The most accurate definition of the CD is stated by Jez Humble and reads as follows:

This definition covers the key points.

To understand it better, let's imagine a scenario. You are responsible for a product, let's say, the email client application. Users come to you with a new requirement: they want to sort emails by size. You decide that the development will take around one week. When can the user expect to use the feature? Usually, after the development is done, you hand over the completed feature first to the QA team and then to the operations team, which takes additional time, ranging from days to months...

We already know what the CD process is and why we use it. In this section, we describe how to implement it.

Let's start by emphasizing that each phase in the traditional delivery process is important. Otherwise, it would never have been created in the first place. No one wants to deliver software without testing it first! The role of the UAT phase is to detect bugs and to ensure that what developers created is what the customer wanted. The same applies to the operations team—the software must be configured, deployed to production, and monitored. That's out of the question. So, how do we automate the process so that we preserve all the phases? That is the role of the automated deployment pipeline, which consists of three stages, as presented in the following diagram:

The automated deployment pipeline is a sequence of scripts that...

The rest of this book is dedicated to technical details on how to implement a successful CD pipeline. The success of the process, however, depends not only on the tools we present throughout this book. In this section, we take a holistic look at the whole process and define the CD requirements in three areas:

• Your organization's structure and its impact on the development process
• Your products and their technical details
• Your development team and the practices you adopt

The way your organization works has a high impact on the success of introducing the CD process. It's a bit similar to introducing Scrum. Many organizations would like to use the Agile process, but...

We introduced the idea, benefits, and prerequisites with regard to the CD process. In this section, we will describe the tools that will be used throughout this book and their place in the system as a whole.

First of all, the specific tool is always less important than understanding its role in the process. In other words, any tool can be replaced with another one that plays the same role. For example, Jenkins can be replaced with Atlassian Bamboo, and Chef can be...

You can look at how this book is organized from two perspectives.

The first one is based on the steps of the automated deployment pipeline. Each chapter takes you closer to the complete CD process. If you look at the names of the chapters, some of them are even named like the pipeline phases:

• The CI pipeline
• Automated acceptance testing
• Configuration management with Ansible

The rest of the chapters give the introduction, summary, or additional information complementary to the process.

There is also a second perspective to the content of this book. Each chapter describes one piece of the environment, which, in turn, is well prepared for the CD process. In other words, the book presents, step by step, technology by technology, how to build a complete system. To help you get the feeling of what we plan to build throughout the book, let's now have...

In this chapter, we introduced the CD process starting from the idea, and discussed the prerequisites, to end up with tools that are used in the rest of this book. The key takeaway from this chapter is as follows: the delivery process currently used in most companies has significant shortcomings and can be improved using modern automation tools. The CD approach provides a number of benefits, of which the most significant ones are fast delivery, fast feedback cycle, and low-risk releases. The CD pipeline consists of three stages: CI, automated acceptance testing, and configuration management. Introducing CD usually requires a change in the organization's culture and structure. The most important tools in the context of CD are Docker, Jenkins, and Ansible.

In the next chapter, we'll introduce Docker and show you how to build a dockerized application.

To verify the knowledge acquired from this chapter, please answer the following questions:

1. What are the three phases of the traditional delivery process?
2. What are the three main stages of the CD pipeline?
3. Name at least three benefits of using CD.
4. What are the types of tests that should be automated as part of the CD pipeline?
5. Should we have more integration or unit tests? Explain why.
6. What does the term DevOps mean?
7. What are the software tools that will be used throughout this book? Name at least four.

To learn more about the concept of CD and its background, please refer to the following resources:

• Continuous Delivery by Jez Humble and David Farley: https://continuousdelivery.com/
• TestPyramid by Martin Fowler: https://martinfowler.com/bliki/TestPyramid.html
• Succeeding with Agile: Software Development Using Scrum by Mike Cohn