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What messaging scenarios are supported by AMQP and RabbitMQ?

AMQP is a very general system that can be configured to cover a great variety of messaging middleware use-cases. For example:

• Point-to-point communication

  One of the simplest and most common scenarios is for a message producer to transmit a message addressed to a particular message consumer. AMQP covers this scenario by allowing queues to be named and to be bound to a "direct" exchange, which routes messages to queues by name.

• One-to-many broadcasting (including multicast)

  In this scenario, the broadcasters publish messages to an AMQP "fanout" exchange, and subscribers create and subscribe to their own private AMQP queues, which forward published messages on to them, with one copy per queue.

  Multicast is addressed at the broker implementation level. AMQP clients need not be made aware of transport-level optimisations such as multicast: broker clusters are free to use whatever such low-level optimisations are available from configuration to configuration.

  Multiple optimisations are possible, since AMQP separates routing logic (exchanges and bindings) from message queueing (queues). Multicast relates only to routing from message publishers to message queues, and as a routing optimisation can be completely physically decoupled from AMQP's logical semantics. Further optimisations include physical separation of exchange from queue or even colocation of queue with a consumer application.

• Transactional publication and acknowledgement

  AMQP supports transactional publication, where an AMQP channel is opened, transactional mode is selected, messages are published and acknowledged, and the transaction is committed. The system guarantees atomicity and durability properties for transactional message activity.

• High-speed transient message flows

  Messages are individually flagged as transient or persistent in AMQP at the time of publication. By sending messages outside the transactional part of the protocol, in non-persistent mode, an application can achieve very high throughput and low latency.

• Reliable persistent message delivery

  Messages that are published in persistent mode are logged to disk for durability. If the server is restarted, the system ensures that received persistent messages are not lost. The transactional part of the protocol provides the final piece of the puzzle, by allowing the server to communicate its definite receipt of a set of published messages.

• Store-and-forward

  Store-and-forward is implemented by delivering messages marked as "persistent" to AMQP's durable queues. Published, persistent messages delivered to durable queues are stored on disk until a consumer retrieves and deletes them.

• Wide area messaging

  Because routing logic is decoupled from message delivery, RabbitMQ is able to support extended broker clustering across WANs. Some of the approaches include AJAX-style access to AMQP resources, and spanning-tree pseudo-multicast implemented internally to a RabbitMQ cluster.

• File streaming

  The AMQP protocol, version 0-8, supports file streaming by way of the de>filede> content class. Very large files are transferred to a temporary area on the broker before being routed to queues for download by consumers.