Book Image

Extending SaltStack

Book Image

Extending SaltStack

Overview of this book

Salt already ships with a very powerful set of tools, but that doesn't mean that they all suit your needs perfectly. By adding your own modules and enhancing existing ones, you can bring the functionality that you need to increase your productivity. Extending SaltStack follows a tutorial-based approach to explain different types of modules, from fundamentals to complete and full-functioning modules. Starting with the Loader system that drives Salt, this book will guide you through the most common types of modules. First you will learn how to write execution modules. Then you will extend the configuration using the grain, pillar, and SDB modules. Next up will be state modules and then the renderers that can be used with them. This will be followed with returner and output modules, which increase your options to manage return data. After that, there will be modules for external file servers, clouds, beacons, and finally external authentication and wheel modules to manage the master. With this guide in hand, you will be prepared to create, troubleshoot, and manage the most common types of Salt modules and take your infrastructure to new heights!
Table of Contents (21 chapters)
Extending SaltStack
Credits
Foreword
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Returning data to the master


Salt's architecture is based on the publish-subscribe pattern, known colloquially as pub/sub. In this design, one or more clients subscribe to a message queue. When a message is published to the queue, any current subscribers receive a copy, which they usually process in some way.

Salt in fact makes use of two message queues, both of which are managed by the Master. The first is used by the Master to publish commands to its Minions. Each Minion can see the messages published to this queue, but they will only react to them if the Minions are included in the target. A message targeted to '*' will be processed by all Minions that are connected, whereas one targeted to 192.168.0.0/16 using the -s command-line option will only be processed by Minions whose IP address starts with 192.168.

The second message queue is also hosted by the Master, but messages are published to it from Minions, and the Master itself is the subscriber. These messages are normally stored in...