external-dns 阿里云容器服务实战

受Kubernetes的集群内部DNS服务器Kubernetes DNS的启发，ExternalDNS使Kubernetes资源可通过公共DNS服务器配置与发布。 与KubeDNS一样，它从Kubernetes API中检索资源列表（Service，Ingress等），以确定所需的DNS记录列表。 然而，与KubeDNS不同，它本身不是DNS服务器，而是仅相应地配置其他DNS提供商 - 例如， Alibaba Cloud 或其他服务商。

配置 RAM 信息

首先在阿里云容器服务创建一个Kubernetes 集群，选择节点列表内任意一个Worker节点，打开对应的节点列表信息页面。

寻找到对应的 RAM 角色，打开ram 控制台 https://ram.console.aliyun.com/#/role/list，找到对应的角色管理。

选择管理 -> 角色授权策略 -> 查看权限 -> 修改授权策略
添加以下权限

 {
      "Action": "alidns:AddDomainRecord",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "alidns:DeleteDomainRecord",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "alidns:UpdateDomainRecord",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "alidns:DescribeDomainRecords",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "alidns:DescribeDomains",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "pvtz:AddZoneRecord",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "pvtz:DeleteZoneRecord",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "pvtz:UpdateZoneRecord",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "pvtz:DescribeZoneRecords",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "pvtz:DescribeZones",
      "Resource": "*",
      "Effect": "Allow"
    },
    {
      "Action": "pvtz:DescribeZoneInfo",
      "Resource": "*",
      "Effect": "Allow"
    }

部署External-DNS

配置完毕RAM后，就可以部署External-DNS，部署yaml如下:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: external-dns
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: external-dns
rules:
- apiGroups: [""]
  resources: ["services"]
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get","watch","list"]
- apiGroups: ["extensions"] 
  resources: ["ingresses"] 
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["nodes"]
  verbs: ["list","watch"]
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: external-dns-viewer
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: external-dns
subjects:
- kind: ServiceAccount
  name: external-dns
  namespace: default
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: registry.cn-beijing.aliyuncs.com/xianlu/external-dns:v0.5.17-102-gc4bcada
        args:
        - --source=service
        - --source=ingress
        - --provider=alibabacloud
        - --policy=sync # enable full synchronization
        - --registry=txt
        - --txt-owner-id=my-identifier
        - --alibaba-cloud-config-file= # enable sts token 
        volumeMounts:
        - mountPath: /usr/share/zoneinfo
          name: hostpath
      volumes:
      - name: hostpath
        hostPath:
          path: /usr/share/zoneinfo
          type: Directory
          

使用External-DNS

我们以公有域名为例,Aliyun dns 控制台地址为https://dns.console.aliyun.com/#/dns/domainList，目前已经有一个域名托管。

下面我们创建一个Service测试一下

apiVersion: v1
kind: Service
metadata:
  name: nginx
  annotations:
    external-dns.alpha.kubernetes.io/hostname: nginx.xianlubird.top.
spec:
  type: LoadBalancer
  ports:
  - port: 80
    name: http
    targetPort: 80
  selector:
    app: nginx

---

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx
spec:
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 80
          name: http

请注意这个annotation external-dns.alpha.kubernetes.io/hostname: nginx.xianlubird.top. 这里就是用来配置你想要挂载的 DNS 名称。External-dns会自动帮你将 IP 对应的 DNS 记录建立好。稍等片刻就能看到结果。

[root@izwz9dn4v9m0fowyqhbwhvz ~]# curl nginx.xianlubird.top
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

可以看到，这里域名已经可以正常访问了。 如果删除对应的Service ，对应的 DNS 解析记录也会被删除。

使用私有域名

阿里云 DNS 提供PrivateZone功能，可以针对特定的 VPC 使用私有域名解析，如果想使用私有域名解析，请修改external-dns 配置

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: registry.cn-beijing.aliyuncs.com/xianlu/external-dns:v0.5.17-102-gc4bcada
        args:
        - --source=service
        - --source=ingress
        - --provider=alibabacloud
        - --policy=sync # enable full synchronization
        - --registry=txt
        - --txt-owner-id=my-identifier
        - --alibaba-cloud-zone-type=private
        - --alibaba-cloud-config-file= # enable sts token 
        volumeMounts:
        - mountPath: /usr/share/zoneinfo
          name: hostpath
      volumes:
      - name: hostpath
        hostPath:
          path: /usr/share/zoneinfo
          type: Directory
          

注意 - --alibaba-cloud-zone-type=private 这里指定了zone 类型为私有，这样就可以监控私有域名的解析。

以下面的例子说明

apiVersion: v1
kind: Service
metadata:
  name: nginx
  annotations:
    external-dns.alpha.kubernetes.io/hostname: ingress-sg2.sg.private.local.
spec:
  type: LoadBalancer
  ports:
  - port: 80
    name: http
    targetPort: 80
  selector:
    app: nginx

---

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx
spec:
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 80
          name: http

这里希望将这个Service 注册到ingress-sg2.sg.private.local.域名下，首先在阿里云DNS privatezone 里面创建根域名private.local

请注意，一定要先关联 VPC，否则无法添加记录，您可以先手动添加一个无效记录，然后绑定对应的 VPC。

配置完毕后，external-dns 就可以自动帮助域名注册

使用子域名

如果使用阿里云DNS托管子域名，那么在部署external-dns 的时候就需要指定监听的子域名名称，这里我们以ack.dns-example.xyz
为例。

在部署external-dns的时候，需要使用一下模板

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: registry.cn-beijing.aliyuncs.com/xianlu/external-dns:v0.5.17-102-gc4bcada
        args:
        - --source=service
        - --source=ingress
        - --domain-filter=ack.dns-example.xyz
        - --provider=alibabacloud
        - --policy=sync # enable full synchronization
        - --registry=txt
        - --txt-owner-id=my-identifier
        - --alibaba-cloud-config-file= # enable sts token
        volumeMounts:
        - mountPath: /usr/share/zoneinfo
          name: hostpath
      volumes:
      - name: hostpath
        hostPath:
          path: /usr/share/zoneinfo
          type: Directory

这里请注意，一个巨大的区别点就在于- --domain-filter=ack.dns-example.xyz，这里的意思是，指定监听哪个域名domain。部署完毕后，我们创建一个例子看一下：

apiVersion: v1
kind: Service
metadata:
  name: nginx
  annotations:
    external-dns.alpha.kubernetes.io/hostname: nginx.ack.dns-example.xyz.
spec:
  type: LoadBalancer
  ports:
  - port: 80
    name: http
    targetPort: 80
  selector:
    app: nginx

---

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx
spec:
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 80
          name: http

可以看到域名已经成功解析

目前External-DNS 已经开源，项目地址： https://github.com/kubernetes-incubator/external-dns/blob/master/docs/tutorials/alibabacloud.md
更多参数详情，可以参考。