[Other] RabbitMQ 4 / AMQP 1.0 : Broacasting with fanout/temporary queue

[gcuisinier]

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RabbitMQ version used

4.0.3

How is RabbitMQ deployed?

Community Docker image

Steps to reproduce the behavior in question

Hello,

I am not sure that it's the best place to ask, so sorry if it's not :)

When acccessing with RabbitMQ in AMQ 0.9.1, I was able to implements a broadcasting of all message to all clients "connected" to an exchange.
For that, with Quarkus RabbitMQ, I configured a temporary queue ( server side generated name) to be created and bound to an existing fanout exchange, for each client connected ( ex : multiple instance of an application pod ).

And now I am trying to reproduce this in AMQP 1.0.0.
But as there is a no Exchange/Queue in the protocol itself, according what I understood, every object should be created in RabbitMQ before, and accessed with an address ( ex : /exchanges/my-exchange or /queues/my-queue).
So I am still able to create an fanount exchange in Rabbit, and send message to it.

But it seems not possible to create temporary queue on the fly and bound them to the exchange in AQMP 1.0.0.
Am i right ? it is something not implemented yet ? Or something that will never come in futur ?

[michaelklishin]

Exchanges do not exist as a concept in AMQP 1.0. However, /exchange/{name} can be used to publish to amq.fanout even then, and definitions can be used to declare any topology, even if an AMQP 1.0 client you use does not offer an obvious way of setting it up.

[gcuisinier]

Thank you for your quick replies :)

@michaelklishin Yes I was able already to send to pre-declared fanout exchange, with a set of "static" queue bound on it.

But, in AMQP 0.9.1 (abstracted by Quarkus/SmalRye messaging), I was able to declare a queue (server-named queue) that will be created by the server on on connection (and deleted automatically when the client disconnect), and bound it to the exchange dynamically

Doc : https://www.rabbitmq.com/docs/queues#server-named-queues

In quarkus it was "abstracted" behing. this config
mp.messaging.incoming.sse-channel-in.queue.name=(server.auto) mp.messaging.incoming.sse-channel-in.queue.declare=true mp.messaging.incoming.sse-channel-in.queue.exclusive=true mp.messaging.incoming.sse-channel-in.auto-bind=true

So if I well understood your answer @mkuratczyk mkuratczyk, this management extension shoud allow creating this kind of temporary server-named queue too (that will also be removed automatically on client disconnection) ?
And also bound them to the exchange?

[mkuratczyk]

Yes, you can declare exclusive queues this way. Once declared, they are just exclusive queues like any other in RabbitMQ, so they will be deleted when the connection closes.

[gcuisinier]

And does it also support server generated name ? Or should the unicity of name be managed on application side ?

[ansd]

But it seems not possible to create temporary queue on the fly and bound them to the exchange in AQMP 1.0.0. Am i right ?

No, it's possible with the RabbitMQ AMQP 1.0 client libs. You can create any exchanges/queues/bindings you want.

And does it also support server generated name ? Or should the unicity of name be managed on application side ?

It's easiest if your client creates a unique name. (For example you could take the container-id and link-name and some random number or timestamp).

Alternatively, RabbitMQ 4.1 adds server named queues via the dynamic field. See #13231

rabbitmq-server/deps/rabbit/test/amqp_client_SUITE.erl

Lines 4885 to 4908 in b8244f7

	%% "The address of the source MUST NOT be set" [3.5.3]
	Source = #{address => undefined,
	dynamic => true,
	capabilities => [<<"temporary-queue">>],
	durable => none},
	AttachArgs = #{name => <<"rpc-client-receiver🥕"/utf8>>,
	role => {receiver, Source, self()},
	snd_settle_mode => unsettled,
	rcv_settle_mode => first,
	filter => #{}},
	{ok, ReceiverClient} = amqp10_client:attach_link(SessionClient, AttachArgs),
	RespAddr = receive {amqp10_event, {link, ReceiverClient, {attached, Attach}}} ->
	#'v1_0.attach'{
	source = #'v1_0.source'{
	address = {utf8, Address},
	dynamic = true}} = Attach,
	Address
	after 30000 -> ct:fail({missing_event, ?LINE})
	end,
	%% The client doesn't really care what the address looks like.
	%% However let's do whitebox testing here and check the address format.
	%% We expect the address to contain both container ID and link name since they are short.
	?assertMatch(<<"/queues/amq.dyn-rpc-client-rpc-client-receiver", _CarrotAndGUID/binary>>,
	RespAddr),

shows an example of how a RabbitMQ agnostic AMQP 1.0 client can create exclusive server named queues dynamically.

[Gsantomaggio]

@gcuisinier This example may help. It is in Go but you can do the same with .net, java and python,.

[acogoluegnes]

The management extension does not support server-named queues. Our client libraries generate a random name when the user does not provide any. This applies to all types of queues (exclusive or not).

RabbitMQ 4.1 (not released yet) supports the AMQP 1.0 dynamic field when declaring a sender or a receiver. The effect is the same as declaring a server-named exclusive queue (as mentioned in @ansd's answer). Here is an example with QPid ProtonJ2 (the library the RabbitMQ AMQP 1.0 Java client uses). The queue is never explicitly created. Note the receiver.address() call to get the address of the queue when creating the sender.

[gcuisinier]

Thank you for all those informations :)