In RabbitMQ, messages are not published directly to a queue. Instead, the producer sends messages to an exchange. Use this tag only if your question is about the RabbitMQ Exchanges, or if the question revolves around the routing keys or message queues to which the exchange delivers the message for end publishing.
RabbitMQ is a message broker based on the AMPQ protocol.
Exchanges are AMQP entities where messages are sent. Exchanges take a message and route it into zero or more queues. The routing algorithm used depends on the exchange type and rules called bindings. AMQP 0-9-1 brokers provide four exchange types:
- Direct exchange:
(empty string)and amq.direct - Fanout exchange:
amq.fanout - Topic exchange:
amq.topic - Headers exchange:
amq.match(andamq.headersin RabbitMQ)
Besides the exchange type, exchanges are declared with a number of attributes, the most important of which are:
- Name
- Durability (exchanges survive broker restart)
- Auto-delete (exchange is deleted when all queues have finished using it)
- Arguments (these are broker-dependent)
Exchanges can be durable or transient. Durable exchanges survive broker restart, whereas transient exchanges do not (they have to be redeclared when the broker comes back online). Not all scenarios and use cases require exchanges to be durable.
RabbitMQ is open source message broker software (sometimes called message-oriented middleware) that implements the Advanced Message Queuing Protocol (AMQP). The RabbitMQ server is written in the Erlang programming language and is built on the Open Telecom Platform framework for clustering and failover. Client libraries to interface with the broker are available for all major programming languages.
