Let us consider the scenario below.
There are 3 RabbitMQ brokers(B1,B2,B3) deployed in a clustered model. There is an exchange E with bindings which is replicated to all the 3 brokers. There is a producer P and 3 consumers C1,C2,C3. I have the following questions
Lets say a producer connects to broker B1 and creates a Queue Q which is mirrored to B2. Now when a consumer connects to Broker B3, how does it get the messages in the queue?
From my understanding, the exchange and binding information is maintained in memory in each broker. If the exchange is persistent, in order to recover from broker crashes, is the exchange and binding information also persisted in the disk in all brokers?
If the entire queue is maintained in memory in all the mirrored brokers, it consumes a lot of memory in the broker. In order to support potentially large number of queues each holding millions of messages in each broker, is it not a constraint for scalability?
Each mirrored queue has a master node. The master node for that queue is always used for consuming. So when a consumer connects to a node which is does not have the queue storage (or is a slave node), the consumer will actually end up consuming from the master node.
Yes, assuming the node is a disc node and not a RAM node. I'm not 100% sure about the binding, but my guess is yes. Anyway, it's highly recommended to always declare all queues, exchanges etc that your client needs! (do this each time client starts or something)
Yes, that's the point of mirroring: add redundancy in case something goes wrong. It does not increase performance (rather the opposite!). But in general, queues with millions of messages is not exactly a good situation as queues should, on average, be empty