Deploying a Tomcat Application on Kubernetes with Deployment and Service YAML

Pods and controllers in Kubernetes are linked via label selectors; controllers manage Pods for operations such as scaling and rolling updates.

A Deployment manages stateless applications, handling Pods and ReplicaSets, providing declarative updates, scaling, and rollback capabilities.

The following example creates a Deployment for a Tomcat container with three replicas and a corresponding Service of type NodePort to expose port 80.

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  labels:
    app: tomcat
  name: tomcat
spec:
  replicas: 3
  selector:
    matchLabels:
      app: tomcat
  template:
    metadata:
      labels:
        app: tomcat
    spec:
      imagePullSecrets:
      - name: registry-pull-secret
      containers:
      - image: tomcat
        imagePullPolicy: Always
        name: tomcat
        ports:
        - containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: tomcat-service
  labels:
    app: tomcat
spec:
  type: NodePort
  ports:
  - port: 80
    targetPort: 8080
  selector:
    app: tomcat

Apply the configuration with kubectl apply -f tomcat-deployment.yaml to create the Deployment and Service in the cluster.