Mastering Ansible

Jesse Keating

• Publisher: Packt Publishing
• Year: 2015
• eBook ISBN: 9781784395483
• Edition: 1
• Topic: Computer Science
• Subtopic: Application Development
• Index: Computer Science

Design, develop, and solve real world automation and orchestration needs by unlocking the automation capabilities of Ansible

About This Book

• Discover how Ansible works in detail
• Explore use cases for Ansible's advanced features including task delegation, fast failures, and serial task execution
• Extend Ansible with custom modules, plugins, and inventory sources

Who This Book Is For

This book is intended for Ansible developers and operators who have an understanding of the core elements and applications but are now looking to enhance their skills in applying automation using Ansible.

What You Will Learn

• Understand Ansible's code and logic flow
• Safeguard sensitive data within Ansible
• Access and manipulate complex variable data within Ansible playbooks
• Handle task results to manipulate change and failure definitions
• Organize Ansible content into a simple structure
• Craft a multi-tier rollout playbook utilizing load balancers and manipulating your monitoring system
• Utilize advanced Ansible features to orchestrate rolling updates with almost no service disruptions
• Troubleshoot Ansible failures to understand and resolve issues
• Extend Ansible with custom modules, plugins, or inventory sources

In Detail

Automation is critical to success in the world of DevOps. How quickly and efficiently an application deployment can be automated, or a new infrastructure can be built up, can be the difference between a successful product or a failure. Ansible provides a simple yet powerful automation engine. Beyond the basics of Ansible lie a host of advanced features which are available to help you increase efficiency and accomplish complex orchestrations with ease.

This book provides you with the knowledge you need to understand how Ansible works at a fundamental level and leverage its advanced capabilities. You'll learn how to encrypt Ansible content at rest and decrypt data at runtime. You will master the advanced features and capabilities required to tackle the complex automation challenges of today and beyond. You will gain detailed knowledge of Ansible workflows, explore use cases for advanced features, craft well thought out orchestrations, troubleshoot unexpected behaviour, and extend Ansible through customizations. Finally, you will discover the methods used to examine and debug Ansible operations, helping you to understand and resolve issues.

Style and approach

A clear, practical guide that covers best practise, system architecture and design aspects that will help you master Ansible with ease.

Mastering Ansible

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Table of Contents

Mastering Ansible

Credits

About the Author

Acknowledgment

About the Reviewers

www.PacktPub.com

Support files, eBooks, discount offers, and more

Why subscribe?

Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. System Architecture and Design of Ansible

Ansible version and configuration

Inventory parsing and data sources

The static inventory

Inventory variable data

Dynamic inventories

Run-time inventory additions

Inventory limiting

Playbook parsing

Order of operations

Relative path assumptions

Play behavior keys

Host selection for plays and tasks

Play and task names

Module transport and execution

Module reference

Module arguments

Module transport and execution

Task performance

Variable types and location

Variable types

Accessing external data

Variable precedence

Precedence order

Extra-vars

Connection variables

Most everything else

The rest of the inventory variables

Facts discovered about a system

Role defaults

Merging hashes

Summary

2. Protecting Your Secrets with Ansible

Encrypting data at rest

Things Vault can encrypt

Creating new encrypted files

The password prompt

The password file

The password script

Encrypting existing files

Editing encrypted files

Password rotation for encrypted files

Decrypting encrypted files

Executing ansible-playbook with Vault-encrypted files

Protecting secrets while operating

Secrets transmitted to remote hosts

Secrets logged to remote or local files

Summary

3. Unlocking the Power of Jinja2 Templates

Control structures

Conditionals

Inline conditionals

Loops

Filtering loop items

Loop indexing

Macros

Macro variables

name

arguments

defaults

catch_kwargs

catch_varargs

caller

Data manipulation

Syntax

Useful built-in filters

default

count

random

round

Useful Ansible provided custom filters

Filters related to task status

shuffle

Filters dealing with path names

basename

dirname

expanduser

Base64 encoding

Searching for content

Omitting undefined arguments

Python object methods

String methods

List methods

int and float methods

Comparing values

Comparisons

Logic

Tests

Summary

4. Controlling Task Conditions

Defining a failure

Ignoring errors

Defining an error condition

Defining a change

Special handling of the command family

Suppressing a change

Summary

5. Composing Reusable Ansible Content with Roles

Task, handler, variable, and playbook include concepts

Including tasks

Passing variable values to included tasks

Passing complex data to included tasks

Conditional task includes

Tagging included tasks

Including handlers

Including variables

vars_files

Dynamic vars_files inclusion

include_vars

extra-vars

Including playbooks

Roles

Role structure

Tasks

Handlers

Variables

Modules

Dependencies

Files and templates

Putting it all together

Role dependencies

Role dependency variables

Tags

Role dependency conditionals

Role application

Mixing roles and tasks

Role sharing

Ansible Galaxy

Summary

6. Minimizing Downtime with Rolling Deployments

In-place upgrades

Expanding and contracting

Failing fast

The any_errors_fatal option

The max_fail_percentage option

Forcing handlers

Minimizing disruptions

Delaying a disruption

Running destructive tasks only once

Summary

7. Troubleshooting Ansible

Playbook logging and verbosity

Verbosity

Logging

Variable introspection

Variable sub elements

Subelement versus Python object method

Debugging code execution

Debugging local code

Debugging inventory code

Debugging Playbook code

Debugging runner code

Debugging remote code

Debugging the action plugins

Summary

8. Extending Ansible

Developing modules

The basic module construct

Custom modules

Simple module

Module documentation

Providing fact data

Check mode

Supporting check mode

Handling check mode

Developing plugins

Connection type plugins

Shell plugins

Lookup plugins

Vars plugins

Fact caching plugins

Filter plugins

Callback plugins

Action plugins

Distributing plugins

Developing dynamic inventory plugins

Listing hosts

Listing host variables

Simple inventory plugin

Optimizing script performance

Summary

Index

Mastering Ansible

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the authornor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: November 2015

Production reference:1191115

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B32PB, UK.

ISBN 978-1-78439-548-3

www.packtpub.com

Credits

Author

Jesse Keating

Reviewers

Ryan Eschinger

Sreenivas Makam

Tim Rupp

Sawant Shah

Patrik Uytterhoeven

Acquisition Editor

Meeta Rajani

Content Development Editor

Zeeyan Pinheiro

Technical Editor

Rohan Uttam Gosavi

Copy Editor

Pranjali Chury

Project Coordinator

Nidhi Joshi

Proofreader

Safis Editing

Indexer

Monica Ajmera Mehta

Graphics

Disha Haria

Production Coordinator

Arvindkumar Gupta

Cover Work

Arvindkumar Gupta

About the Author

Jesse Keating is an accompl...

Table of contents

• Mastering Ansible