Mastering Ansible - Second Edition
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About this ebook
- Learn how to extend Ansible with custom modules, plugins, and inventory sources
- Utilize advanced Ansible features to orchestrate rolling updates with little to no service disruptions
- An up-to-date book that brings to light the newly added features in Ansible 2.x
This book is 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.
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Mastering Ansible - Second Edition - Keating Jesse
Table of Contents
Mastering Ansible - Second Edition
Credits
About the Author
About the Reviewer
www.PacktPub.com
Why subscribe?
Customer Feedback
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
Downloading the color images of this book
Errata
Piracy
Questions
1. System Architecture and Design of Ansible
Ansible version and configuration
Inventory parsing and data sources
Static inventory
Inventory variable data
Dynamic inventories
Runtime inventory additions
Inventory limiting
Playbook parsing
Order of operations
Relative path assumptions
Play behavior directives
Execution strategies
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
Merging hashes
Summary
2. Protecting Your Secrets with Ansible
Encrypting data at rest
Things Vault can encrypt
Creating new encrypted files
Password prompt
Password file
Password script
Encrypting existing files
Editing encrypted files
Password rotation on encrypted files
Decrypting encrypted files
Executing Ansible-playbook with 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
Error recovery
Rescue
Always
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
Task includes with loops
Including handlers
Including variables
vars_files
Dynamic vars_files inclusion
include_vars
extra-vars
Including playbooks
Roles
Role structure
Tasks
Handlers
Variables
Modules and plugins
Dependencies
Files and templates
Putting it all together
Role dependencies
Role dependency variables
Tags
Role dependency conditionals
Role application
Mixing roles and tasks
Role includes
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
Serializing single tasks
Summary
7. Troubleshooting Ansible
Playbook logging and verbosity
Verbosity
Logging
Variable introspection
Variable sub elements
Subelement versus Python object method
Debugging code execution
Playbook debugging
Debugging local code
Debugging inventory code
Debugging playbook code
Debugging executor 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
The check mode
Supporting the check mode
Handling check mode
Developing plugins
Connection type plugins
Shell plugins
Lookup plugins
Vars plugins
The 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
Contributing to the Ansible project
Contribution submissions
The ansible repository
Executing tests
Unit tests
Integration tests
Code style tests
Making a pull request
Summary
9. Infrastructure Provisioning
Managing cloud infrastructure
Creating servers
Booting virtual servers
Adding to runtime inventory
Using OpenStack inventory source
Interacting with Docker containers
Building images
Building containers without a Dockerfile
Docker inventory
Previewing of Ansible container
Init
Build
Run
Summary
Mastering Ansible - Second Edition
Mastering Ansible - Second Edition
Copyright © 2017 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 author, nor 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
Second edition: March 2017
Production reference: 1270317
Published by Packt Publishing Ltd.
Livery Place
35 Livery Street
Birmingham
B3 2PB, UK.
ISBN 978-1-78712-568-1
www.packtpub.com
Credits
About the Author
Jesse Keating is an accomplished Ansible user, contributor, and presenter. He has been an active member of the Linux and open source community for over fifteen years. He has first-hand experience with a variety of IT activities, software development, and large-scale system administration. He has presented at numerous conferences and meet-ups, and has written many articles on a variety of topics.
About the Reviewer
Sreenivas Makam is a senior engineering manager at Cisco Systems, Bangalore. He has a master's in electrical engineering and has around 18 years’ experience in the networking industry. He has worked in both startups and big, established companies. His interests include Containers, SDN, network automation, devops, and cloud technologies, and he likes to try out and follow open source projects in these areas. His blog can be found at https://sreeninet.wordpress.com/, he has presentations at http://www.slideshare.net/SreenivasMakam, and his hacky code is at https://github.com/smakam. Sreenivas is a Docker Captain, (https://www.docker.com/community/docker-captains) and his blog articles have been published in Docker weekly newsletters. He can be reached on Twitter at @srmakam.
He has written Mastering CoreOS, also reviewed Mastering Ansible, CoreOS Cookbook, all by Packt Publishing.
