CODEWITHSUNDEEP
rabbitmq
GreenEyedAndy
GreenEyedAndy

Reputation: 1525

RabbitMQ same message to each consumer

I have implemented the example from the RabbitMQ website: RabbitMQ Example

I have expanded it to have an application with a button to send a message. Now I started two consumer on two different computers. When I send the message the first message is sent to computer1, then the second message is sent to computer2, the thrid to computer1 and so on.

Why is this, and how can I change the behavior to send each message to each consumer?

Upvotes: 11

Views: 24823

Answers (4)

noob7
noob7

Reputation: 1147

What youre doing is essentially 'worker queues' model which is used to distribute tasks among worker nodes. Since each task needs to be performed only once, the message is sent to only one node. If you want to send a message to all the nodes, you need a different model called 'pub-sub' where each message is broadcasted to all the subscribers. The following link shows a simple pub-sub tutorial https://www.rabbitmq.com/tutorials/tutorial-three-python.html

Upvotes: 1

Regular Joe
Regular Joe

Reputation: 1

I would see this more as a design question. Ideally, producers should create the exchanges and the consumers create the queues and each consumer can create its own queue and hook it up to an exchange. This makes sure every consumer gets its message with its private queue.

Upvotes: 0

Derick Bailey
Derick Bailey

Reputation: 72888

Why is this

As noted by Yazan, messages are consumed from a single queue in a round-robin manner. The behavior your are seeing is by design, making it easy to scale up the number of consumers for a given queue.

how can I change the behavior to send each message to each consumer?

To have each consumer receive the same message, you need to create a queue for each consumer and deliver the same message to each queue.

The easiest way to do this is to use a fanout exchange. This will send every message to every queue that is bound to the exchange, completely ignoring the routing key.

If you need more control over the routing, you can use a topic or direct exchange and manage the routing keys.

Whatever type of exchange you choose, though, you will need to have a queue per consumer and have each message routed to each queue.

Upvotes: 39

Yazan
Yazan

Reputation: 6082

you can't it's controlled by the server check Round-robin dispatching section

It decides which consumer turn is. i'm not sure if there is a set of algorithms you can pick from, but at the end server will control this (i think round robin algorithm is default)

unless you want to use routing keys and exchanges

Upvotes: 3

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