Is RabbitMQ capable of "pushing" messages from a queue to a consumer?

Question

With RabbitMQ, is there a way to "push" messages from a queue TO a consumer as opposed to having a consumer "poll and pull" messages FROM a queue?

This has been the cause of some debate on a current project i'm on. The argument from one side is that having consumers (i.e. a windows service) "poll" a queue until a new message arrives is somewhat inefficient and less desirable than the idea having the message "pushed" automatically from the queue to the subscriber(s)/consumer(s).

I can only seem to find information supporting the idea of consumers "polling and pulling" messages off of a queue (e.g. using a windows service to poll the queue for new messages). There isn't much information on the idea of "pushing" messages to a consumer/subscriber...

Answer 1

Having the server push messages to the client is one of the two ways to get messages to the client, and the preferred way for most applications. This is known as consuming messages via a subscription.

The client is connected. (The AMQP/RabbitMQ/most messaging systems model is that the client is always connected - except for network interruptions, of course.)

You use the client API to arrange that your channel consume messages by supplying a callback method. Then whenever a message is available the server sends it to the client over the channel and the client application gets it via an asynchronous callback (typically one thread per channel). You can set the "prefetch count" on the channel which controls the amount of pipelining your client can do over that channel. (For further parallelism an application can have multiple channels running over one connection, which is a common design that serves various purposes.)

The alternative is for the client to poll for messages one at a time, over the channel, via a get method.