[rabbitmq-discuss] Queue inspector.

Thu Nov 8 08:42:28 GMT 2007

On 8 Nov 2007, at 07:30, Brian Granger wrote:
> This question definitely makes sense.  In our system some types of
> messages can only be consumed by particular workers.  These message
> bypass any load balancing.  For these types of messages the producers
> do need to be able to do things like 1) discover which consumers are
> currently available 2) send messages to specific consumers and 3) get
> back results from those consumers.

If certain types of messages have to be processed by particular  
consumers, this could be achieved by having consumers bind to  
different queues, I think. It also sounds like a use case for using  
predicates in header based routing, which unfortunately is not  
currently implemented in rabbit.

Point 3 sounds like asynchronous RPC, for which there is already a  
pattern.

Points 1 and 2 sound like they are required to support point 3, but  
I'm still failing to see the concrete business requirement for that,  
but having said that, I don't understand your domain.

>> Hence I was asking whether it had
>> to be producer driven rather than consumer driven.
>
> It is definitely producer driven in the sense the the producer is the
> one making decisions about where to send what types of messages.

Thats why I was asking whether you can turn the decision on it's head  
by just having the producers fire and forget and letting the consumers  
dequeue messages based on some predicate.

>
> There is definitely conversational state between producers and
> particular consumers.  The consumer's also maintain a lot of internal
> state.  You could even look at our consumers as state machines that
> change state in response to the messages.

Fair enough. If you do need to maintain a conversation between a  
producer and consumer over multiple message exchanges then I can see  
why things might have to be determined by the producer.

Ben 
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