Übung Minikube-Demo

Voraussetzungen

docker / docker desktop

maven

MacOS: brew install maven
Windows
Linux: maven is installed, but not maybe not the newest

Minikube

Minikube is also available in "docker desktop" and can be activated.
minikube can also installed independently of "docker desktop".
- Installationsanweisungen

kubectl

Used for the communication with Minikube (and later on with the cloud).
Install kubectl

It is highly recommended to install autocompletion für kubectl.

kubectl autocomplete for zsh

source <(kubectl completion zsh)  # set up autocomplete in zsh into the current shell
echo '[[ $commands[kubectl] ]] && source <(kubectl completion zsh)' >> ~/.zshrc # add autocomplete permanently to your zsh shell

kubectl Quick Reference (Cheat Sheet)

1. Start minikube

We do not need minikube at the moment, but we will start to make sure that it is working.

minikube start

result

😄  minikube v1.32.0 on Darwin 14.3.1 (arm64)
✨  Automatically selected the docker driver
📌  Using Docker Desktop driver with root privileges
👍  Starting control plane node minikube in cluster minikube
🚜  Pulling base image ...
💾  Downloading Kubernetes v1.28.3 preload ...
    > preloaded-images-k8s-v18-v1...:  341.16 MiB / 341.16 MiB  100.00% 1.81 Mi
    > gcr.io/k8s-minikube/kicbase...:  410.57 MiB / 410.58 MiB  100.00% 1.36 Mi
🔥  Creating docker container (CPUs=2, Memory=7793MB) ...
🐳  Preparing Kubernetes v1.28.3 on Docker 24.0.7 ...
    ▪ Generating certificates and keys ...
    ▪ Booting up control plane ...
    ▪ Configuring RBAC rules ...
🔗  Configuring bridge CNI (Container Networking Interface) ...
🔎  Verifying Kubernetes components...
    ▪ Using image gcr.io/k8s-minikube/storage-provisioner:v5
🌟  Enabled addons: storage-provisioner, default-storageclass
🏄  Done! kubectl is now configured to use "minikube" cluster and "default" namespace by default

Falls die Meldung erscheint, dass der Cluster veraltet ist, dann minikube stop und minikube delete. Beim anschließenden minikube start wird ein Cluster mit aktueller kubernetes-Software erstellt.
Check, in the "🌟 Enabled addons:"-section, that metrics-server and dashboard are installed.
- When missing:
  minikube addons enable metrics-server minikube addons enable dashboard

check the successfull installation with

minikube addons list |grep enabled

result

| dashboard                   | minikube | enabled ✅   | Kubernetes                     |
| default-storageclass        | minikube | enabled ✅   | Kubernetes                     |
| metrics-server              | minikube | enabled ✅   | Kubernetes                     |
| storage-provisioner         | minikube | enabled ✅   | minikube                       |

1.1. Minikube configuration

For accessing minikube and later on k8s, we need kubectl.

check the correct configuration

 kubectl config view

result

apiVersion: v1
clusters:
- cluster:
    certificate-authority: /Users/stuetz/.minikube/ca.crt
    extensions:
    - extension:
        last-update: Sun, 17 Mar 2024 12:10:05 CET
        provider: minikube.sigs.k8s.io
        version: v1.32.0
      name: cluster_info
    server: https://127.0.0.1:59820
  name: minikube
contexts:
- context:
    cluster: minikube
    extensions:
    - extension:
        last-update: Sun, 17 Mar 2024 12:10:05 CET
        provider: minikube.sigs.k8s.io
        version: v1.32.0
      name: context_info
    namespace: default
    user: minikube
  name: minikube
current-context: minikube
kind: Config
preferences: {}
users:
- name: minikube
  user:
    client-certificate: /Users/stuetz/.minikube/profiles/minikube/client.crt
    client-key: /Users/stuetz/.minikube/profiles/minikube/client.key

 kubectl config get-contexts

result

CURRENT   NAME       CLUSTER    AUTHINFO   NAMESPACE
*         minikube   minikube   minikube   default

2. Overview

First we create a simple REST-endpoint with quarkus.
We create an uber-jar.
We build a docker image with the jar-filee.
We push the docker image to an image registry (ghcr.io).
We deploy the docker image to minikube.

