What is the "delivery mode" in AMQP?

Question

I understand that 2 options are available:

"Non-persistent"
"Persistent"

But what does this actually mean?

"Non-persistent" as in : the AMQP fabric will try to deliver the message if there are no consumers, the message will be dropped?

"Persistent" as in : AMQP will retry the message until a consumer accepts it??

score 73 · Accepted Answer · edited Jan 18 '19 at 18:48

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Messages marked as 'persistent' that are delivered to 'durable' queues will be logged to disk. Durable queues are recovered in the event of a crash, along with any persistent messages they stored prior to the crash.

edited Jan 18 '19 at 18:48

fgblomqvist

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answered Mar 01 '10 at 14:13

alexis

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I do not understand why you can declare an Exchange durable. And on the other side you "could"!? declare a queue that "corresponds" to that Exchange nondurable? Or for example if you would declare a Exchange NONDURABLE but a queue durable, and there would be a crash. Could I recover that durable queue in the nondurable exchange? @alexis – noBillSide Jun 27 '13 at 13:52
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"durability" only means the Exchange or Queue will survive a server restart.. This does not mean the messages being stored in a durable queue will survive... That would _also_ require a message level property `.deliveryMode = 2`. (I just tested these cases) – Myobis Jan 06 '14 at 09:04

score 23 · Answer 2 · edited Aug 24 '12 at 08:12

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delivery_mode in AMQP determines if message will be stored on disk after broker restarts. You can mark messages as persistent - by seting delivery_mode property = 2 when you publish message for instance in PHP (PECL AMQP extension):

$exchange->publish($text, $routingKey, null, array('delivery_mode' => 2));

You would also need to declare queue as durable (or it will be dropped after broker stops)

$queue->setFlags(AMQP_DURABLE);

edited Aug 24 '12 at 08:12

j0k

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answered Aug 23 '12 at 14:40

Greg Motyl

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Will the continue to be stored on disk even after they are processed? Or is it only a guarantee that they will be persisted until they get processed? – cs_pupil Jan 19 '23 at 17:47

score 0 · Answer 3 · answered Feb 21 '23 at 02:38

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The value of the delivery mode will tell RabbitMQ if it’s allowed to keep the message in memory when the message is placed in a queue (non-persistent) or if it must store the message on disk first (persistent).

answered Feb 21 '23 at 02:38

Chris Bao

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What is the "delivery mode" in AMQP?

3 Answers3

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