Prerequisites and Environment Setup

Begin by verifying network connectivity between your build environment and the target database. Install the required Java Development Kit (JDK) and Maven compiler toolchain using your system's package manager.

sudo yum install java-11-openjdk-devel maven -y

Application Configuration and Compilation

Update the application configurasion file to reflect the correct data base connection parameters and server settings. Compile the project into a deployable archive, explicitly skipping unit tests to optimize build time.

vim src/main/resources/application.yml

server:
  port: 8080
spring:
  datasource:
    url: jdbc:mysql://db-cluster.internal:3306/app_db?useSSL=false&allowPublicKeyRetrieval=true
    username: deploy_user
    password: SecureP@ssw0rd
    driver-class-name: com.mysql.cj.jdbc.Driver

mvn clean package -DskipTests

Container Image Construction and Registry Push

Define a lightweight Docker image based on a preconfigured Tomcat runtime. Copy the compiled WAR artifact into the webapps directory, build the image, and authenticate before pushing to your preferred container registry.

vim Dockerfile

FROM tomcat:9.0-jdk17-slim
LABEL maintainer="devops-team"
RUN rm -rf /usr/local/tomcat/webapps/*
COPY target/app-service-1.0.war /usr/local/tomcat/webapps/ROOT.war
EXPOSE 8080

docker build -t registry.example.com/platform/web-app:v2.1 .
docker login registry.example.com
docker push registry.example.com/platform/web-app:v2.1

Kubernetes Deployment Manifest Generation

Generate a baseline Deployment specification using a dry-run strategy. Modify the manifest to set the desired replica count, verify label selectors, and apply the configuration to the cluster.

kubectl create deployment web-platform \
  --image=registry.example.com/platform/web-app:v2.1 \
  --dry-run=client -o yaml > deployment.yaml

vim deployment.yaml
###########################
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-platform
  labels:
    app: web-platform
spec:
  replicas: 3
  selector:
    matchLabels:
      app: web-platform
  template:
    metadata:
      labels:
        app: web-platform
    spec:
      containers:
      - name: app-container
        image: registry.example.com/platform/web-app:v2.1
        ports:
        - containerPort: 8080
#############################

kubectl apply -f deployment.yaml
kubectl get pods -l app=web-platform

Service Exposure and Traffic Routing

Create a Service resource to route external traffic to the running pods. Utilize a NodePort type to map an ephemeral host port to the internal application port for external accessibility.

kubectl expose deployment/web-platform \
  --port=80 \
  --target-port=8080 \
  --type=NodePort \
  --dry-run=client -o yaml > service.yaml

vim service.yaml
#################################
apiVersion: v1
kind: Service
metadata:
  name: web-platform-svc
  labels:
    app: web-platform
spec:
  type: NodePort
  ports:
  - port: 80
    protocol: TCP
    targetPort: 8080
    nodePort: 32088
  selector:
    app: web-platform
####################################

kubectl apply -f service.yaml

Once applied, the application can be accessed externally via any worker node IP address combined with the mapped port (e.g., http://<node-ip>:32088).

Operational Management: Scaling and Rollbacks

Track deployment revisions to facilitate quick recovery in case of deployment failures. Adjust the replica count dynamically to handle varying load requirements.

kubectl rollout history deployment/web-platform
kubectl rollout undo deployment/web-platform

kubectl scale deployment/web-platform --replicas=5