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.
Note
If you're interested more in the idea of the CD process, have a look at an excellent book by Jez Humble and David Farley, Continuous Delivery: Reliable Software Releases through Build, Test, and Deployment Automation.
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 used instead of Ansible. This is why each chapter begins with the general description of why such a tool is necessary and its role in the whole process. Then, the exact tool is described in comparison to its substitutes. That form gives you the flexibility to choose the right one for your environment.
Another approach could be to describe the CD process on the level of ideas; however, I strongly believe that giving an exact example with the code extract, something that readers can run by themselves, results in a much better understanding of the concept.
Note
There are two ways to read this book. The first is to read and understand the concepts of the CD process. The second is to create your own environment and execute all scripts while reading to understand the details.
Let's have a quick look at the tools we will use throughout this book. This section, however, is only a brief introduction to each technology—much more detail will be presented as this book proceeds.
Docker, as the clear leader of the containerization movement, has dominated the software industry in recent years. It allows us to package an application in the environment-agnostic image and therefore treats servers as a farm of resources, rather than machines that must be configured for each application. Docker was a clear choice for this book because it perfectly fits the (micro) service world and the CD process.
Docker entails a number of additional technologies, which are as follows:
- Docker Hub: This is a registry for Docker images
- Kubernetes: This is a container orchestrator
Jenkins is by far the most popular automation server on the market. It helps to create CI and CD pipelines and, in general, any other automated sequence of scripts. Highly plugin-oriented, it has a great community that constantly extends it with new features. What's more, it allows us to write the pipeline as code and supports distributed build environments.
Ansible is an automation tool that helps with software provisioning, configuration management, and application deployment. It is trending faster than any other configuration management engine and will soon overtake its two main competitors: Chef and Puppet. It uses agentless architecture and integrates smoothly with Docker.
GitHub is definitely the best of all hosted version control systems. It provides a very stable system, a great web-based UI, and a free service for public repositories. Having said that, any source control management service or tool will work with CD, irrespective of whether it's in the cloud or self-hosted, and whether it's based on Git, SVN, Mercurial, or any other tool.
Java has been the most popular programming language for years. That is why it is being used for most code examples in this book. Together with Java, most companies develop with the Spring framework, so we used it to create a simple web service needed to explain some concepts. Gradle is used as a build tool. It's still less popular than Maven, but is, trending much faster. As always, any programming language, framework, or build tool can be exchanged and the CD process would stay the same, so don't worry if your technology stack is different.