1、介紹
之前介紹過DNS的搭建(基於Kubernetes叢集部署skyDNS服務),但那個版本的DNS是隨著Kubernetes1.2釋出出來的,有點原始。本文主要講解Kubernetes1.4版本中的DNS外掛的安裝。與1.2版本相比,1.4中的DNS增加了解析Pod(HostName)對應的域名的新功能,且在部署上也有了一些變化。1.2中,需要部署etcd(或使用master上的Etcd)、kube2sky、skydns三個元件;1.4中,DNS元件由kubedns(監控Kubernetes中service變化)、dnsmasq(DNS服務)和一個健康檢查容器——healthz組成。
在搭建PetSet(寵物應用)時,系統首先要為PetSet設定一個HeadLess service,即service的ClusterIP顯示的設定成none,而對每一個有特定名稱的Pet(Named Pod),可以通過其HostName進行定址訪問。這就用到了1.4中的新功能。以下給出具體的搭建過程。
2、修改配置
2.1修改各個node上的kubelet
修改以下紅色部分,完成後重啟kubelet服務。
[root@k8s-node-1 ~]# cat /etc/kubernetes/kubelet ### # kubernetes kubelet (minion) config # The address for the info server to serve on (set to 0.0.0.0 or "" for all interfaces) KUBELET_ADDRESS="--address=0.0.0.0" # The port for the info server to serve on # KUBELET_PORT="--port=10250" # You may leave this blank to use the actual hostname #KUBELET_HOSTNAME="--hostname-override=127.0.0.1" KUBELET_HOSTNAME="--hostname-override=k8s-node-1" # location of the api-server KUBELET_API_SERVER="--api-servers=http://k8s-master:8080" # pod infrastructure container KUBELET_POD_INFRA_CONTAINER="--pod-infra-container-image=registry.access.redhat.com/rhel7/pod-infrastructure:latest" # Add your own! #KUBELET_ARGS="" KUBELET_ARGS="--cluster-dns=10.254.10.2 --cluster-domain=cluster.local. --allow-privileged=true" [root@k8s-node-1 ~]# systemctl restart kubelet.service
2.2修改APIserver
修改以下紅色部分:
[root@k8s-master ~]# cat /etc/kubernetes/apiserver ### # kubernetes system config # # The following values are used to configure the kube-apiserver # # The address on the local server to listen to. KUBE_API_ADDRESS="--insecure-bind-address=0.0.0.0" # The port on the local server to listen on. KUBE_API_PORT="--port=8080" # Port minions listen on # KUBELET_PORT="--kubelet-port=10250" # Comma separated list of nodes in the etcd cluster KUBE_ETCD_SERVERS="--etcd-servers=http://etcd:2379" # Address range to use for services KUBE_SERVICE_ADDRESSES="--service-cluster-ip-range=10.254.0.0/16" # default admission control policies KUBE_ADMISSION_CONTROL="--admission-control=NamespaceLifecycle,NamespaceExists,LimitRanger,SecurityContextDeny,ResourceQuota" # Add your own! KUBE_API_ARGS=""
2.3 修改yaml檔案
修改以下紅色部分:
[root@k8s-master dns14]# cat kube-dns-rc_14.yaml apiVersion: v1 kind: ReplicationController metadata: name: kube-dns-v20 namespace: kube-system labels: k8s-app: kube-dns version: v20 kubernetes.io/cluster-service: "true" spec: replicas: 1 selector: k8s-app: kube-dns version: v20 template: metadata: labels: k8s-app: kube-dns version: v20 annotations: scheduler.alpha.kubernetes.io/critical-pod: '' scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]' spec: containers: - name: kubedns image: gcr.io/google_containers/kubedns-amd64:1.8 imagePullPolicy: IfNotPresent 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: /healthz-kubedns port: 8080 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: # command = "/kube-dns" - --domain=cluster.local. - --dns-port=10053 - --kube-master-url=http://10.0.251.148:8080 ports: - containerPort: 10053 name: dns-local protocol: UDP - containerPort: 10053 name: dns-tcp-local protocol: TCP - name: dnsmasq image: gcr.io/google_containers/kube-dnsmasq-amd64:1.4.1 