Feature/kubernetes Added example for kubernetes

cross_cutting/k8s/basic_example/README.adoc

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+== Run Example
+
+UPDATE
+
+In this example, a server (Original Server) inside the cluster connects to a database inside the cluster. To access data of the original server, another server(Access Server) inside the cluster is used. The aceess server can be accessed from outside the cluster. The access server  will communicate to the original server to retrieve data and sends it to the user.
+
+image::./docs/img/ClusterOverviewSimple.drawio.svg["ClusterOverviewSimple"]
+
+image::./docs/img/ClusterOverview.png["ClusterOverview"]
+
+=== Requirements
+
+- link:https://maven.apache.org/download.cgi[Maven] installed
+- link:https://taskfile.dev/installation/[Taskfile] installed
+- link:https://rancherdesktop.io/[Rancher Desktop] installed  with link:https://github.com/devonfw/ide[DevonIDE]
+- locale Kubernetes Cluster started
+- Behind VPN's activate wsl-vpnkit
+
+=== Installation
+[tabs]
+====
+Docker::
++
+--
+    - Run `task deployDocker`
+--
+Nerdctl::
++
+--
+    - Run `task deployNerd`
+--
+Docker behind VPN::
++
+--
+    - Run `task deployDockerVPN`
+--
+Nerdctl behind VPN::
++
+--
+    - Run `task deployNerdVPN`
+--
+====
+
+=== Uninstallation
+[tabs]
+====
+Docker::
++
+--
+    - Run `task removeDocker`
+--
+Nerdctl::
++
+--
+    - Run `task removeNerd`
+--
+Docker behind VPN::
++
+--
+    - Run `task removeDockerVPN`
+--
+Nerdctl behind VPN::
++
+--
+    - Run `task removeNerdVPN`
+--
+====
+
+=== Using VPN
+Using inside a VPN is currently only working with a work around:
+When running `kubectl` commands prepend `wsl`
+
+1. Start Rancher Desktop with vpn disabled
+2. Enable VPN
+3. Test connection with `wsl kubectl get all` 
+
+=== What happened
+
+1. For the original and access Server, a Dockerimage got created into a locale image repository
+2. The helm chart inside openapi_helm_chart got installed
+3. The Server and Database started and connected to each other
+4. When using a vpn the helm commands got routed through the wsl vpn kit
+
+=== Test
+At `http://localhost:5030/guest` there is a list of invited guests 
+
+If localhost is not working run 
+
+```
+kubectl get servie
+```
+
+Use the External Ip of the `openapi-server-access-service` instead of localhost

cross_cutting/k8s/basic_example/Taskfile.yml

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+version: '3'
+
+tasks:
+  deployNerd:
+    cmds:
+      - mvn -f ./server/access_server/pom.xml clean install
+      - mvn -f ./server/original_server/pom.xml clean install
+      - nerdctl build -t original-server-spring --namespace k8s.io ./server/original_server/
+      - nerdctl build -t access-server-spring --namespace k8s.io ./server/access_server/
+      - helm install openapi-example ./openapi_helm_chart/
+
+  removeNerd:
+    cmds:
+      - nerdctl image rm original-server-spring --namespace k8s.io -f
+      - nerdctl image rm access-server-spring --namespace k8s.io -f 
+      - helm uninstall openapi-example
+
+  deployDocker:
+    cmds:
+      - mvn -f ./server/access_server/pom.xml clean install
+      - mvn -f ./server/original_server/pom.xml clean install
+      - docker build -t original-server-spring ./server/original_server/
+      - docker build -t access-server-spring ./server/access_server/
+      - helm install openapi-example ./openapi_helm_chart/
+
+  removeDocker:
+    cmds:
+      - docker image rm original-server-spring -f
+      - docker image rm access-server-spring -f 
+      - helm uninstall openapi-example
+
+
+  deployNerdVPN:
+    cmds:
+      - mvn -f ./server/access_server/pom.xml clean install
+      - mvn -f ./server/original_server/pom.xml clean install
+      - nerdctl build -t original-server-spring --namespace k8s.io ./server/original_server/
+      - nerdctl build -t access-server-spring --namespace k8s.io ./server/access_server/
+      - wsl helm install openapi-example ./openapi_helm_chart/
+
+  removeNerdVPN:
+    cmds:
+      - nerdctl image rm original-server-spring --namespace k8s.io -f
+      - nerdctl image rm access-server-spring --namespace k8s.io -f 
+      - wsl helm uninstall openapi-example
+
+  deployDockerVPN:
+    cmds:
+      - mvn -f ./server/access_server/pom.xml clean install
+      - mvn -f ./server/original_server/pom.xml clean install
+      - docker build -t original-server-spring ./server/original_server/
+      - docker build -t access-server-spring ./server/access_server/
+      - wsl helm install openapi-example ./openapi_helm_chart/
+
+  removeDockerVPN:
+    cmds:
+      - docker image rm original-server-spring -f
+      - docker image rm access-server-spring -f 
+      - wsl helm uninstall openapi-example

