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< RabbitMQ mailing list ~ [Q] fanout exchange same as direct with blank routing key? |
| Guest |
 Posted: Wed Dec 09, 2009 12:14 pm |
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Guest
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On Thu, Dec 03, 2009 at 01:01:50PM -0600, Chuck Remes wrote:
> My question is in the subject.
The answer is no. 
They are the same only if every binding to the direct exchange uses an
empty binding key, and, as you say, all the publishes are with a
blank routing key.
In many ways, you can think of a direct exchange as a cluster of fanout
exchanges where there is implicitly a fanout for every routing key and
binding key.
> The only difference I can
> think of would be that there might be some matching done against the
> empty string routing key for delivery through the direct exchange that
> is skipped for the fanout exchange. Therefore, a fanout exchange would
> have *slightly* better performance versus a direct exchange with an
> empty routing key.
Correct, and the greater the number of different binding keys the direct
exchange has, the slower it will be. So if performance is important to
you, and you can get away with using a fanout, do so.
Matthew
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| tonyg |
| Posted: Fri Dec 18, 2009 12:07 pm |
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Joined: 07 Nov 2006
Posts: 199
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Matthew Sackman wrote:
> Correct, and the greater the number of different binding keys the direct
> exchange has, the slower it will be. So if performance is important to
> you, and you can get away with using a fanout, do so.
Hmm, this shouldn't be the case; fanout exchanges query the binding
table with a pattern of (name=ExchangeName, key=_), whereas direct
exchanges query it with (name=ExchangeName, key=RoutingKey). The
internal mnesia logic and indexing should be almost identical, as should
the performance; hmm, I'll see if I can measure it this afternoon.
Tony
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