Revolutionizing Java: How Kubernetes 1.27 and Kyverno Supercharge Java App Startups

clusterRole.yaml

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: kyverno:update-pods
  labels:
    app.kubernetes.io/component: background-controller
    app.kubernetes.io/instance: kyverno
    app.kubernetes.io/part-of: kyverno
rules:
  - verbs:
      - patch
      - update
    apiGroups:
      - ''
    resources:
      - pods

cronJobSpec.yaml

# Example of specifying timeZone in CronJobSpec
apiVersion: batch/v1
kind: CronJob
metadata:
  name: timezone-specified-job
spec:
  schedule: "0 0 * * *"
  timeZone: "America/New_York"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: example-job
            image: job-image
          restartPolicy: OnFailure

cve.yaml

# Example of accessing the CVE feed
apiVersion: v1
kind: Pod
metadata:
  name: cve-feed-check
spec:
  containers:
    - name: cve-feed
      image: cve-feed-image
      command: ["sh", "-c", "curl https://kubernetes.io/cve-feed"]

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: sample-java
  namespace: demo
  labels:
    app: sample-java
spec:
  replicas: 1
  selector:
    matchLabels:
      app: sample-java
  template:
    metadata:
      labels:
        app: sample-java
    spec:
      containers:
      - name: sample-java
        image: kotlin-spring
        ports:
        - containerPort: 8080
        resources:
          limits:
            cpu: 4
            memory: "2Gi"
          requests:
            cpu: 0.1
            memory: "512Mi"
        resizePolicy: 
        - resourceName: "cpu"
          restartPolicy: "NotRequired"
        readinessProbe: 
          httpGet:
            path: /actuator/health/readiness
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 15
          periodSeconds: 5
          successThreshold: 1
          failureThreshold: 3

gRPC.yaml

# Example of using gRPC in readiness probes
apiVersion: v1
kind: Pod
metadata:
  name: grpc-readiness-example
spec:
  containers:
    - name: grpc-container
      image: grpc-image
      readinessProbe:
        grpc:
          port: 9090
          service: my-service
        initialDelaySeconds: 5
        periodSeconds: 10

kube.sh

# Example command to fetch logs from a node
kubectl get --raw "/api/v1/nodes/node-1.example/proxy/logs/?query=kubelet"

policy.yaml

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: resize-pod-policy
spec:
  mutateExistingOnPolicyUpdate: false
  rules:
    - name: resize-pod-policy
      match:
        any:
          - resources:
              kinds:
                - Pod/status
                - Pod
      preconditions: 
        all:
          - key: "{{request.object.status.containerStatuses[0].ready}}"
            operator: Equals
            value: true
      mutate:
        targets:
          - apiVersion: v1
            kind: Pod
            name: "{{request.object.metadata.name}}"
        patchStrategicMerge:
          spec:
            containers:
              - (name): sample-java
                resources:
                  limits:
                    cpu: 0.5 

terminationGracePeriodSeconds.yaml

# Example of setting terminationGracePeriodSeconds in a probe
apiVersion: v1
kind: Pod
metadata:
  name: graceful-shutdown-example
spec:
  containers:
    - name: example-container
      image: example-image
      livenessProbe:
        httpGet:
          path: /health
          port: liveness
        failureThreshold: 1
        periodSeconds: 60
        terminationGracePeriodSeconds: 60