Protocol Extensions

Overview

The RabbitMQ implements a number of extensions of the AMQP 0-9-1 specification, which we document here.

Some extensions introduce new protocol methods (operations); others rely on existing extension points such as optional queue arguments.

Publishing

Publisher Confirms (aka Publisher Acknowledgements) are a lightweight way to know when RabbitMQ has taken responsibility for messages.
Blocked Connection Notifications allows clients to be notified when a connection is blocked and unblocked.

Consuming

Consumer Cancellation Notifications let a consumer know if it has been cancelled by the server.
basic.nack extends basic.reject to support rejecting multiple messages at once.
Consumer Priorities allow you to send messages to higher priority consumers first.
Direct reply-to allows RPC clients to receive replies to their queries without needing to declare a temporary queue.

Message Routing

Exchange to Exchange Bindings allow messages to pass through multiple exchanges for more flexible routing.
Alternate Exchanges route messages that were otherwise unroutable.
Sender-selected Distribution allows a publisher to decide where messages are routed directly.

Message Lifecycle

Per-Queue Message TTL determines how long an unconsumed message can live in a queue before it is automatically deleted.
Per-Message TTL determines the TTL on a per-message basis.
Queue TTL determines how long an unused queue can live before it is automatically deleted.
Dead Letter Exchanges ensure messages get re-routed when they are rejected or expire.
Queue Length Limit allows the maximum length of a queue to be set.
Priority Queues support the message priority field (in a slightly different way).

Authentication and Identity

The User-ID message property is validated by the server.
Clients that advertise the appropriate capability may receive explicit authentication failure notifications from the broker.
update-secret to be able to renew credentials for an active connection, when those credentials can expire.

AMQP 0-9-1 Spec Differences

Some features that were in AMQP 0-8 were deprecated in AMQP 0-9-1. We have undeprecated some of them and introduced a couple of tiny behaviour changes that improve usability of the product. Please refer to the spec differences page.

There's also an AMQP 0-9-1 Errata page which explains how various

Getting Help and Providing Feedback

If you have questions about the contents of this guide or any other topic related to RabbitMQ, don't hesitate to ask them on the RabbitMQ mailing list.

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