apiVersion: apps/v1
kind: Deployment
metadata:
  name: coredns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/name: "CoreDNS"
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: EnsureExists
spec:
  # replicas: not specified here:
  # 1. Default is 1.
  # 2. Will be tuned in real time if DNS horizontal auto-scaling is turned on.
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
  selector:
    matchLabels:
      k8s-app: kube-dns
  template:
    metadata:
      labels:
        k8s-app: kube-dns
    spec:
      priorityClassName: system-cluster-critical
      serviceAccountName: coredns
      tolerations:
        - key: "CriticalAddonsOnly"
          operator: "Exists"
      nodeSelector:
        kubernetes.io/os: linux
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            - labelSelector:
                matchExpressions:
                  - key: k8s-app
                    operator: In
                    values: ["kube-dns"]
              topologyKey: kubernetes.io/hostname
      containers:
        - name: coredns
          image: k8s.gcr.io/coredns:1.3.1
          imagePullPolicy: IfNotPresent
          resources:
            limits:
              memory: 170Mi
            requests:
              cpu: 100m
              memory: 70Mi
          args: [ "-conf", "/etc/coredns/Corefile" ]
          volumeMounts:
            - name: config-volume
              mountPath: /etc/coredns
              readOnly: true
          ports:
            - containerPort: 53
              name: dns
              protocol: UDP
            - containerPort: 53
              name: dns-tcp
              protocol: TCP
            - containerPort: 9153
              name: metrics
              protocol: TCP
          securityContext:
            allowPrivilegeEscalation: false
            capabilities:
              add:
                - NET_BIND_SERVICE
              drop:
                - all
            readOnlyRootFilesystem: true
          livenessProbe:
            httpGet:
              path: /health
              port: 8080
              scheme: HTTP
            initialDelaySeconds: 60
            timeoutSeconds: 5
            successThreshold: 1
            failureThreshold: 5
          readinessProbe:
            httpGet:
              path: /health
              port: 8080
              scheme: HTTP
      dnsPolicy: Default
      volumes:
        - name: config-volume
          configMap:
            name: coredns
            items:
              - key: Corefile
                path: Corefile
