Book Image

Extending Puppet - Second Edition

By : Alessandro Franceschi, Jaime Soriano Pastor
Book Image

Extending Puppet - Second Edition

By: Alessandro Franceschi, Jaime Soriano Pastor

Overview of this book

Puppet has changed the way we manage our systems, but Puppet itself is changing and evolving, and so are the ways we are using it. To tackle our IT infrastructure challenges and avoid common errors when designing our architectures, an up-to-date, practical, and focused view of the current and future Puppet evolution is what we need. With Puppet, you define the state of your IT infrastructure, and it automatically enforces the desired state. This book will be your guide to designing and deploying your Puppet architecture. It will help you utilize Puppet to manage your IT infrastructure. Get to grips with Hiera and learn how to install and configure it, before learning best practices for writing reusable and maintainable code. You will also be able to explore the latest features of Puppet 4, before executing, testing, and deploying Puppet across your systems. As you progress, Extending Puppet takes you through higher abstraction modules, along with tips for effective code workflow management. Finally, you will learn how to develop plugins for Puppet - as well as some useful techniques that can help you to avoid common errors and overcome everyday challenges.
Table of Contents (19 chapters)
Extending Puppet Second Edition
About the Authors
About the Reviewer

Chapter 3. Introducing PuppetDB

A model based on agents that receive and apply a catalog received from the Puppet Master has an intrinsic limitation: the client has no visibility and direct awareness about the state of resources of the other nodes.

It is not possible, for example, to execute during the catalog application functions that do different things according to different external conditions. There are many cases where information about other nodes and services could be useful to manage local configurations, for example, we might:

  • Need to start a service only when we are sure that the database, the queues, or any external resource it relies upon are already available in some external nodes

  • Configure a load balancer that dynamically adds new servers, if they exist

  • Have to manage the setup of a cluster which involves specific sequences of commands to be executed in a certain order on different nodes

The declarative nature of Puppet's DSL might look inappropriate to manage setups or operations...