resource
changes, realms availability, hw profile changes)
* DC Tracker - this component is actually not agreed yet, it was just a
proposal some time ago, but I believe this will be needed.
As far as I know there is no a unified plan how to deal with
notifications between components. At this point notifications are
implemented only in Imagefactory. This implementation is for now quite
simple - a notification callback is sent back as http PUT request. It
doesn't cover any failure situations (network error, auth error,
Conductor is not running...), so if a request is not successful, no
retry is done.
I think we need more robust notification system between all components
above, this system should support at least:
1) retry on failure
2) keep correct order of notifications
3) support authentication
And here it comes...
Why not use a message bus (an AMQP implementation) for communication
between all involved components?
- it supports all required features out of the box
- clients exists for all languages involved in Aeolus project
- notifications will be solved in the same way between all components
Or is there some other solution how to solve notifications as painless
as possible while keeping required robustness? What is your preferred
solution of this problem?
Jan
