RabbitMQ exchange bind replicating messages published to one exchange across two other exchanges

Question

I have 3 different exchanges in my rabbitMQ i am trying to route all the messages sent to mainex across the other two exchanges dmyex and monex i tried to use the channel.exchngeBind method to bind the exchanges.

I am still not able to see the messages published to mainex going to dmyex and monex.

Is this possible in RabbitMq?

Is there any mistake in what i am doing here?

ch.exchangeDeclare("mainex", DIRECT_EXCHANGE_TYPE, true, false, null);
ch.exchangeDeclare("dmyex", CONSISTENT_HASH_EXCHANGE_TYPE, true, false, null);
ch.exchangeDeclare("monex", CONSISTENT_HASH_EXCHANGE_TYPE, true, false, null);
ch.exchangeBind("dmyex","mainex","abcd_KEY");
ch.exchangeBind("monex","mainex","abcd_KEY");

score 0 · Answer 1 · answered Jul 21 '20 at 12:36

I think that the exchange mainex will need to be a Topic exchange in order for wildcard routing to work, as Direct exchanges do their routing based on exact matching of the routing key. Per this CloudAMQP blog post on exchange types and routing:

A direct exchange delivers messages to queues based on a message routing key. The routing key is a message attribute added to the message header by the producer. Think of the routing key as an "address" that the exchange is using to decide how to route the message. A message goes to the queue(s) with the binding key that exactly matches the routing key of the message.

(This is also touched on in this answer to a question about wildcard routing keys on SO)

That should be enough to get your routing working. Perhaps even more simply, if you are going to match any routing key for all of your exchanges that are bound to mainex, you could just make mainex a Fanout exchange.

Thank you for your response greg, I tried this using the specific routing keys i am able see the messages in mainex exchange when i publish with "grid" routing key but these same messages are not going to dmyex and monex. — Rajesh Babu Devabhaktuni, Jul 21 '20 at 14:12
Yes i have a shard policy on the consistent hash exchanges dmyex and monex and have 2 shards per node on the cluster. — Rajesh Babu Devabhaktuni, Jul 22 '20 at 15:07

score 0 · Accepted Answer · answered Jul 23 '20 at 18:46

Just figured out the below model is working.

   ch.exchangeDeclare("mainex", DIRECT_EXCHANGE_TYPE, true, false, null);
   ch.exchangeDeclare("dmyex", CONSISTENT_HASH_EXCHANGE_TYPE, true, false, null);
   ch.exchangeDeclare("mongoex", CONSISTENT_HASH_EXCHANGE_TYPE, true, false, null);
   
   
   ch.exchangeBind("dmyex","mainex", "abcd_KEY");
   ch.exchangeBind("monex","mainex", "abcd_KEY");
   
   
   for (String q : Arrays.asList("sharding: dmyex - rabbit@node1 - 0", "sharding: dmyex - rabbit@node2 - 0","sharding: dmyex - rabbit@node3 - 0","sharding: dmyex - rabbit@node4 - 0","sharding: dmyex - rabbit@node5 - 0","sharding: dmyex - rabbit@node6 - 0")) {
       ch.queueBind(q, "dmyex", "1");
   }
   
   
   for (String q : Arrays.asList("sharding: mongoex - rabbit@node1 - 0", "sharding: mongoex - rabbit@node2 - 0","sharding: mongoex - rabbit@node3 - 0","sharding: mongoex - rabbit@node4- 0","sharding: mongoex - rabbit@node5 - 0","sharding: mongoex - rabbit@node6 - 0")) {
       ch.queueBind(q, "mongoex", "1");
   }
   
   
     AMQP.BasicProperties.Builder bldr = new AMQP.BasicProperties.Builder();
     for (int i = 0; i < 10; i++) {
     ch.basicPublish("mainex", "abcd_KEY", bldr.build(), "TestMessage".getBytes("UTF-8"));````

RabbitMQ exchange bind replicating messages published to one exchange across two other exchanges

2 Answers2