RabbitMQ Internals
This project aims to explain how RabbitMQ works internally. The goal is to make it easier to contribute for newcomers to the project, and at the same time have a common repository of knowledge to be shared across the project contributors.
Purpose
Most interesting modules in RabbitMQ projects have documentation essays, sometimes quite extensive, at the top. The aim here is not to duplicate what’s there, but to provide the highest-level overview as to the overall architecture.
Guides
In order to understand how RabbitMQ’s internals work, it’s better to try to follow the logic of how a message progresses through RabbitMQ as it is handled by the broker, otherwise, you would end up navigating through many guides without a clear context of what’s going on, or without knowing what to read next. Therefore we have prepared the following guides to help you understand how RabbitMQ works:
Basic Publish Guide
Here we follow the life of a message since it’s received from the network until it has been routed by the exchanges. We take a look at the various processing steps that happen to a message right until it is delivered to one or perhaps many queues.
Deliver To Queues Guide
After the message has been routed, the broker needs to deliver that message to the respective queues. Here not only the message has to be sent to queues, but also mandatory messages and publisher confirms need to be taken into account. Also, the queue needs to try to deliver the message to prospective consumer, otherwise the message ends up queued.
Queues and Message Store
Provides an overview of the Erlang processes that back queues and how they interact with the message store, message index and so on.
Variable Queue Guide
Ultimately, messages end up queued at the backing queue. From here they can be retrieved, acked, purged, and so on. The most common implementation of the backing queue behaviour is the rabbit_variable_queue module, explained in the following guide:
Mandatory Messages and Publisher Confirm Guides
As explained on the Deliver To Queues guide, a channel has to handle messages published as mandatory and also take care of publisher confirms. These processes are explained in the following guides:
Authentication and Authorization
As explained in the Basic Publish, there are some rules to see if a message can be accepted by the broker from a certain publisher. This is explained in the following guide:
Authorization and Authentication Backends
Internal Event Subsystem
In some cases components in a running node communicate via events. Some events are consumed by other nodes.
Management Plugin
An architectural overview of the v3.6.7+ version of the management plugin.
Maturity and Completeness
These guides are not complete, haven’t been edited, and are work in progress in general.
So if you find yourself wanting more detail, check the code first!
License
(c) Pivotal Software Inc, 2015-2016
Released under the Creative Commons Attribution-ShareAlike 3.0 Unported license.