Add Kubernetes support

k8s/README.md

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+# JHipster generated kubernetes configuration
+
+## Preparation
+
+You will need to push your image to a registry. If you have not done so, use the following commands to tag and push the images:
+
+```
+$ docker image tag jhonline jhipster-c4/jhonline
+$ docker push jhipster-c4/jhonline
+```
+
+## Deployment
+
+You can deploy all your apps by running the below bash command:
+
+```
+./kubectl-apply.sh
+```
+
+## Exploring your services
+
+
+Use these commands to find your application's IP addresses:
+
+```
+$ kubectl get svc jhonline
+```
+
+## Scaling your deployments
+
+You can scale your apps using
+
+```
+$ kubectl scale deployment <app-name> --replicas <replica-count>
+```
+
+## zero-downtime deployments
+
+The default way to update a running app in kubernetes, is to deploy a new image tag to your docker registry and then deploy it using
+
+```
+$ kubectl set image deployment/<app-name>-app <app-name>=<new-image> 
+```
+
+Using livenessProbes and readinessProbe allows you to tell kubernetes about the state of your apps, in order to ensure availablity of your services. You will need minimum 2 replicas for every app deployment, you want to have zero-downtime deployed. This is because the rolling upgrade strategy first kills a running replica in order to place a new. Running only one replica, will cause a short downtime during upgrades.
+
+
+
+## Troubleshooting
+
+> my apps doesn't get pulled, because of 'imagePullBackof'
+
+check the registry your kubernetes cluster is accessing. If you are using a private registry, you should add it to your namespace by `kubectl create secret docker-registry` (check the [docs](https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/) for more info)
+
+> my apps get killed, before they can boot up
+
+This can occur, if your cluster has low resource (e.g. Minikube). Increase the `initialDelySeconds` value of livenessProbe of your deployments
+
+> my apps are starting very slow, despite I have a cluster with many resources
+
+The default setting are optimized for middle scale clusters. You are free to increase the JAVA_OPTS environment variable, and resource requests and limits to improve the performance. Be careful!
+
+
+> my SQL based microservice stuck during liquibase initialization when running multiple replicas
+
+Sometimes the database changelog lock gets corrupted. You will need to connect to the database using `kubectl exec -it` and remove all lines of liquibases `databasechangeloglock` table.

k8s/jhonline-deployment.yml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: jhonline
+  namespace: default
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: jhonline
+      version: "v1"
+  template:
+    metadata:
+      labels:
+        app: jhonline
+        version: "v1"
+    spec:
+      initContainers:
+        - name: init-ds
+          image: busybox
+          command:
+            - '/bin/sh'
+            - '-c'
+            - |
+                while true
+                do
+                  rt=$(nc -z -w 1 jhonline-mysql 3306)
+                  if [ $? -eq 0 ]; then
+                    echo "DB is UP"
+                    break
+                  fi
+                  echo "DB is not yet reachable;sleep for 10s before retry"
+                  sleep 10
+                done
+      containers:
+      - name: jhonline-app
+        image: jhipster/jhipster-online
+        env:
+        - name: SPRING_PROFILES_ACTIVE
+          value: prod
+        - name: JHIPSTER_SECURITY_AUTHENTICATION_JWT_BASE64_SECRET
+          valueFrom:
+            secretKeyRef:
+              name: jwt-secret
+              key: secret
+        - name: SPRING_DATASOURCE_URL
+          value: jdbc:mysql://jhonline-mysql.default.svc.cluster.local:3306/jhonline?useUnicode=true&characterEncoding=utf8&useSSL=false
+        - name: JAVA_OPTS
+          value: " -Xmx256m -Xms256m"
+        resources:
+          requests:
+            memory: "256Mi"
+            cpu: "500m"
+          limits:
+            memory: "512Mi"
+            cpu: "1"
+        ports:
+        - name: http
+          containerPort: 8080
+        readinessProbe:
+          httpGet:
+            path: /management/health
+            port: http
+          initialDelaySeconds: 20
+          periodSeconds: 15
+          failureThreshold: 6
+        livenessProbe:
+          httpGet:
+            path: /management/health
+            port: http
+          initialDelaySeconds: 120

k8s/jhonline-mysql.yml

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+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+  name: jhonline-mysql
+  namespace: default
+spec:
+  replicas: 1
+  template:
+    metadata:
+      labels:
+        app: jhonline-mysql
+    spec:
+      volumes:
+      - name: data
+        emptyDir: {}
+      containers:
+      - name: mysql
+        image: mysql:8.0.13
+        env:
+        - name: MYSQL_USER
+          value: root
+        - name: MYSQL_ALLOW_EMPTY_PASSWORD
+          value: 'yes'
+        - name: MYSQL_DATABASE
+          value: jhonline
+        args:
+        - --lower_case_table_names=1
+        - --skip-ssl
+        - --character_set_server=utf8mb4
+        - --explicit_defaults_for_timestamp
+        ports:
+        - containerPort: 3306
+        volumeMounts:
+        - name: data
+          mountPath: /var/lib/mysql/
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: jhonline-mysql
+  namespace: default
+spec:
+  selector:
+    app: jhonline-mysql
+  ports:
+  - port: 3306

k8s/jhonline-service.yml

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+apiVersion: v1
+kind: Service
+metadata:
+  name: jhonline
+  namespace: default
+  labels:
+    app: jhonline
+spec:
+  selector:
+    app: jhonline
+  type: LoadBalancer
+  ports:
+  - name: http
+    port: 8080

k8s/jwt-secret.yml

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+apiVersion: v1
+kind: Secret
+metadata:
+  name: jwt-secret
+  namespace: default
+type: Opaque
+data:
+  secret: eHh4eHh4eHh4eHh4eHh4eHh4eHh4eHh4eHh4eHh4eHh4eHh4eHh4eA==

kubectl-apply.sh

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+#!/bin/bash
+# Files are ordered in proper order with needed wait for the dependent custom resource definitions to get initialized.
+# Usage: bash kubectl-apply.sh
+
+kubectl apply -f k8s/