[rabbitmq-discuss] Publish messages only when needed ?

Matthias Radestock matthias at rabbitmq.com
Fri Oct 8 10:18:56 BST 2010


Romain Conseil wrote:
> as you will see in the previous message, I tested the two settings for 
> exchanges (with x-lvc / with direct) : the difference is only 10% oc CPU 
> load and is still at 120% with direct exchanges.

Missed that, sorry. And thinking about it, 120% CPU for a 10kHz 
publisher stream sounds about right - I get similar figures on my machine.

> the problem is to have a routeIds list uptodate which requires :
> - to know the all list of bindings at pblisher startup
> - to be notify of each new binding when running.
> Would this be possible ?

You could write a custom exchange type that captures the bind/unbind 
events. It would maintain internal state (in mnesia, perhaps) to count 
the number of bindings per routeId. Whenever that count transitions 
between zero and non-zero it would publish an message to an exchange, 
with the routeId as the routing key.

Producers could then bind to that exchange to receive a stream of 
bind/unbind events relevant to them. And making that exchange an lvc 
exchange allows new producers to learn about the current state.



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