3. Create the quarkus Project

mvn io.quarkus.platform:quarkus-maven-plugin:3.8.2:create \
    -DprojectGroupId=at.htl.minikube \
    -DprojectArtifactId=minikube-demo \
    -Dextensions='resteasy-reactive, smallrye-health'

or start the script create-project.sh

result

[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< org.apache.maven:standalone-pom >-------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] --------------------------------[ pom ]---------------------------------
[INFO]
[INFO] --- quarkus:3.7.3:create (default-cli) @ standalone-pom ---
[INFO] Looking for the newly published extensions in registry.quarkus.io
[INFO] -----------
[INFO] selected extensions:
- io.quarkus:quarkus-smallrye-health
- io.quarkus:quarkus-resteasy-reactive

[INFO]
applying codestarts...
[INFO] 📚 java
🔨 maven
📦 quarkus
📝 config-properties
🔧 tooling-dockerfiles
🔧 tooling-maven-wrapper
🚀 resteasy-reactive-codestart
🚀 smallrye-health-codestart
[INFO]
-----------
[SUCCESS] ✅  quarkus project has been successfully generated in:
--> /Users/stuetz/work/_delete/minikube-demo
-----------
[INFO]
[INFO] ========================================================================================
[INFO] Your new application has been created in /Users/stuetz/work/_delete/minikube-demo
[INFO] Navigate into this directory and launch your application with mvn quarkus:dev
[INFO] Your application will be accessible on http://localhost:8080
[INFO] ========================================================================================
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  4.232 s
[INFO] Finished at: 2024-02-19T08:12:54+01:00
[INFO] ------------------------------------------------------------------------

or create a project on quarkus.io - START CODING.

On quarkus.io you can also create a github-repo automatically.

4. Run the quarkus Project

cd minikube-demo
./mvnw clean quarkus:dev

5. Request the REST-Endpoints

Create a REST-Client
- New folder in project-Root: http-requests
- create a new file in this folder: requests.http

you can also use cURL:

curl -i http://localhost:8080/hello (1)

1	-i shows the header of the response.

result

HTTP/1.1 200 OK
content-length: 28
Content-Type: text/plain;charset=UTF-8

Hello from RESTEasy Reactive%

6. Create a .jar File (uber-jar)

6.1. What is a uber-jar?

6.2. How to create an uber-jar?

Precondition - add this entry to the application.properties

quarkus.package.type=uber-jar

./mvnw clean package

check, if the runner-jar is created

7. Create docker Image

Therefore, we need a Dockerfile.
There are already Dockerfiles in src/main/docker - these are not needed and can be deleted
Create a new Dockerfile in src/main/docker

result

tree

...
├── src
│   ├── main
│   │   ├── docker
│   │   │   └── Dockerfile
...

Dockerfile

FROM eclipse-temurin:17-jre

RUN mkdir -p /opt/application
COPY *-runner.jar /opt/application/backend.jar
WORKDIR /opt/application
CMD [ "java", "-jar", "backend.jar" ]

The following steps should be automated, but for now we do it manually:

cp src/main/docker/Dockerfile target
docker build --tag ghcr.io/htl-leonding/backend:latest ./target

docker image ls

result

REPOSITORY                       TAG           IMAGE ID       CREATED         SIZE
...
gghcr.io/htl-leonding/backend    latest        ae27690f900d   53 seconds ago   263MB
...

8. Docker image push to Docker Registry

docker login ghcr.io

You need a personal token to authenticate (click for instructions)

github - profile picture - Settings - Developer Settings - Personal access tokens - Tokens (classic)

Troubleshooting:

When your gh-user-name contains uppercase letters, change the name to lowercase.
When it still, does not work, then delete ~/.docker/config.json and try it again.

