设置自定义 kube-dns Deployment

Standard

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本页面介绍如何为 Google Kubernetes Engine (GKE) Standard 模式集群运行 kube-dns 的自定义 Deployment。本页面不适用于 GKE Autopilot（在其中，由 Google 管理 kube-dns）。

注意：如果您运行 kube-dns 的自定义 Deployment，则必须使用安全补丁和更新使 kube-dns 映像保持最新。您可以从 kube-system 命名空间中的 kube-dns Deployment 获取最新映像。

概览

如需配置 kube-dns CPU、内存和其他参数，您必须运行自定义 Deployment 并停用 GKE 提供的 Deployment。您还可以按照本页面中的说明运行 Core DNS 或任何其他符合 Kubernetes DNS 规范的 DNS 提供商的自定义 Deployment。

如需详细了解 GKE 如何实现服务发现，请参阅服务发现和 DNS。

创建自定义 Deployment

1. 创建 kube-dns、Core DNS 或其他 DNS 提供商的Deployment 清单。

   以下示例 kube-dns 清单包含 -q 标志，以记录查询结果。将清单保存为 custom-kube-dns.yaml。

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: DNS_DEPLOYMENT_NAME
     namespace: kube-system
     annotations:
       deployment.kubernetes.io/revision: "1"
       k8s-app: kube-dns
   spec:
     selector:
       matchLabels:
         k8s-app: kube-dns
     strategy:
       rollingUpdate:
         maxSurge: 10%
         maxUnavailable: 0
       type: RollingUpdate
     template:
       metadata:
         creationTimestamp: null
         labels:
           k8s-app: kube-dns
       spec:
         containers:
         - name: kubedns
           image: registry.k8s.io/dns/k8s-dns-kube-dns:1.17.3
           resources:
             limits:
               memory: '170Mi'
             requests:
               cpu: 100m
               memory: '70Mi'
           livenessProbe:
             httpGet:
               path: /healthcheck/kubedns
               port: 10054
               scheme: HTTP
             initialDelaySeconds: 60
             timeoutSeconds: 5
             successThreshold: 1
             failureThreshold: 5
           readinessProbe:
             httpGet:
               path: /readiness
               port: 8081
               scheme: HTTP
             initialDelaySeconds: 3
             timeoutSeconds: 5
           args:
           - --domain=cluster.local.
           - --dns-port=10053
           - --config-dir=/kube-dns-config
           - --v=2
           env:
           - name: PROMETHEUS_PORT
             value: "10055"
           ports:
           - containerPort: 10053
             name: dns-local
             protocol: UDP
           - containerPort: 10053
             name: dns-tcp-local
             protocol: TCP
           - containerPort: 10055
             name: metrics
             protocol: TCP
           volumeMounts:
           - name: kube-dns-config
             mountPath: /kube-dns-config
           securityContext:
             allowPrivilegeEscalation: false
             readOnlyRootFilesystem: true
             runAsUser: 1001
             runAsGroup: 1001
         - name: dnsmasq
           image: registry.k8s.io/dns/k8s-dns-dnsmasq-nanny:1.17.3
           livenessProbe:
             httpGet:
               path: /healthcheck/dnsmasq
               port: 10054
               scheme: HTTP
             initialDelaySeconds: 60
             timeoutSeconds: 5
             successThreshold: 1
             failureThreshold: 5
           args:
           - -v=2
           - -logtostderr
           - -configDir=/etc/k8s/dns/dnsmasq-nanny
           - -restartDnsmasq=true
           - --
           - -k
           - --cache-size=1000
           - --no-negcache
           - --dns-forward-max=1500
           - --log-facility=-
           - --server=/cluster.local/127.0.0.1#10053
           - --server=/in-addr.arpa/127.0.0.1#10053
           - --server=/ip6.arpa/127.0.0.1#10053
           ports:
           - containerPort: 53
             name: dns
             protocol: UDP
           - containerPort: 53
             name: dns-tcp
             protocol: TCP
           resources:
             requests:
               cpu: 150m
               memory: 20Mi
           volumeMounts:
           - name: kube-dns-config
             mountPath: /etc/k8s/dns/dnsmasq-nanny
           securityContext:
             capabilities:
               drop:
               - all
               add:
               - NET_BIND_SERVICE
               - SETGID
         - name: sidecar
           image: registry.k8s.io/dns/k8s-dns-sidecar:1.17.3
           livenessProbe:
             httpGet:
               path: /metrics
               port: 10054
               scheme: HTTP
             initialDelaySeconds: 60
             timeoutSeconds: 5
             successThreshold: 1
             failureThreshold: 5
           args:
           - --v=2
           - --logtostderr
           - --probe=kubedns,127.0.0.1:10053,kubernetes.default.svc.cluster.local,5,SRV
           - --probe=dnsmasq,127.0.0.1:53,kubernetes.default.svc.cluster.local,5,SRV
           ports:
           - containerPort: 10054
             name: metrics
             protocol: TCP
           resources:
             requests:
               memory: 20Mi
               cpu: 10m
           securityContext:
             allowPrivilegeEscalation: false
             readOnlyRootFilesystem: true
             runAsUser: 1001
             runAsGroup: 1001
         dnsPolicy: Default
         restartPolicy: Always
         schedulerName: default-scheduler
         securityContext: {}
         serviceAccount: kube-dns
         serviceAccountName: kube-dns
         terminationGracePeriodSeconds: 30
         tolerations:
         - key: CriticalAddonsOnly
           operator: Exists
         volumes:
         - configMap:
             defaultMode: 420
             name: kube-dns
             optional: true
           name: kube-dns-config
   

