[ckan-dev] AMQP topic vs direct exchange

Mon Jan 10 17:36:27 UTC 2011

Hi all,

The queueing mechnism that I've used for, e.g. ORDF is to use
a fanout exchange which will not drop messages but also provides
no means for filtering at the AMQP level.

Direct exchanges will, I believe, round-robin amongst listeners
so you have to specify an exchange for each type of listener
a priori and repeat the messages for each on the sender side
(or daisy-chain with some direct exchanges listening to a fanout
exchange which is sort of pointless).

Cheers,
-w

* [2011-01-10 17:00:31 +0100] Friedrich Lindenberg <friedrich at pudo.org> écrit:

] Hi James,
] 
] On Mon, Jan 10, 2011 at 4:31 PM, James Gardner <james at 3aims.com> wrote:
] > I had a good look at AMQP over Christmas and from what I can tell,
] > workers can't consume a message from a topic queue unless they are
] > running at the time the message was sent. This would mean messages sent
] > to the queue could be lost even if durability settings were enabled.
] 
] This is true. I've had some problems in the past where a lot of items
] accumulated on the queue so I chose the topic queue partly for that
] reason.
] 
] The other reason is that it allows us to play with instance
] identifiers, i.e. someone could listen on #.ckan.net to get updates
] from all country instances (so you would only have to run the archiver
] once instead of per-instance). Since we don't do that at the moment,
] this could be removed, though. Either way, it should be a config
] setting.
] 
] What do the others think?
] 
] Best,
] 
]  Friedrich

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