Kubernetes Cookbook. Kirill Kazakov

and a single DNS name for a set of containers, and can load-balance the traffic between them, improving application accessibility and performance.

      – Health Monitoring and Self-healing

      Kubernetes regularly checks the health of nodes and containers and replaces containers that fail, kill those that don’t respond to user-defined health checks, and doesn’t advertise them to clients until they are ready to serve.

      – Automated Rollouts and Rollbacks

      Kubernetes enables you to describe the desired state for your deployed containers using deployments and automatically changes the actual state to the desired state at a controlled rate. This means you can easily and safely roll out new code and configuration changes. If something goes wrong, Kubernetes can rollback the change for you.

      – Secret and Configuration Management

      Kubernetes allows you to store and manage sensitive information such as passwords, OAuth tokens, and SSH keys using Kubernetes secrets. You can deploy and update secrets and application configuration without rebuilding your container images and without exposing secrets in your stack configuration.

      – Storage Orchestration

      Kubernetes allows you to automatically mount a storage system of your choice, whether from local storage, a public cloud provider, or a network storage system like NFS, iSCSI, etc.

      – Resource Management

      Kubernetes enables you to allocate specific amounts of CPU and memory (RAM) for each container. It can also limit the resource consumption for a namespace, thus ensuring that one part of your cluster doesn’t monopolize all available resources.

      The Role of Kubernetes

      In the modern cloud-native ecosystem, characterized by a multitude of services, technologies, and key components, Kubernetes stands out as a unified platform that orchestrates these diverse elements to ensure seamless operation. By abstracting the underlying infrastructure, Kubernetes enables developers to concentrate on building and deploying applications without needing to manage the specifics of the hosting environment. Effectively, Kubernetes operates equally well across cloud systems and on-premises infrastructure, providing versatility in deployment options.

      Kubernetes acts as a bridge between developers and infrastructure, offering a common framework and set of protocols. This functionality facilitates a more efficient and coherent interaction between those developing the applications and those managing the infrastructure. Through Kubernetes, the complexities of the infrastructure are masked, allowing developers to deploy applications that are scalable, resilient, and highly available, without needing deep knowledge of the underlying system details.

      Getting Started With Kubernetes

      This chapter covers

      – In-depth exploration of containerization with Docker, Podman, and Colima

      – Steps for effective application containerization

      – Introduction to Kubernetes and its role in orchestration

      – The deployment of applications through a first cluster was created with Minikube

      – Best practices and architectural considerations for migrating projects to Kubernetes

      – Core components of Kubernetes architecture

      – Fundamental concepts such as pods, nodes, and clusters

      – Overview of Kubernetes interfaces, including CNI, CSI, and CRI

      – Insights into command-line tools and plugins for efficient cluster management

      Key Learnings

      – Grasp the distinctions between Docker and Kubernetes containers.

      – Master effective project migration to Kubernetes.

      – Understand the fundamental architecture of Kubernetes.

      – Explore the Kubernetes ecosystem and interfaces.

      – Develop proficiency in managing Kubernetes using command-line tools.

      Recipes:

      – Wrap Your Application into a Container

      – Deploying Your First Application to Kubernetes

      – Use Podman for Kubernetes Migration

      – Lightweight Distributions: Setting Up k3s and microk8s

      – Enabling Calico CNI in Minikube and Exploring Its Features

      – Enhancing Your CLI Cluster Management with Krew: kubectx, kubens, kubetail, kubectl-tree, and kubecolor

      Introduction

      Welcome to Chapter 2, where we demystify Kubernetes, the cloud-native orchestration platform revolutionizing the deployment and management of containerized applications at scale. We will delve into containerization, starting with Docker and contrasting traditional packaging with containerization’s benefits in the software development lifecycle. Exploring tools like Podman and Colima, we analyze Docker alternatives and enhance container configurations. Moving to Kubernetes, we unveil its orchestration capabilities, introducing Pods, Nodes, Clusters, and Deployments. Practical examples guide you in setting up a Kubernetes Cluster with Minikube, touching on alternatives like K3s and Microk8s. The chapter concludes by highlighting Kubernetes’ extensible plugin ecosystem, empowering you with enhanced kubectl functionalities. By the end, you’ve navigated containerization, mastered Kubernetes essentials, and gained confidence in managing clusters.

      Docker and Kubernetes: Understanding Containerization

      Traditional Ways to Package Software

      Deploying software involves installing both the software itself and its dependencies on a server, coupled with the necessity of appropriate application configuration. This process demands considerable effort, time, and skills and is prone to errors.

      To streamline this cumbersome task, engineers have devised solutions such as Ansible, Puppet, or Chef, which automate the installation and configuration of software on servers. These tools adopt a declarative approach to system configuration and management, often emphasizing idempotency as a crucial feature. Another strategy to simplify installation in specific programming languages is to package the application into a single file. For instance, in the Java Runtime Environment (JRE), Java class files can be bundled using JAR files.

      Various methods can achieve a similar goal. Options like Omnibus or Homebrew packages offer diverse approaches to creating installers. Omnibus excels in crafting full-stack installers, while Homebrew packages leverage formulae written in Ruby. Alternatively, one can utilize virtual machine snapshots from VirtualBox or VMWare to encapsulate the entire state of the operating system alongside the installed application. Despite their continued use, these solutions exhibit notable limitations compared to Docker.

      Containerization

      As evidenced in the evolution of application packaging, containerization has emerged as a predominant format, encapsulating only essential libraries and dependencies for software delivery. It utilizes OS-level virtualization to run the code and create a single lightweight executable called a container that runs consistently on any infrastructure.

      This OS-level virtualization is a complex subject, and its intricacies are beyond the scope of this book. In essence, it is a technology in which the kernel permits the existence of multiple isolated user-space instances. Each instance is a virtual environment with CPU, memory, block I/O, network, and process space. This mechanism is made possible through various underlying technologies