kube-dns部署
kube-dns主要實現K8S集群內部服務發現以及集群內部通過服務名進行訪問。kubernetes集群中的服務都會有一個只用於內部訪問的ClusterIP,如下:
[root@master ~]# kubectl get svc NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.254.0.1 <none> 443/TCP 54d mysql NodePort 10.254.194.156 <none> 3306:8606/TCP 1d myweb NodePort 10.254.244.155 <none> 8080:8500/TCP 20h
kube-dns可以實現集群內部的服務名與ClusterIP的解析,實現服務之間通過服務名的訪問,方便部署管理
kubernetes提供的虛擬DNS服務1.6版本之後主要由kube-dns,dnsmasq,sidecar等3個容器組成。其中kube-dns監控kubernetes服務資源,並將記錄緩存至內存中;dnsmasq從kube-dns中獲取集群服務的DNS記錄並向集群提供DNS服務,sidecar負責另外兩個容器的健康監測。
二,安裝部署
安裝部署需要的yaml文件可以參考官網的github地址:https://github.com/kubernetes/kubernetes/tree/release-1.8/cluster/addons/dns;需要部署的文件為:kubedns-cm.yaml,kubedns-controller.yaml,kubedns-sa.yaml,kubedns-svc.yaml等
其中kubedns-cm.yaml,kubedns-sa.yaml兩個文件不需要更改,可以直接部署
文件內容如下:
[root@master dns]# cat kubedns-cm.yaml apiVersion: v1 kind: ConfigMap metadata: name: kube-dns namespace: kube-system labels: addonmanager.kubernetes.io/mode: EnsureExists [root@master dns]# cat kubedns-sa.yaml apiVersion: v1 kind: ServiceAccount metadata: name: kube-dns namespace: kube-system labels: kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: Reconcile
kubedns-controller.yaml文件修改後如下
# Copyright 2016 The Kubernetes Authors. # # # # Licensed under the Apache License, Version 2.0 (the "License"); # # you may not use this file except in compliance with the License. # # You may obtain a copy of the License at # # # # http://www.apache.org/licenses/LICENSE-2.0 # # # # Unless required by applicable law or agreed to in writing, software # # distributed under the License is distributed on an "AS IS" BASIS, # # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # # See the License for the specific language governing permissions and # # limitations under the License. # # # Should keep target in cluster/addons/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml # # in sync with this file. # # # __MACHINE_GENERATED_WARNING__ apiVersion: extensions/v1beta1 kind: Deployment metadata: name: kube-dns namespace: kube-system labels: k8s-app: kube-dns kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: Reconcile spec: # replicas: not specified here: # # 1. In order to make Addon Manager do not reconcile this replicas parameter. # # 2. Default is 1. # # 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on. strategy: rollingUpdate: maxSurge: 10% maxUnavailable: 0 selector: matchLabels: k8s-app: kube-dns template: metadata: labels: k8s-app: kube-dns annotations: scheduler.alpha.kubernetes.io/critical-pod: '' spec: tolerations: - key: "CriticalAddonsOnly" operator: "Exists" volumes: - name: kube-dns-config configMap: name: kube-dns optional: true containers: - name: kubedns image: gcr.io/google_containers/k8s-dns-kube-dns-amd64:1.14.4 resources: # TODO: Set memory limits when we've profiled the container for large # # clusters, then set request = limit to keep this container in # # guaranteed class. Currently, this container falls into the # # "burstable" category so the kubelet doesn't backoff from restarting it. 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 # we poll on pod startup for the Kubernetes master service and # # only setup the /readiness HTTP server once that's available. 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 - name: dnsmasq image: gcr.io/google_containers/k8s-dns-dnsmasq-nanny-amd64:1.14.4 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 - --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 # see: https://github.com/kubernetes/kubernetes/issues/29055 for details resources: requests: cpu: 150m memory: 20Mi volumeMounts: - name: kube-dns-config mountPath: /etc/k8s/dns/dnsmasq-nanny - name: sidecar image: gcr.io/google_containers/k8s-dns-sidecar-amd64:1.14.4 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,A - --probe=dnsmasq,127.0.0.1:53,kubernetes.default.svc.cluster.local,5,A ports: - containerPort: 10054 name: metrics protocol: TCP resources: requests: memory: 20Mi cpu: 10m dnsPolicy: Default # Don't use cluster DNS. serviceAccountName: kube-dns
需要修改的地方:
1)3個容器的鏡像根據自身條件定義
2)原文中變量 '_PILLAR__DNS__DOMAIN__'更改為自己設定的域名,通常為cluster.local
kubedns-svc.yaml文件內容如下:
[root@master dns]# cat kubedns-svc.yaml # Copyright 2016 The Kubernetes Authors. # # # # Licensed under the Apache License, Version 2.0 (the "License"); # # you may not use this file except in compliance with the License. # # You may obtain a copy of the License at # # # # http://www.apache.org/licenses/LICENSE-2.0 # # # # Unless required by applicable law or agreed to in writing, software # # distributed under the License is distributed on an "AS IS" BASIS, # # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # # See the License for the specific language governing permissions and # # limitations under the License. # # # __MACHINE_GENERATED_WARNING__ apiVersion: v1 kind: Service metadata: name: kube-dns namespace: kube-system labels: k8s-app: kube-dns kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: Reconcile kubernetes.io/name: "KubeDNS" spec: selector: k8s-app: kube-dns clusterIP: 10.254.0.2 ports: - name: dns port: 53 protocol: UDP - name: dns-tcp port: 53 protocol: TCP
此文件只需要修改其中clusterIP,將kube-dns服務的clusterIP固定,可自行定義為kube-apiserver配置中--service-cluster-ip-range定義的IP段內的任意IP
4個文件都生成之後則可以啟動了
kubectl create -f kubedns-cm.yaml -f kubedns-sa.yaml -f kubedns-controller.yaml -f kubedns-svc.yaml
啟動上述文件之後,還需要在kubelet配置中添加參數,指定DNS服務器:
... --cluster-dns=10.254.0.2 --cluster-domain=cluster.local ...
之後就可以在集群之間使用服務名互相訪問了
註意:
kube-dns按照上述文件進行配置只有1個副本,如果需要生成多個副本官網推薦以下兩種方案:
1)參考https://github.com/kubernetes/kubernetes/tree/release-1.8/cluster/addons/dns-horizontal-autoscaler
2)使用命令:kubectl --namespace=kube-system scale deployment kube-dns --replicas=<NUM_YOU_WANT>kube-dns部署