Preface

13

Structure

15

What You Should Already Know Now

16

What You Will Learn

17

Important to Know

17

Book Resources

19

1 Introduction to Kubernetes

21

1.1 Basic Principles and Concepts: Why Use Container Clusters at All?

21

1.1.1 Why Use Containers at All?

23

1.1.2 Why You Need a Container Management Tool

27

1.1.3 Of Pets and Cattle

28

1.1.4 Stateless and Stateful Applications

29

1.1.5 Separation of Concerns

31

1.2 Kubernetes, the Tool of Choice

34

1.2.1 Why Do Companies Want to Use Kubernetes?

34

1.2.2 The Promise of Kubernetes

37

1.2.3 Major Features

41

1.2.4 For Which Companies Is Kubernetes Useful?

42

1.2.5 Which Companies Should Not Use Kubernetes?

44

1.3 Architecture and Components

45

1.3.1 Master Nodes

46

1.3.2 Worker Nodes

49

1.3.3 API Call Flow

51

1.4 A Kubernetes Cluster on Your Computer

53

1.4.1 Minikube on macOS

54

1.4.2 Minikube on Linux

55

1.4.3 Minikube on Windows

57

1.4.4 Launching Minikube

58

1.4.5 Controlling Minikube

58

1.4.6 Possible Errors when Starting Minikube

59

1.4.7 Container Registry of Minikube

59

1.5 Interaction with Kubernetes via the Command Line and Dashboard

61

1.5.1 Minikube Comes With kubectl

61

1.5.2 Installing kubectl

61

1.5.3 Accessing the Cluster Using Kubeconfig

65

1.5.4 Namespaces

67

1.5.5 kubectl Commands

68

1.5.6 Switching Clusters and Namespaces Easily

77

1.5.7 The Kubernetes Dashboard

78

1.6 Lens: The IDE for Kubernetes

81

1.6.1 Overview of Lens

82

1.6.2 Advantages over the Kubernetes Dashboard

83

1.6.3 The Lens Reference

86

1.7 The Kubernetes Cluster from Raspberry Pis

89

1.7.1 Choosing the Right Raspberry Pis

90

1.7.2 Installation of Kubernetes

92

1.7.3 Using the Kubeconfig File of the Pi Cluster

93

2 Basic Objects and Concepts in Kubernetes

95

2.1 Pod and Container Management

98

2.1.1 Container Engines

101

2.1.2 Your First Own Pod

104

2.1.3 Multiple Containers within a Pod

106

2.1.4 Communication between Containers

109

2.1.5 Init Container

110

2.1.6 Pod Phases and Container Statuses

113

2.1.7 The Restart Policy of Pods

114

2.1.8 When the Pod Comes to an End

115

2.2 Annotations and Labels

118

2.2.1 Using Labels and Selectors

119

2.2.2 Field Selectors

121

2.2.3 NodeSelector

122

2.2.4 Node Affinity and Antiaffinity

124

2.2.5 Pod Affinity and Antiaffinity

128

2.2.6 Taints and Tolerations

133

2.2.7 Annotations

136

2.3 Deployments and ReplicaSets

138

2.3.1 The Role of ReplicaSets

139

2.3.2 Creating Deployments

142

2.3.3 Rolling Updates via the Deployment Object

144

2.3.4 Rollback via Deployment

150

2.4 ConfigMaps and Secrets

152

2.4.1 What Are ConfigMaps?

154

2.4.2 What Are Secrets?

162

2.5 Establishing a Communication with Services and an Ingress

171

2.5.1 Communication between Pods

173

2.5.2 Communication via a Service

174

2.5.3 Communication via Ingress

180

3 Everything as Code: Tools and Principles for Kubernetes Operations

187

3.1 Declarative Configurations

188

3.2 YAML: The Language for Kubernetes

192

3.2.1 Basics of YAML Syntax

192

3.2.2 Data Types in YAML

194

3.2.3 Anchors and Aliases

196

3.2.4 Single-Line YAML Notation in Documentation

197

3.2.5 Weaknesses of YAML

197

3.2.6 Tips for Practical Use

199

3.3 Version Management of Kubernetes Manifests

