Kubernetes 1.2中的Kubernetes DNS失败 [英] Kubernetes DNS fails in Kubernetes 1.2

问题描述

我试图在Centos 7上的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。第一个适用于支持的kubernetes集群设置，并且涉及设置环境变量：

I'm attempting to set up DNS support in Kubernetes 1.2 on Centos 7. According to the documentation, there's two ways to do this. The first applies to a "supported kubernetes cluster setup" and involves setting environment variables:

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，所以我没有支持的kubernetes群集设置（这是什么？），还是有其他的需要设置其环境。

I added these settings to /etc/kubernetes/config and rebooted, with no effect, so either I don't have a supported kubernetes cluster setup (what's that?), or there's something else required to set its environment.

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

The second approach requires more manual setup. It adds two flags to kubelets, which I set by updating /etc/kubernetes/kubelet to include:

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

并重新启动kubelet与 systemctl restart kubelet 。那么就需要启动复制控制器和服务。上面提到的doc页面提供了一些需要编辑的模板文件，无论是本地更改（我的Kubernetes API服务器都是监听主机名的实际IP地址而不是127.0.0.1，因此需要添加一个 - kube-master-url设置）并删除一些Salt依赖项。当我这样做，复制控制器成功启动四个容器，但kube2sky容器在完成初始化后大约一分钟终止：

and restarting the kubelet with systemctl restart kubelet. Then it's necessary to start a replication controller and a service. The doc page cited above provides a couple of template files for this that require some editing, both for local changes (my Kubernetes API server listens to the actual IP address of the hostname rather than 127.0.0.1, making it necessary to add a --kube-master-url setting) and to remove some Salt dependencies. When I do this, the replication controller starts four containers successfully, but the kube2sky container gets terminated about a minute after completing initialization:

[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

I已经确定终止是由healthz容器报告后完成的：

I've determined that the termination is done by the healthz container after reporting:

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正常。但是，有一个异常：在创建复制控制器时需要指定--validate = false，否则命令将获取消息：

Aside from this, all other logs look normal. However, there is one anomaly: it was necessary to specify --validate=false when creating the replication controller, as the command otherwise gets the message:

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

将验证关闭？这些论据来自于Kubernetes文档。如果没有，需要什么来获得这个运行？

Could this be related? These arguments come directly Kubernetes documentation. if not, what's needed to get this running?

我使用的是skydns-rc.yaml：

Here is the skydns-rc.yaml I used:

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skydns-svc.yaml：

and skydns-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

推荐答案

我刚刚评论了包含 successThreshold 和 failureThreshold 值在 skydns-rc.yaml 中，然后重新运行kubectl命令。

I just commented out the lines that contain the successThreshold and failureThreshold values in skydns-rc.yaml, then re-run the kubectl commands.

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

这篇关于Kubernetes 1.2中的Kubernetes DNS失败的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！