The oslo.messaging library supports the concept of service-specific transports (e.g. backends) to allow RPC and Notification services to employ different messaging technologies. The need for this dual messaging backend capability is driven by the limitations of broker-based messaging for RPC communications with regard to complexity, scalability and resiliency. The temporal coupling of OpenStack service RPC communications favors a brokerless message bus based on direct messaging capabilities rather than queuing. Meanwhile, the operation of Notification services remain best served by a broker based "store and forward" messaging bus.
This presentation will review the oslo.messaging RPC and Notification services and the operation of brokerless and broker-based messaging backends. The steps to configure and operate dual messaging backends will be demonstrated. An explanation of how high availability and cloud distribution can be realized will be provided.
Attendees will learn about the the concept of oslo.messaging RPC and Notification communications services. They will understand the temporal requirements of RPC communications and the constraints that queues place on this communication pattern. Attendees will learn about the use of the apache qpid-dispatch-router for a direct messaging backend for RPC. They will learn about the operational considerations for deploying dual messaging backends in OpenStack and the upstream activities for installation and configuration.