Kubernetes DNS在Kubernetes 1.2中失败

Question

我试图在Centos 7上在Kubernetes 1.2中设置DNS支持。根据文档，有两种方法可以做到这一点。第一个应用于“支持的kubernetes集群设置”，涉及设置环境变量：

ENABLE_CLUSTER_DNS="${KUBE_ENABLE_CLUSTER_DNS:-true}"
DNS_SERVER_IP="10.0.0.10"
DNS_DOMAIN="cluster.local"
DNS_REPLICAS=1

我将这些设置添加到/etc/ kubernetes /config并重新启动，没有任何效果，所以要么我没有受支持的kubernetes集群设置(这是什么？)，要么需要设置它的环境。

第二种方法需要更多的手动设置。它向kubelets添加了两个标志，我通过更新/etc/kubernetes/kubelet设置了这些旗帜，包括：

KUBELET_ARGS="--cluster-dns=10.0.0.10 --cluster-domain=cluster.local"

然后用systemctl restart kubelet重新启动kubelet。然后，有必要启动复制控制器和服务。上面引用的doc页面为此提供了几个模板文件，需要进行一些编辑，用于本地更改(我的Kubernetes API服务器侦听主机名的实际IP地址，而不是127.0.0.1，因此需要添加-kube-master-url设置)和删除一些盐依赖项。当我这样做时，复制控制器成功地启动了四个容器，但是kube2sky容器在完成初始化后大约一分钟就被终止了：

[david@centos dns]$ kubectl --server="http://centos:8080" --namespace="kube-system" logs -f kube-dns-v11-t7nlb -c kube2sky
I0325 20:58:18.516905       1 kube2sky.go:462] Etcd server found: http://127.0.0.1:4001
I0325 20:58:19.518337       1 kube2sky.go:529] Using http://192.168.87.159:8080 for kubernetes master
I0325 20:58:19.518364       1 kube2sky.go:530] Using kubernetes API v1
I0325 20:58:19.518468       1 kube2sky.go:598] Waiting for service: default/kubernetes
I0325 20:58:19.533597       1 kube2sky.go:660] Successfully added DNS record for Kubernetes service.
F0325 20:59:25.698507       1 kube2sky.go:625] Received signal terminated

在报告之后，我确定终止是由healthz容器完成的：

2016/03/25 21:00:35 Client ip 172.17.42.1:58939 requesting /healthz probe servicing cmd nslookup kubernetes.default.svc.cluster.local 127.0.0.1 >/dev/null
2016/03/25 21:00:35 Healthz probe error: Result of last exec: nslookup: can't resolve 'kubernetes.default.svc.cluster.local', at 2016-03-25 21:00:35.608106622 +0000 UTC, error exit status 1

除此之外，所有其他日志看起来都很正常。但是，有一个异常情况:在创建复制控制器时必须指定--false=false，否则命令将得到消息：

error validating "skydns-rc.yaml": error validating data: [found invalid field successThreshold for v1.Probe, found invalid field failureThreshold for v1.Probe]; if you choose to ignore these errors, turn validation off with --validate=false

这可能是相关的吗？这些论点直接来自Kubernetes的文档。如果没有，需要什么才能让它运行？

这是我用的天窗-rc.yaml

apiVersion: v1
kind: ReplicationController
metadata:
  name: kube-dns-v11
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    version: v11
    kubernetes.io/cluster-service: "true"
spec:
  replicas: 1
  selector:
    k8s-app: kube-dns
    version: v11
  template:
    metadata:
      labels:
        k8s-app: kube-dns
        version: v11
        kubernetes.io/cluster-service: "true"
    spec:
      containers:
      - name: etcd
        image: gcr.io/google_containers/etcd-amd64:2.2.1
        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:
            cpu: 100m
            memory: 500Mi
          requests:
            cpu: 100m
            memory: 50Mi
        command:
        - /usr/local/bin/etcd
        - -data-dir
        - /var/etcd/data
        - -listen-client-urls
        - http://127.0.0.1:2379,http://127.0.0.1:4001
        - -advertise-client-urls
        - http://127.0.0.1:2379,http://127.0.0.1:4001
        - -initial-cluster-token
        - skydns-etcd
        volumeMounts:
        - name: etcd-storage
          mountPath: /var/etcd/data
      - name: kube2sky
        image: gcr.io/google_containers/kube2sky:1.14
        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:
            cpu: 100m
            # Kube2sky watches all pods.
            memory: 200Mi
          requests:
            cpu: 100m
            memory: 50Mi
        livenessProbe:
          httpGet:
            path: /healthz
            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: 30
          timeoutSeconds: 5
        args:
        # command = "/kube2sky"
        - --domain="cluster.local"
        - --kube-master-url=http://192.168.87.159:8080
      - name: skydns
        image: gcr.io/google_containers/skydns:2015-10-13-8c72f8c
        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:
            cpu: 100m
            memory: 200Mi
          requests:
            cpu: 100m
            memory: 50Mi
        args:
        # command = "/skydns"
        - -machines=http://127.0.0.1:4001
        - -addr=0.0.0.0:53
        - -ns-rotate=false
        - -domain="cluster.local"
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
      - name: healthz
        image: gcr.io/google_containers/exechealthz:1.0
        resources:
          # keep request = limit to keep this container in guaranteed class
          limits:
            cpu: 10m
            memory: 20Mi
          requests:
            cpu: 10m
            memory: 20Mi
        args:
        - -cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 >/dev/null
        - -port=8080
        ports:
        - containerPort: 8080
          protocol: TCP
      volumes:
      - name: etcd-storage
        emptyDir: {}
      dnsPolicy: Default  # Don't use cluster DNS.

和天空-svc.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:  "10.0.0.10"
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP

Answer 1

我只是注释掉了包含successThreshold和failureThreshold值的skydns-rc.yaml行，然后重新运行kubectl命令。

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