[rabbitmq-discuss] Simultaneous Scalability and HA

[Matthias Radestock]

On 21/06/13 11:17, Tim Watson wrote:
> Mirroring / HA provides replication of contents for 1 queue, that
> you've chosen to mirror, and *you can maintain the queue's state
> across however many replicas you see fit*

That is the crucial bit.

If you want HA *and* increased scalability then create a cluster with >2 
nodes and configure your HA policy to mirror queues across a subset of them.

The 'exactly' and 'nodes' policies allow you to do that. See 
http://www.rabbitmq.com/ha.html#genesis.

NB: RabbitMQ in Action predates the introduction of server-configured 
policies; the x-ha-policy queue parameter does nothing in modern 
rabbits. See the above docs for the new way of configuring HA.

Regards,

Matthias.