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Kubernetes — Mission

Why I’m learning this

Section titled “Why I’m learning this”

I can build an image and run it; the WSL containers course ends there. Then someone says “deploy it on the cluster”, and I copy a YAML file from another service, change the name, and hope. When a pod restarts in a loop, or a Service answers nothing, I try things until it works, without knowing which one did.

I want to know what Kubernetes does with what I declare: which component acts on it, in what order, and what each status and event means. So that I can write manifests on purpose, deploy without interrupting the service, and find what is wrong from the cluster’s own answers.

Who this course is for

Section titled “Who this course is for”

You are a C# or Java developer, and you have built and run a container image. You don’t need to know Kubernetes or Linux networking. The images come from lesson 4 of WSL containers; the CI lessons send you to GitHub Actions, and lesson 13 to RabbitMQ for its Kubernetes operator.

The running example

Section titled “The running example”

The two small web APIs of the WSL containers course, an ASP.NET Core minimal API and a Spring Boot WebFlux API, run on a one-node kind cluster. Each lesson adds what a real deployment needs: probes and resources, rolling updates, a stable address, configuration, storage, security, packaging.

flowchart LR
    client["client<br/>curl, browser"] --> gw{{"Gateway<br/>csharp.example.test<br/>java.example.test"}}
    gw --> svc1["Service csharp-api"]
    gw --> svc2["Service java-reactor-api"]
    svc1 --> d1["Deployment csharp-api<br/>3 pods, ASP.NET Core"]
    svc2 --> d2["Deployment java-reactor-api<br/>2 pods, Spring Boot"]

Guitar Alchemist runs on Docker Compose and .NET Aspire, with a Kubernetes track planned; lesson 2 compares the probes of its deployment guide with its images.

By the end of this course, I will be able to

Section titled “By the end of this course, I will be able to”
  • explain what the API server, etcd, the scheduler, the controllers and the kubelet each do with a manifest;
  • run a local cluster with kind, and use kubectl against it without touching my other clusters;
  • write pods with the right probes, requests and limits, and read their conditions and events;
  • deploy the C# and Spring APIs with rolling updates, and roll back a failed release;
  • give them a stable address inside and outside the cluster, with Services, DNS, the Gateway API and Ingress;
  • configure them, give them storage, and run jobs and per-node agents;
  • control where pods run, how many run, and what they are allowed to do;
  • package a deployment with Helm and Kustomize, and deliver it with GitOps;
  • troubleshoot CrashLoopBackOff, ImagePullBackOff, Pending and OOMKilled from the cluster’s own information;
  • know what changes on AKS, EKS and GKE.

Outline

Section titled “Outline”
# Lesson You may already know
1 Architecture and a local cluster docker run, Docker Compose, a restart policy
2 Pods ASP.NET Core health checks, Spring Boot Actuator, docker logs
3 Deployments blue/green deployments, deployment slots in Azure App Service
4 Services and DNS a reverse proxy, YARP, Spring Cloud Gateway, /etc/hosts
5 Configuration: ConfigMaps and Secrets (coming next) appsettings.json, application.yml, environment variables
6 Storage: volumes, PersistentVolumes, StatefulSets Docker volumes, a database in a container
7 Jobs, CronJobs and DaemonSets BackgroundService, @Scheduled, a Windows service
8 Scheduling: affinity, taints, topology spread, priorities, disruption budgets
9 Scaling: HPA, metrics-server, VPA, cluster autoscaler App Service scale-out rules
10 Security: RBAC, ServiceAccounts, Pod Security Standards, NetworkPolicies ASP.NET Core authorization policies, Spring Security
11 Packaging: Helm and Kustomize NuGet and Maven, appsettings.Production.json
12 Observability and troubleshooting OpenTelemetry, dotnet-counters, Micrometer
13 Extending Kubernetes: CRDs and operators
14 Continuous delivery: GitOps with Argo CD or Flux, CI with GitHub Actions GitHub Actions
15 In production: AKS, EKS, GKE, costs, upgrades Azure, AWS or Google Cloud

Journal: what I tried, what surprised me, what I still need to verify.

Resources

Section titled “Resources”