Competing Consumers from load balancing application in MassTransit/RabbitMQ

Question

I have just finished creating an API where the requests from the API are forwarded to a back-end service via MassTransit/RabbitMQ using the Request/Response pattern. We are now looking at pushing this into production, and are wanting to have multiple instances of the application (both API and service) running on different services, with a load balancer distributing the requests between them.

This leaves us in a position where we could potentially lose all of the messages if one of the servers is taken out of the pool for any reason. I am looking at creating a RabbitMQ cluster between the servers (each server has a local install) and was wondering how I would go about setting up the competing consumers in this instance.

Does RabbitMQ or MassTransit handle this so that only one consumer will receive the request, or will all consumers receive it and attempt to respond? Also, with the RabbitMQ cluster, how will MassTransit/RabbitMQ handle a node failing?

Answer 1

You should take a look at this document. http://www.rabbitmq.com/distributed.html

Explains the common distributed scenarios quite nicely. For your scenario I think federation would be a better fit than clustering. If you go for clustering you should look at mirrored queues.

If all you need is performance you are better of getting a single server to handle your message queuing and the other server will connect to it and produce/consume messages.

I don't know how Mass Transit works but, if Request/Response is used you should get a single delivery of message to a single consumer, if the message is not ack-ed (the consumer crashes) an other consumer should pick it up.