RabbitmqHA
- Launchpad Entry: NovaSpec:tbd
- Created: 19 October 2010
- Last updated: 19 October 2010
- Contributors: Armando Migliaccio
Summary
This specification covers how Nova supports RabbitMQ configurations like clustering and active/passive replication.
Release Note
Austin release of Nova RPC mappings deals with intermittent network connectivity only. In order to support RabbitMQ clusters and active/passive brokers, more advanced Nova RPC mappings need to be provided, such as strategies to deal with failures of nodes holding queues within clusters and/or master/slave failover for active/passive replication.
Rationale
Currently, the message queue configuration variables are tied to RabbitMQ from nova/flags.py. In particular, only one rabbitmq host is provided and it is assumed, for simplicity of the deployment, that a single instance is up and running. In face of failures (e.g. disk or power related) of the RabbitMQ host, Nova components cannot send/receive messages from the queueing system until it recovers. To provide higher resiliency, RabbitMQ can be made to work in an active/passive setup, such that persistent messages that have been written to disk on the active node are able to be recovered by the passive node should the active node fail. If high-availability is required, active/passive HA can be achieved by using shared disk storage, heartbeat/pacemaker, and possibly a TCP load-balancer in front of the service replicas. Although this solution ensures the least amount of development effort on the client-side (e.g. Nova API, Scheduler, Compute, etc.) it still represents a bottleneck of the overall architecture and may require expensive hardware.
