DNS部署

DNS部署

基於上一篇文章從零開始搭建基於calico的kubenetes，已經完成了kubernetes的部署。但未部署DNS。本章節將介紹DNS部署。

配置文件準備

skydns-rc.yaml 注意此文件與kubernetes官方提供的模板相比，在此mount了從節點的配置文件/etc/kubernetes/worker-kubeconfig.yaml,原因在於DNS部署有時候會出現很多未知的錯誤，如：10.100.0.1:443鏈接被拒絕、或者證書加載錯誤等:

# 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.

# TODO - At some point, we need to rename all skydns-*.yaml.* files to kubedns-*.yaml.*

# Warning: This is a file generated from the base underscore template file: skydns-rc.yaml.base

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: shenshouer/kubedns-amd64:1.8
        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=https://172.18.8.101
        - --kubecfg-file=/etc/kubernetes/worker-kubeconfig.yaml
        - --federations=myfederation=federation.test
        ports:
        - containerPort: 10053
          name: dns-local
          protocol: UDP
        - containerPort: 10053
          name: dns-tcp-local
          protocol: TCP
        volumeMounts:
          - mountPath: /etc/ssl/certs
            name: "ssl-certs"
          - mountPath: /etc/kubernetes/worker-kubeconfig.yaml
            name: "kubeconfig"
            readOnly: true
          - mountPath: /etc/kubernetes/ssl
            name: "etc-kube-ssl"
            readOnly: true

      - name: dnsmasq
        image: shenshouer/kube-dnsmasq-amd64:1.4
        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: shenshouer/exechealthz-amd64:1.2
        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.
      volumes:
        - name: "ssl-certs"
          hostPath:
            path: "/usr/share/ca-certificates"
        - name: "kubeconfig"
          hostPath:
            path: "/etc/kubernetes/worker-kubeconfig.yaml"
        - name: "etc-kube-ssl"
          hostPath:
            path: "/etc/kubernetes/ssl"

skydns-svc.yaml與官方模板相同:

# 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.

# TODO - At some point, we need to rename all skydns-*.yaml.* files to kubedns-*.yaml.*

# Warning: This is a file generated from the base underscore template file: skydns-svc.yaml.base

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: 172.30.0.10
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP

部署

將skydns-svc.yaml與skydns-rc.yaml文件放置到master主機上的一個文件夾內,本次示例中爲/root/dns/

cd /root/dns
kubectl create -f ./

檢查

• 檢查pod、rc、svc, 如下狀態爲正常

root@ubuntu-01:~/dns# kubectl get po -o wide --namespace kube-system
NAME                 READY     STATUS    RESTARTS   AGE       IP               NODE
kube-dns-v20-rqt9w   3/3       Running   0          50m       192.168.31.209   172.18.8.102

root@ubuntu-01:~/dns# kubectl get rc --namespace kube-system
NAME           DESIRED   CURRENT   READY     AGE
kube-dns-v20   1         1         1         51m

root@ubuntu-01:~/dns# kubectl get svc --namespace kube-system
NAME       CLUSTER-IP    EXTERNAL-IP   PORT(S)         AGE
kube-dns   172.30.0.10   <none>        53/UDP,53/TCP   51m

• 檢查dns解析是否正常：

先啓動一個輔助工具busybox.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  hostname: busybox-1
  subdomain: default
  containers:
  - image: busybox
    command:
      - sleep
      - "360000"
    name: busybox

並等待此pod啓動：

root@ubuntu-01:~# kubectl get po
NAME                      READY     STATUS    RESTARTS   AGE
busybox                   1/1       Running   0          52m
kube-proxy-172.18.8.102   1/1       Running   0          56m
kube-proxy-172.18.8.103   1/1       Running   0          56m

使用busybox檢查域名kubernetes解析情況

root@ubuntu-01:~# kubectl exec -it busybox -- nslookup kubernetes
Server:    10.100.0.10
Address 1: 10.100.0.10 kube-dns.kube-system.svc.cluster.local

Name:      kubernetes
Address 1: 10.100.0.1 kubernetes.default.svc.cluster.local

域名kubernetes正常解析至10.100.0.1與服務中一致，表明DNS部署成功.

root@ubuntu-01:~# kubectl get svc
NAME         CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   10.100.0.1   <none>        443/TCP   1h