There are two major software development evolutions that enabled the popularity of Docker and Kubernetes. One is the adoption of a microservices architectural style. Microservices allow an application to be built from a collection of small services that each serve a specific function. The other evolution that enabled Docker and Kubernetes is DevOps. DevOps is a set of cultural practices that allows people, processes, and tools to build and release software faster, more frequently, and more reliably.

Although you can use both Docker and Kubernetes without using either microservices or DevOps, the technologies are most widely adopted for deploying microservices using DevOps methodologies.

In this section, we'll discuss both evolutions, starting with microservices.

Microservices

Software development has drastically evolved over time. Initially, software was developed and run on a single system, typically a mainframe. A client...

A form of container technology has existed in the Linux kernel since the 1970s. The technology powering today's containers, called cgroups, was introduced into the Linux kernel in 2006 by Google. The Docker company popularized the technology in 2013 by introducing an easy developer workflow. The company gave its name to the technology, so the name Docker can refer to both the company as well as the technology. Most commonly though, we use Docker to refer to the technology.

Docker as a technology is both a packaging format and a container runtime. We refer to packaging as an architecture that allows an application to be packaged together with its dependencies, such as binaries and runtime. The runtime points at the actual process of running the container images.

You can experiment with Docker by creating a free Docker account at Docker Hub (https://hub.docker.com/) and using that login to open Docker Labs (https://labs.play-with-docker.com...

Building and running a single container seems easy enough. However, things can get complicated when you need to run multiple containers across multiple servers. This is where a container orchestrator can help. A container orchestrator takes care of scheduling containers to be run on servers, restarting containers when they fail, moving containers to a new host when that host becomes unhealthy, and much more.

The current leading orchestration platform is Kubernetes (https://kubernetes.io/). Kubernetes was inspired by the Borg project in Google, which, by itself, was running millions of containers in production.

Kubernetes takes a declarative approach to orchestration; that is, you specify what you need and Kubernetes takes care of deploying the workload you specified. You don't need to start these containers manually yourself anymore, as Kubernetes will launch the Docker containers you specified.

Note

Although Kubernetes...

Azure Kubernetes Service (AKS) makes creating and managing Kubernetes clusters easier.

A typical Kubernetes cluster consists of a number of master nodes and a number of worker nodes. A node within Kubernetes is equivalent to a virtual machine (VM). The master nodes contain the Kubernetes API and a database that contains the cluster state. The worker nodes are the VMs that run your actual workload.

AKS makes it a lot easier to create a cluster. When you create an AKS cluster, AKS sets up the Kubernetes master for you, free of charge. AKS will then create VMs in your subscription, and turn those VMs into worker nodes of your Kubernetes cluster in your network. You only pay for those VMs; you don't pay for the master.

Within AKS, Kubernetes Services are integrated with Azure Load Balancer and Kubernetes Ingresses are integrated with the application gateway. Azure Load Balancer is a layer-4 network load balancer Service; the application gateway is...

In this chapter, we introduced the concepts of Docker and Kubernetes. We ran a number of containers, starting with an existing image and then using an image we built ourselves. After that demo, we explored three essential Kubernetes objects: the Pod, the Deployment, and the Service.

This provides the common context for the remaining chapters, where you will deploy Dockerized applications in Microsoft AKS. You will see how the AKS Platform as a Service (PaaS) offering from Microsoft streamlines Deployment by handling many of the management and operational tasks that you would have to do yourself if you managed and operated your own Kubernetes infrastructure.

In the next chapter, we will introduce the Azure portal and its components in the context of creating your first AKS cluster.