Message broker vs. MOM (Message-Oriented Middleware)

Question

I\'m a little confused as to what the difference is between a message broker e.g. RabbitMQ and Message-orientated Middleware. I can\'t find much info apart from what\'s on Wikip

Answer 1

"MOM" broadly means any technology that can deliver "messages" from one user-space application to another. A message is usually understood to be a discrete piece of information, as compared to a stream.

MOM products used to be quite large and complex: CORBA, JMS, TIBCO, WebsphereMQ, etc. and tried to do a lot more than simply deliver messages.

A broker is a particular set of routing and queuing patterns, and we usually use the term "broker" specifically in MOM (as compared to HTTP, email, XMPP, etc.) Routing means, one message goes to one peer, to one of many peers, to all of many peers, etc. Queuing means messages are held in memory or disk until they can be delivered (and in some cases, acknowledged).

AMQP used to specific those broker patters, so an application could rely on consistent behavior from any AMQP-compatible broker (thus RabbitMQ and OpenAMQ looked much the same to a client app, like two HTTP or two XMPP servers would look the same). AMQP/1.0 specifies just the connection between nodes, so you don't have guarantees of behavior. This makes AMQP/1.0 much easier for firms to implement, but doesn't deliver interoperability.

ZeroMQ is message-oriented middleware that defines, like AMQP/1.0, the connections between pieces rather than the behaviour of a central broker. However it's relatively easy to write MOM brokers using 0MQ, and we've done a few of these (like Majordomo).