RabbitMQ

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Notes for RabbitMQ.

RabbitMQ for beginners

Rabbit is a message-queueing software called a massage broker.

RabbitMQ example

Example: Users upload information to a website, and site will handle this information and generate a PDF and email it back to the user.

fig. 1

  1. The user sends a PDF creation request to the web application.
  2. The web application (the producer) sends a message to RabbitMQ, including data from the request, like name and email.
  3. An exchange accepts the messages from a producer application and routes them to correct message queues for PDF creation.
  4. The PDF processing worker (the consumer) receives the task and starts the processing of the PDF.

fig. 2 An exchange is responsible for the routing of the messages to the different queues.

Exchanges

There are different types of exchanges: Direct, Topic and Fanout. fig. 3

  • Direct: A direct exchange delivers messages to queues based on a massage routing key.
  • Topic: The topic exchange does a wildcard match between the routing key and the routing pattern specified in the binding.
  • Fanout: A fanout exchange routes messages to all of the queues that are bound to it.

Server concepts

  • Producer: application that sends the messages.
  • Consumer: application that receives the messages.
  • Queue: buffer that store messages.
  • Exchange: receives messages from producers and pushes them to queues depending on rules defined by the exchange type. To receive messages, a queue needs to be bound to at least one exchange.
  • Binding: is a link between a queue and an exchange.
  • Routing Key: is a key that the exchange looks at to decide how to route the message to queues. The routing key is like an address for the message.