Push Container to docker registry

docker push ghcr.io/htl-leonding/backend:latest

result

The push refers to repository [ghcr.io/htl-leonding/backend]
5f70bf18a086: Layer already exists
2359f2e5d796: Pushed
08b2bdc5762e: Layer already exists
6e0f58883206: Layer already exists
eed4bd617b87: Layer already exists
65bb8dcc703b: Layer already exists
63aa4237e067: Layer already exists
98d1994bf6c1: Layer already exists
latest: digest: sha256:50c58e0426ad4b4335c791d7f60efcad24cc9c5554d5e7f35f0438186af508ca size: 1992

Make package public (click for instructions)

9. Configure kubernetes Deployment

check, if you are still in project root, then:

mkdir k8s
touch k8s/appsrv.yaml

k8s/appsrv.yaml

# Quarkus Application Server
apiVersion: apps/v1
kind: Deployment
metadata:
  name: appsrv

spec:
  replicas: 1
  selector:
    matchLabels:
      app: appsrv
  template:
    metadata:
      labels:
        app: appsrv
    spec:
      containers:
        - name: appsrv
          image: ghcr.io/htl-leonding/backend:latest (1)
          # remove this when stable. Currently we do not take care of version numbers
          imagePullPolicy: Always
          ports:
            - containerPort: 8080
          startupProbe:
            httpGet:
              path: /q/health
              port: 8080
            timeoutSeconds: 5
            initialDelaySeconds: 15
          readinessProbe:
            tcpSocket:
              port: 8080
            initialDelaySeconds: 5
            periodSeconds: 10
          livenessProbe:
            httpGet:
              path: /q/health
              port: 8080
            timeoutSeconds: 5
            initialDelaySeconds: 60
            periodSeconds: 120
---
apiVersion: v1
kind: Service
metadata:
  name: appsrv

spec:
  ports:
    - port: 8080
      targetPort: 8080
      protocol: TCP
  selector:
    app: appsrv

1	Check, that your image name is correct

You could also generate this file with kubectl

create deployment in minikube-instance

kubectl create deployment appsrv --image=ghcr.io/htl-leonding/backend:latest --port=8080

result

deployment.apps/appsrv created

write to file

kubectl get deployments/appsrv -o yaml > appsrv.yaml

create service in minikube-instance

kubectl expose deployments/appsrv --port=8080

exposing the port 8080

kubectl expose deployments/appsrv-depl --port=8080

10. Deploy to minikube the first time

kubectl apply -f k8s/appsrv.yaml

result

deployment.apps/appsrv created
service/appsrv created

10.1. Check the Success

minikube dashboard

result

🤔  Verifying dashboard health ...
🚀  Launching proxy ...
🤔  Verifying proxy health ...
🎉  Opening http://127.0.0.1:53209/api/v1/namespaces/kubernetes-dashboard/services/http:kubernetes-dashboard:/proxy/ in your default browser...

The following site should be opened in your browser
- if not just use minikube --url and copy the given url into your browser

We notice there are problems

10.2. Fix problems

We have problems with the jdk-version, because …
- The pom uses jdk-21
- The Docker image uses jdk-17
We decide to use jdk-17 and fix the pom.xml.

11. Re-Deploy to minikube

build and push the image

./mvnw clean package
cp src/main/docker/Dockerfile target
docker build --tag ghcr.io/htl-leonding/backend:latest ./target
docker push ghcr.io/htl-leonding/backend:latest

Redeploy the app

kubectl rollout restart deployment appsrv

Now you see the new pod is already running and the old (broken) pod is still alive.

The broken pods are now history

12. Port Forward from minikube

Port forwarding

kubectl port-forward appsrv-xxxxxx-xxxxx 8080:8080

Use kubectl-autocomplete for the appsrv

result

❯ kubectl port-forward appsrv-7964857d64-2bhcp 8080:8080
Forwarding from 127.0.0.1:8080 -> 8080
Forwarding from [::1]:8080 -> 8080

13. Access the App

curl -i http://localhost:8080/hello

result

HTTP/1.1 200 OK
content-length: 28
Content-Type: text/plain;charset=UTF-8

Hello from RESTEasy Reactive%

14. Troubleshooting

open an ssh-shell in minikube

minikube ssh

 __   ___     _   ___      __     _      _
 \ \ / (_)___| | | __|_ _ / _|___| |__ _| |
  \ V /| / -_) | | _|| '_|  _/ _ \ / _` |_|
   \_/ |_\___|_| |___|_| |_| \___/_\__, (_)
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