kubernetes - 如何在Kubernetes 1.14版上启用coredns进行DNS查找？

Question

我在 ubuntu仿生的 kubernetes 1.14 版本中发现服务(DNS)时遇到问题。
现在，我的两个Pod正在使用IP地址进行通信。如何启用 coredns 进行服务(DNS)发现？
这是kube-system namespace 中用于服务和pod的kubectl的输出:

    kubectl get pods,svc --namespace=kube-system | grep dns
    pod/coredns-fb8b8dccf-6plz2          1/1     Running            0          6d23h
    pod/coredns-fb8b8dccf-thxh6          1/1     Running            0          6d23h
    
    service/kube-dns        ClusterIP   10.96.0.10       <none>        53/UDP,53/TCP,9153/TCP   6d23h

我已经使用以下步骤在主节点(ubuntu仿生机器)上安装了kubernetes

    apt-get update
    apt-get install     apt-transport-https     ca-certificates     curl     gnupg-agent     software-properties-common
    curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add -
    add-apt-repository    "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
    apt-get update
    apt-get install docker-ce docker-ce-cli containerd.io
    apt-get update && apt-get install -y apt-transport-https curl
    curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
    
    cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
    deb https://apt.kubernetes.io/ kubernetes-xenial main
    EOF
    
    apt-get update
    apt-get install -y kubelet kubeadm kubectl
    kubectl version
    apt-mark hold kubelet kubeadm kubectl
    kubeadm config images pull
    swapoff -a
    kubeadm init
    
    mkdir -p $HOME/.kube
    cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
    chown $(id -u):$(id -g) $HOME/.kube/config
    sysctl net.bridge.bridge-nf-call-iptables=1
    kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"
    kubectl get pods --all-namespaces

这是在工作节点上

    Docker is already installed, so directly installing kubernetes on worker node
    apt-get update && apt-get install -y apt-transport-https curl
    curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
    cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
    deb https://apt.kubernetes.io/ kubernetes-xenial main
    EOF
    
    apt-get update
    apt-get install -y kubelet kubeadm kubectl
    kubectl version
    apt-mark hold kubelet kubeadm kubectl
    swapoff -a
    Now joined worker node to master

回答:-
我认为默认情况下所有设置都正确设置，我有一个误解，就是我可以使用规范中指定的容器名称和端口来调用从另一个容器运行在另一个容器中的服务器，而应该使用服务名称和端口。
以下是我的部署规范和服务规范:-
部署规格:

    apiVersion: extensions/v1beta1
    kind: Deployment
    metadata:
      name: node-server1-deployment
    spec:
      replicas: 1
      template:
    metadata:
      labels:
        app: node-server1
    spec:
      hostname: node-server1
      containers:
      - name: node-server1
        image: bvenkatr/node-server1:1
        ports:
        - containerPort: 5551

服务规格:

    kind: Service
    apiVersion: v1
    metadata:
      name: node-server1-service
    spec:
      selector:
         app: node-server1
      ports:
      - protocol: TCP
        port: 5551

Answer 1

As of Kubernetes v1.12, CoreDNS is the recommended DNS Server, replacing kube-dns. In Kubernetes, CoreDNS is installed with the following default Corefile configuration:

apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
data:
  Corefile: |
    .:53 {
        errors
        health
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           upstream
           fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        proxy . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }

您可以找到 here的更多信息。

您可以通过运行以下命令来验证环境:

kubectl get cm coredns -n kube-system -o yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system

和:
kubeadm配置 View
DNS:
类型:CoreDNS

在kubeadm初始化期间，您应该注意到:

[addons] Applied essential addon: CoreDNS

如果您要从kube-dns迁移到CoreDNS，请确保在升级期间将CoreDNS feature gate设置为 true 。例如，这是v1.11.0升级的样子: kubeadm upgrade apply v1.11.0 --feature-gates=CoreDNS=true

In Kubernetes version 1.13 and later the CoreDNS feature gate is removed and CoreDNS is used by default. More information here.

您可以通过运行以下命令来查看您的coredns pod是否正常运行:

kubectl logs <your coredns pod> -n kube-system
.:53
2019-05-02T13:32:41.438Z [INFO] CoreDNS-1.3.1
CoreDNS-1.3.1
.
.