   将 DNS_DEPLOYMENT_NAME 替换为自定义 kube-dns Deployment 的名称。

2. 将清单应用于集群：

   kubectl create -f custom-kube-dns.yaml
   

3. 验证 pod 是否正在运行：

   kubectl get pods -n kube-system -l=k8s-app=kube-dns
   

   输出类似于以下内容，显示自定义 kube-dns pod：

   NAME                               READY   STATUS    RESTARTS   AGE
   custom-kube-dns-5685645b44-kzs8w   3/3     Running   0          22h
   

   新 Deployment 的选择器与 kube-dns 相同，这意味着 pod 使用相同的 kube-dns 服务 IP 地址与运行自定义 kube-dns Deployment 的 pod 进行通信。

   完成此步骤后，您必须按照下一部分中的步骤缩减 kube-dns。

缩减 kube-dns

使用以下命令停用 kube-dns 部署和自动扩缩器，以停用由 GKE 管理的 kube-dns：

kubectl scale deployment --replicas=0 kube-dns-autoscaler --namespace=kube-system
kubectl scale deployment --replicas=0 kube-dns --namespace=kube-system

创建自定义自动扩缩器

如果您的自定义 DNS 需要自动扩缩，则必须配置和部署单独的自动扩缩器。kube-dns-autoscaler 仅扩缩集群上的默认 kube-dns Deployment。您还需要为自动扩缩器配置自定义 ClusterRole，并添加权限以修改自定义 kube-dns 部署。

1. 为自动扩缩器创建 ClusterRole 和 Deployment 清单，并将清单保存为 custom-dns-autoscaler.yaml：

   apiVersion: rbac.authorization.k8s.io/v1
   kind: ClusterRoleBinding
   metadata:
     name: system:custom-dns-autoscaler
   roleRef:
     apiGroup: rbac.authorization.k8s.io
     kind: ClusterRole
     name: system:custom-dns-autoscaler
   subjects:
   - kind: ServiceAccount
     name: kube-dns-autoscaler
     namespace: kube-system
   ---
   apiVersion: rbac.authorization.k8s.io/v1
   kind: ClusterRole
   metadata:
     name: system:custom-dns-autoscaler
   rules:
   - apiGroups:
     - ""
     resources:
     - nodes
     verbs:
     - list
     - watch
   - apiGroups:
     - apps
     resourceNames:
     - DNS_DEPLOYMENT_NAME
     resources:
     - deployments/scale
     verbs:
     - get
     - update
   - apiGroups:
     - ""
     resources:
     - configmaps
     verbs:
     - get
     - create
   ---
   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: custom-dns-autoscaler
     namespace: kube-system
     labels:
       k8s-app: custom-dns-autoscaler
   spec:
     selector:
       matchLabels:
         k8s-app: custom-dns-autoscaler
     template:
       metadata:
         labels:
           k8s-app: custom-dns-autoscaler
         annotations:
           seccomp.security.alpha.kubernetes.io/pod: 'docker/default'
       spec:
         priorityClassName: system-cluster-critical
         securityContext:
           supplementalGroups: [ 65534 ]
           fsGroup: 65534
         nodeSelector:
           kubernetes.io/os: linux
         containers:
         - name: autoscaler
           image: registry.k8s.io/cluster-proportional-autoscaler-amd64:1.7.1
           resources:
               requests:
                   cpu: "20m"
                   memory: "10Mi"
           command:
             - /cluster-proportional-autoscaler
             - --namespace=kube-system
             - --configmap=custom-dns-autoscaler
             - --target=Deployment/DNS_DEPLOYMENT_NAME
             - --default-params={"linear":{"coresPerReplica":256,"nodesPerReplica":16,"preventSinglePointFailure":true}}
             - --logtostderr=true
             - --v=2
         tolerations:
         - key: "CriticalAddonsOnly"
           operator: "Exists"
         serviceAccountName: kube-dns-autoscaler
   

2. 将清单应用于集群：

   kubectl create -f custom-dns-autoscaler.yaml
   

后续步骤

• 简要了解 GKE 如何提供代管式 DNS。
• 阅读服务和 Pod 的 DNS，大致了解如何在 Kubernetes 集群中使用 DNS。