It was extra special that my second daughter, Masha, was born while reviewing this book. Thanks to my daughters, Sasha and Masha, for keeping me energetic.
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Preface
Welcome to Mastering Ansible, your guide to a variety of advanced features and functionalities provided by Ansible, the automation and orchestration tool. This book will provide readers with the knowledge and skills to truly understand how Ansible functions at a fundamental level. This will allow readers to master the advanced capabilities needed to tackle complex automation challenges of today and the future. Readers will gain knowledge of Ansible workflows, explore use cases for advanced features, troubleshoot unexpected behavior, and extend Ansible through customization.
What this book covers
Chapter 1, System Architecture and Design of Ansible, looks at the ins and outs of how Ansible goes about performing tasks on behalf of an engineer, how it is designed, and how to work with inventory and variables.
Chapter 2, Protecting Your Secrets with Ansible, explores the tools available to encrypt data at rest and prevent secrets from being revealed at runtime.
Chapter 3, Unlocking the Power of Jinja2 Templates, states the varied uses of the Jinja2 templating engine within Ansible and discusses ways to make the most out of its capabilities.
Chapter 4, Controlling Task Conditions, describes the changing of the default behavior of Ansible to customize task error and change conditions.
Chapter 5, Composing Reusable Ansible Content with Roles, covers the approach to move beyond executing loosely-organized tasks on hosts to encapsulating clean and reusable abstractions to apply a specific functionality of a target set of hosts.
Chapter 6, Minimizing Downtime with Rolling Deployments, explains the common deployment and upgrade strategies to showcase relevant Ansible features.
Chapter 7, Troubleshooting Ansible, takes you through the various methods that can be employed to examine, introspect, modify, and debug the operations of Ansible.
Chapter 8, Extending Ansible, discovers the various ways in which new capabilities can be added to Ansible via modules, plugins, and inventory sources.
Chapter 9, Infrastructure Provisioning, will be working with cloud infrastructure providers and container systems to create an infrastructure to manage.
What you need for this book
To follow the examples provided in this book, you will need access to a computer platform capable of running Ansible. Currently, Ansible can be run on any machine with Python 2.6 or 2.7 installed (Windows isn't supported for the control machine). This includes Red Hat, Debian, CentOS, OS X, any of the BSDs, and so on.
This book uses the Ansible 2.2.x.x series release.
Ansible installation instructions can be found at http://docs.ansible.com/ansible/intro_installation.html.
Some examples use Docker, version 1.12.6. Docker installation instructions can be found at: http://www.docker.com/community-edition.
Who this book is for
This book is 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.
Conventions
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: We'll make use of this in a failed_when statement.
A block of code is set as follows:
- name: query sessions
command: /sbin/iscsiadm –m session
register: sessions
failed_when: sessions.rc not in (0, 21)
Any command-line input or output is written as follows:
$ source ./hacking/env-setup
Note
Warnings or important notes appear in a box like this.
Tip
Tips and tricks appear like this.
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Downloading the color images of this book
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Questions
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Chapter 1. System Architecture and Design of Ansible
This chapter provides a detailed exploration of the architecture and design of how Ansible goes about performing tasks on your behalf. We will cover the basic concepts of inventory parsing and how the data is discovered, and then dive into playbook parsing. We will take a walk through module preparation, transportation, and execution. Lastly, we will detail variable types and find out where variables can be located, the scope they can be used in, and how precedence is determined when variables are defined in more than one location. All these things will be covered in order to lay the foundation for mastering Ansible!
In this chapter, we will cover the following topics:
Ansible version and configuration
Inventory parsing and data sources
Playbook parsing
Execution strategies
Module transport and execution
Variable types and locations
Variable precedence
Ansible version and configuration
It is assumed that you have Ansible installed on your system. There are many documents out there that cover installing Ansible in a way that is appropriate for the operating system and version that you might be using. This book will assume the use of the Ansible 2.2.x.x version. To discover the version in use on a system with Ansible already installed, make use of the version argument, that is, either ansible or ansible-playbook:
Note
Note that ansible is the executable for doing adhoc one-task executions and ansible-playbook is the executable that will process playbooks for orchestrating many tasks.
The configuration for