[rabbitmq-discuss] Shovel Plugin For HA

Simon MacMullen simon at rabbitmq.com
Thu Oct 20 17:26:23 BST 2011

On 20/10/11 15:24, James Carr wrote:
> Thanks, I tried it and it works advertised, but I feel like I may have
> misunderstood it.

Just to be clear, we are still talking about the federation exchange, right?

> I've set it up and have messages published to a local exchange being
> routed to an exchange on a central broker. however when the central
> broker is down there's no local queuing of messages until it comes
> back up.

That should really be happening. I am assuming your local exchange is 
the upstream and the central exchange is the downstream. When the 
downstream connects to the upstream it should create a queue (with a 
name beginning "federation: " on the upstream. Can you see this in mgmt 
/ rabbitmqctl? Of course, if you use the queue_expires parameter the 
upstream queue will expire eventually.

> Of course, maybe I am just designing my topology wrong. Maybe instead
> of separate exchanges per application I should just have one exchange,
> shoveled out to the remote exchange and then multiple queues bound to
> that exchange. The exchange per app was going to make things
> heavyweight with the shovel plugin since I'd have to restart local
> brokers for each new exchange, but with a single exchange, single
> local queue and multiple remote queues might make things more
> effecient.
> Maybe the federation plugin includes a backing queue that can be
> switched on or am I  missing something?

It is always on - even if the downstream does not disconnect then the 
upstream might publish messages faster than they can get sent across the 

Cheers, Simon

Simon MacMullen
RabbitMQ, VMware

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