[rabbitmq-discuss] Message Aggregating Queue

Alexis Richardson alexis at rabbitmq.com
Thu Apr 28 14:01:09 BST 2011


On Thu, Apr 28, 2011 at 1:54 PM, Jason Zaugg <jzaugg at gmail.com> wrote:
> Thanks for the great ideas and discussion so far!
> Another requirement I should make explicit: we have a single consumer
> reading the stream of price updates for all stocks; and it should
> process them the order. That is, we don't want to 'UBS' to move to the
> back of the queue if it updates before the previous message is
> processed. So a data structure like as LinkedHashMap would be needed
> for the custom queue proposed by Alvaro.

I'm confused.  Would this stream contain exactly one price per ticker
symbol?  If so then why does it have to be a stream and not a set?  If
it must be a stream with multiple values per ticker, then just use
direct exchanges and one queue for the full stream.

> The Last Value Caching Exchange seems to solve a slightly different
> problem (although one that we also have!). If I understand it, a queue
> attached to the LVC exchange would receive *every* newly delivered
> message, regardless of how fast it is able to process them.

Correct.  The LVC exchange is just a map from ticker to last value.
It does not affect delivery of subsequent messages.

Are you sure you wouldn't be better off using a cache?

> In
> addition, as soon as the queue is bound the the exchange, it would
> receive the last value for each routing key.



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