imagePullPolicy: IfNotPresent livenessProbe: httpGet: path: /healthz-dnsmasq port: 8080 scheme: HTTP initialDelaySeconds: 60 timeoutSeconds: 5 successThreshold: 1 failureThreshold: 5 args: - --cache-size=1000 - --no-resolv - --server=127.0.0.1#10053 - --log-facility=- ports: - containerPort: 53 name: dns protocol: UDP - containerPort: 53 name: dns-tcp protocol: TCP - name: healthz image: gcr.io/google_containers/exechealthz-amd64:1.2 imagePullPolicy: IfNotPresent resources: limits: memory: 50Mi requests: cpu: 10m # Note that this container shouldn't really need 50Mi of memory. The # limits are set higher than expected pending investigation on #29688. # The extra memory was stolen from the kubedns container to keep the # net memory requested by the pod constant. memory: 50Mi args: - --cmd=nslookup kubernetes.default.svc.cluster.local. 127.0.0.1 >/dev/null - --url=/healthz-dnsmasq - --cmd=nslookup kubernetes.default.svc.cluster.local. 127.0.0.1:10053 >/dev/null - --url=/healthz-kubedns - --port=8080 - --quiet ports: - containerPort: 8080 protocol: TCP dnsPolicy: Default # Don't use cluster DNS. [root@k8s-master dns14]# cat kube-dns-svc_14.yaml apiVersion: v1 kind: Service metadata: name: kube-dns namespace: kube-system labels: k8s-app: kube-dns kubernetes.io/cluster-service: "true" kubernetes.io/name: "KubeDNS" spec: selector: k8s-app: kube-dns clusterIP: 10.254.10.2 ports: - name: dns port: 53 protocol: UDP - name: dns-tcp port: 53 protocol: TCP [root@k8s-master dns14]#
2.4 下載映象
docker pull gcr.io/google_containers/kubedns-amd64:1.8 docker pull gcr.io/google_containers/kube-dnsmasq-amd64:1.4.1 docker pull gcr.io/google_containers/exechealthz-amd64:1.2
3、啟動
[root@k8s-master dns14]# kubectl create -f kube-dns-rc_14.yaml replicationcontroller "kube-dns-v20" created [root@k8s-master dns14]# kubectl create -f kube-dns-svc_14.yaml service "kube-dns" created
4、驗證
注意,以下演示中的web-0與web-1是兩個“Named Pod”,是通過建立PetSet建立出來的Pod。詳細介紹請參見後續文章。
[root@k8s-master dns14]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE frontend-service-1988680557-xuysd 1/1 Running 0 3h 10.0.82.5 k8s-node-4 web-0 1/1 Running 0 3h 10.0.28.3 k8s-node-1 web-1 1/1 Running 0 3h 10.0.82.6 k8s-node-4 [root@k8s-master dns14]# kubectl get svc mysql-service NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE mysql-service 10.254.194.71 <nodes> 3306/TCP 4h [root@k8s-master dns14]# kubectl exec -ti frontend-service-1988680557-xuysd /bin/bash [root@frontend-service-1988680557-xuysd /]# nslookup web-0.nginx Server: 10.254.10.2 Address: 10.254.10.2#53 Name: web-0.nginx.default.svc.cluster.local Address: 10.0.28.3 [root@frontend-service-1988680557-xuysd /]# nslookup web-1.nginx Server: 10.254.10.2 Address: 10.254.10.2#53 Name: web-1.nginx.default.svc.cluster.local Address: 10.0.82.6 [root@frontend-service-1988680557-xuysd /]# nslookup web-1.nginx.default.svc.cluster.local Server: 10.254.10.2 Address: 10.254.10.2#53 Non-authoritative answer: Name: web-1.nginx.default.svc.cluster.local Address: 10.0.82.6 [root@frontend-service-1988680557-xuysd /]# nslookup mysql-service Server: 10.254.10.2 Address: 10.254.10.2#53 Name: mysql-service.default.svc.cluster.local Address: 10.254.194.71