3.webapp-deployment.yaml

# Deployment to control creation of pods and update the containers
apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp
  namespace: demo
  labels:
    app: demo
    tier: frontend
spec:
  revisionHistoryLimit: 3 # Limit of history maintained by deployment, useful for rollback
  replicas: 3 # Minimum number of replicase gauranteed
  strategy: # Upgrade strategy 
    type: RollingUpdate # Can be either a "RollingUpdate" Or "Recreate"
    rollingUpdate: 
      maxUnavailable: 1 # Maximum number of old pods that are unavailable during upgrade, can be a percent too
      maxSurge : 1 # The maximum number of pods that can be scheduled above the desired number of pods
  # Below definition is simliar to a replicaset deployed in 2.webapp-replicaset.yaml
  selector:
    matchLabels:
      tier: frontend
  template:
    metadata:
      labels:
        tier: frontend
    spec:
      containers:
        - name: webapp
          image: pratapgowda/demo-webapp:1.0
          imagePullPolicy: IfNotPresent
          ports:
            - containerPort: 8080
          volumeMounts:
            - name: workdir
              mountPath: /usr/share/webapp/html
          resources:
            limits:
              cpu: "500m"
              memory: 1G
            requests:
              cpu: "25m"
              memory: 100Mi
          livenessProbe:
            httpGet:
              path: /health
              port: 8080
            initialDelaySeconds: 3
            periodSeconds: 3
          readinessProbe:
            httpGet:
              path: /health
              port: 8080
            initialDelaySeconds: 3
            periodSeconds: 3
        - name: sidecar
          image: busybox
          imagePullPolicy: IfNotPresent
          resources:
            limits:
              cpu: "500m"
              memory: 1G
            requests:
              cpu: "25m"
              memory: 100Mi
          command: 
            - sleep
            - "6000"
      # These containers are run during pod initialization
      initContainers:
        - name: initializer
          image: pratapgowda/demo-initializer
          imagePullPolicy: IfNotPresent
          env:
            - name: WAIT_IN_SECS
              value: "1"
          volumeMounts:
            - name: workdir
              mountPath: "/work-dir"
      dnsPolicy: Default
      volumes:
        - name: workdir
          emptyDir: {}