200

3.3.1 Using Git

201

3.3.2 Managing Numerous Kubernetes Manifests

203

3.3.3 Branching Strategies

207

3.3.4 Division of the Repositories

211

3.4 Continuous Integration and Continuous Delivery

213

3.4.1 Pipeline Steps for Kubernetes

213

3.4.2 Pipeline Architectures

218

3.4.3 GitOps

223

3.5 Templating Using Kustomize

225

3.5.1 Basic Principles of Kustomize

226

3.5.2 Resource Generator

231

3.5.3 More Kustomize Built-Ins

233

3.5.4 Conclusion on Kustomize

234

4 Advanced Objects and Concepts in Kubernetes

235

4.1 DaemonSets

236

4.2 Jobs in Kubernetes

239

4.2.1 Real-Life Kubernetes Jobs

240

4.2.2 Queue Worker with RabbitMQ

242

4.2.3 Kubernetes CronJobs

246

4.3 Custom Resources and Custom Resource Definitions

248

4.3.1 Example: A Monitoring CR

249

4.3.2 Validation in CRD

252

4.3.3 Operators

255

4.4 Downward API

258

4.5 Pod Priority and Preemption

261

4.6 Versioning Objects in Kubernetes

263

5 Stateful Applications and Storage

265

5.1 Stateful Applications in Kubernetes through StatefulSets

266

5.1.1 Pod Management Policy

269

5.1.2 Strategies for Updates

270

5.1.3 Retention Policy for Persistent Volume Claims

272

5.2 Persistent Volumes and Persistent Volume Claims

273

5.2.1 Storage Types for PVs

278

5.2.2 CSI Drivers for External Storage Media

281

5.2.3 Storage Classes and Dynamic PVs

283

5.2.4 PostgreSQL as StatefulSet with Persistent Volume

286

5.3 Ephemeral Volumes

289

5.4 Other Features of Volumes

291

5.4.1 Volume Snapshots

292

5.4.2 Projected Volumes

295

6 Kubernetes Governance and Security: Prepare for Production

299

6.1 Pod Security

301

6.2 Pod Security Admission

304

6.3 Admission Controller

306

6.4 Kubernetes Policies

308

6.5 Policy Objects

311

6.6 Role-Based Access Control in Kubernetes

313

6.6.1 Subjects: Users, Groups, and Service Accounts

315

6.6.2 Roles and Role Bindings

317

6.6.3 Conclusion

319

7 Developing Applications for Kubernetes: Ready for Production

321

7.1 Managing Pod Resources

322

7.2 Readiness, Liveness, and Startup Probes

325

7.2.1 How to Define Probes

328

7.2.2 Testing Probes Using an Example

330

7.3 Scaling and Load Balancing

335

7.3.1 Horizontal Pod Autoscaling

335

7.3.2 Vertical Pod Autoscaling

339

7.3.3 Cluster Autoscaler

341

7.4 Monitoring

342

7.4.1 Introduction: Prometheus, Grafana, and Alertmanager

343

7.4.2 Monitoring on the Pi Cluster

345

8 Orchestrating Kubernetes Using Helm

357

8.1 Helm: The Kubernetes Package Manager

358

8.1.1 Creating a First Helm Chart

361

8.1.2 Deploying a Helm Chart via the Command Line Interface

361

8.1.3 Setting Up and Managing a Helm Repository

363

8.1.4 Deploying a Helm Chart via Lens

365

8.1.5 Updating and Deleting Helm Releases

366

8.1.6 Downloading Helm Charts from a Repository

368

8.2 Reading and Developing Helm Charts

368

8.2.1 The Templating Engine and the Language of the Charts

369

8.2.2 Configuring Charts with Values

374

8.2.3 Conditions in Helm Templates

378

8.2.4 Other Operations and Control Structures

380

8.2.5 Helm Diff for Checking Changes

383

8.3 Developing Custom Charts

385

8.3.1 The Framework of Your Helm Chart

386

8.3.2 Packaging Charts and Storing Them in the Repository

387

8.3.3 Managing Dependencies in Helm Charts

390

8.4 Conclusion

394