Kubernetes 1.5 配置dns

　　在kubernetes1.2的時候，採用了skydns + kube2dns +etcd的方式來部署dns。而從1.3開始，則部署方式有了一點兒變化，將skydns和kube2dns封裝到了一個容器鏡像中，放棄了etcd，而將dns解析直接放入到了內存之中，同時引入了dnsmasq，進一步利用其緩存，具體的原理，請查閱相關文檔。本篇文檔，主要闡述新版的dns在kubernetes中的具體部署。

　　在Kubernetes的源碼目錄中，有個cluster/addons/dns目錄，下面有幾個與dns相關的文件，咱們將其中的skydns-rc.yaml.sed以及skydns-svc.yaml.sed文件下載到本地，並去掉後綴。只是拷貝文件的話，能夠經過https://rawgit.com這個地址加速，以下：

wget https://rawgit.com/kubernetes/kubernetes/release-1.5/cluster/addons/dns/skydns-rc.yaml.sed -O skydns-rc.yaml
wget https://rawgit.com/kubernetes/kubernetes/release-1.5/cluster/addons/dns/skydns-svc.yaml.sed -O skydns-svc.yaml

下載下來的原文件是用於saltstack自動化安裝的，咱們手動處理的時候，須要進行相關修改。

修改skydns-rc.yaml內容以下：

# 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.

# TODO - At some point, we need to rename all skydns-*.yaml.* files to kubedns-*.yaml.*
# 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"
spec:
　#指定副本數
  replicas: 1
  # 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: ''
        scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
    spec:
      containers:
      - name: kubedns
　　　　　#修改image地址，默認是google的倉庫地址，若是不擔憂被牆，能夠直接使用，我這裏使用的私有倉庫地址，若是要使用國內其餘倉庫地址，推薦使用阿里雲鏡像庫
        image: myhub.fdccloud.com/library/kubedns-amd64:1.9
        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:
　　　　 # --domain指定一級域名，可自定義 - --domain=cluster.local.
        - --dns-port=10053
        - --config-map=kube-dns
　　　　 #增長--kube-master-url，指向kube master的地址 - --kube-master-url=http://10.5.10.116:8080
        # This should be set to v=2 only after the new image (cut from 1.5) has
        # been released, otherwise we will flood the logs.
        - --v=0
        #__PILLAR__FEDERATIONS__DOMAIN__MAP__
        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
      - name: dnsmasq
        image: myhub.fdccloud.com/library/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=-　　#註釋掉該行
        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: 10Mi
      - name: dnsmasq-metrics
        image: myhub.fdccloud.com/library/dnsmasq-metrics-amd64:1.0
        livenessProbe:
          httpGet:
            path: /metrics
            port: 10054
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        args:
        - --v=2
        - --logtostderr
        ports:
        - containerPort: 10054
          name: metrics
          protocol: TCP
        resources:
          requests:
            memory: 10Mi
      - name: healthz
        image: myhub.fdccloud.com/library/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.

修改skydns-svc.yaml內容以下：

# 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.

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

# __MACHINE_GENERATED_WARNING__

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
 #指定clusterIP，後面各pod的dns地址都會指向該地址   clusterIP: 10.254.0.100
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP

啓動dns：

kubectl create -f skydns-rc.yaml
kubectl create -f skydns-svc.yaml

修改各node節點上的/etc/kubernetes/kubelet配置文件，增長以下行：

KUBELET_ARGS="--cluster_dns=10.254.0.100 --cluster_domain=cluster.local"

重啓各節點：

systemctl restart kubelet

添加一個busybox的pod用於測試，busybox.yaml內容以下：

apiVersion: v1
kind: Pod
metadata:
  labels:
    name: busybox
    role: master
  name: busybox
spec:
  containers:
  - name: busybox
    image: myhub.fdccloud.com/library/busybox
    command:
    - sleep
    - "3600"

執行以下操做：

kubectl exec -it busybox sh
nslookup kubernetes
nslookup kubernetes.default.cluster.local
nslookup kubernetes.default.svc.cluster.local

若是能正常解析，則部署OK。