Cloned from launchpad blueprint https://blueprints.launchpad.net/ceilometer/+spec/replace-rpc-cast-with-notifications.

Description:

Ceilometer uses rpc.cast() calls internally to send sample data from the pipeline to the collector. We chose that route because we wanted to be able to scale the collector horizontally, and there was no way at the time to subscribe multiple consumers to notifications. Now that there is, we should switch to a notification format, to make it easier for third-party consumers of our sample data. The message payload shouldn't need to change substantially to make that work, and we can continue to publish the old RPC endpoint for now to make upgrades easier.

Specification URL (additional information):

None