cross_cutting/k8s/basic_example/openapi_helm_chart/.helmignore

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+# Patterns to ignore when building packages.
+# This supports shell glob matching, relative path matching, and
+# negation (prefixed with !). Only one pattern per line.
+.DS_Store
+# Common VCS dirs
+.git/
+.gitignore
+.bzr/
+.bzrignore
+.hg/
+.hgignore
+.svn/
+# Common backup files
+*.swp
+*.bak
+*.tmp
+*.orig
+*~
+# Various IDEs
+.project
+.idea/
+*.tmproj
+.vscode/

cross_cutting/k8s/basic_example/openapi_helm_chart/Chart.yaml

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+apiVersion: v2
+name: openapi-example
+description: A Helm chart for Kubernetes to depoy the open api server example
+
+# A chart can be either an 'application' or a 'library' chart.
+#
+# Application charts are a collection of templates that can be packaged into versioned archives
+# to be deployed.
+#
+# Library charts provide useful utilities or functions for the chart developer. They're included as
+# a dependency of application charts to inject those utilities and functions into the rendering
+# pipeline. Library charts do not define any templates and therefore cannot be deployed.
+type: application
+
+# This is the chart version. This version number should be incremented each time you make changes
+# to the chart and its templates, including the app version.
+# Versions are expected to follow Semantic Versioning (https://semver.org/)
+version: 0.1.0
+
+# This is the version number of the application being deployed. This version number should be
+# incremented each time you make changes to the application. Versions are not expected to
+# follow Semantic Versioning. They should reflect the version the application is using.
+# It is recommended to use it with quotes.
+appVersion: "1.16.0"

cross_cutting/k8s/basic_example/openapi_helm_chart/templates/config/accessServerConfig.yaml

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+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: openapi-server-access-config
+data:
+  mythaiapi_host_uri: "http://openapi-server-original-service.default.svc.cluster.local:5031/api/v1"

cross_cutting/k8s/basic_example/openapi_helm_chart/templates/config/databaseInitConfig.yaml

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+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: mysql-initdb-config
+data:
+  init.sql: |
+    CREATE DATABASE IF NOT EXISTS db_example;

cross_cutting/k8s/basic_example/openapi_helm_chart/templates/config/databaseSecret.yaml

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+apiVersion: v1
+kind: Secret
+metadata:
+    name: mysql-database-secret
+data:
+    mysql_root_username: cm9vdA==
+    mysql_root_password: cGFzc3dvcmQ=

cross_cutting/k8s/basic_example/openapi_helm_chart/templates/config/originalServerConfig.yaml

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+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: openapi-server-original-config
+data:
+  mysql_host: "mysql.default.svc.cluster.local"

cross_cutting/k8s/basic_example/openapi_helm_chart/templates/deployment/accessDeployment.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: openapi-server-access-deployment
+  labels:
+    app: openapi-server-access
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: openapi-server-access
+  template:
+    metadata:
+      labels:
+        app: openapi-server-access
+    spec:
+      containers:
+      - name: spring-access-server-spring
+        image: access-server-spring
+        imagePullPolicy: Never
+        ports:
+        - containerPort: 8080
+        env:
+        - name: MYTHAIAPI_HOST_URI
+          valueFrom:
+            configMapKeyRef:
+              name: openapi-server-access-config
+              key: mythaiapi_host_uri
+
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: openapi-server-access-service
+spec:
+  type: LoadBalancer
+  selector:
+    app: openapi-server-access
+  ports:
+    - protocol: TCP
+      port: 5030
+      targetPort: 8080
+
+

cross_cutting/k8s/basic_example/openapi_helm_chart/templates/deployment/originalDeployment.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: openapi-server-original-deployment
+  labels:
+    app: openapi-server-original
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: openapi-server-original
+  template:
+    metadata:
+      labels:
+        app: openapi-server-original
+    spec:
+      containers:
+      - name: spring-original-server-spring
+        image: original-server-spring
+        imagePullPolicy: Never
+        ports:
+        - containerPort: 8080
+        env:
+        - name: MYSQL_HOST
+          valueFrom:
+            configMapKeyRef:
+              name: openapi-server-original-config
+              key: mysql_host
+
+        - name: MYSQL_ROOT_PASSWORD
+          valueFrom:
+            secretKeyRef:
+              name: mysql-database-secret
+              key: mysql_root_password
+
+        - name: MYSQL_ROOT_USERNAME
+          valueFrom:
+            secretKeyRef:
+              name: mysql-database-secret
+              key: mysql_root_username
+
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: openapi-server-original-service
+spec:
+  selector:
+    app: openapi-server-original
+  ports:
+    - protocol: TCP
+      port: 5031
+      targetPort: 8080
+

cross_cutting/k8s/basic_example/openapi_helm_chart/templates/storage/createVolume.yaml

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+apiVersion: v1
+kind: PersistentVolume
+metadata:
+  name: mysql-pv-volume
+  labels:
+    type: local
+spec:
+  storageClassName: manual
+  capacity:
+    storage: 2Gi
+  accessModes:
+    - ReadWriteOnce
+  hostPath:
+    path: "/mnt/data"