使用ExternalDNS自动化DNS配置

Kubernetes社区的生态繁荣和该领域技术的快速茁壮发展，已经是众所周知。Kubernetes领域有太多强大的、创新的技术产品，而最近引起我注意的项目是ExternalDNS。这是在近期的POC期间客户主动咨询起来的，我承诺客户会尝试一下ExternalDNS子项目，且使用后发现它真的令人印象深刻。 ExternalDNS子项目 ExternalDNS子项目（孵化器流程已被弃用...

RancherLabs

1859人浏览 · 2018-07-18 12:23:38

RancherLabs · 2018-07-18 12:23:38 发布

ExternalDNS子项目

ExternalDNS子项目（孵化器流程已被弃用）是由sig-network赞助并由Tim Hockin倡导的，旨在自动配置云DNS提供商。这很重要，因为它进一步支持基础架构自动化，用户可以在应用程序部署的同时直接完成DNS配置。

传统企业部署模型，通常是由多个孤立业务单元，来处理部署过程的不同部分。但带有ExternalDNS的Kubernetes不同于传统企业部署模型，它可以自动完成此过程的这一部分工作。有时候有可能会出现这种不好的情况：一部分软件已准备就绪，但它却必须等待另一个业务部门手动配置DNS。而有了ExternalDNS，这一潜在问题就被解决了。

通过ExternalDNS，组织团队可实现自动化和共同责任协作，而这将避免手动配置的错误，并使各方都能够更有效地将其产品推向市场。

AKS上的ExternalDNS配置和部署

我曾作为软件开发人员在.NET领域有过多年的工作经验。微软开发人员社区在我心中一直有一个特殊的位置，过去几年以来我参加过不少费城地区的Azure用户meetup，分享如何通过ACS（Azure Container Service）和AKS（Azure Kubernetes Service）使用Kubernetes on Azure。恰巧的是，向我咨询ExternalDNS的用户也正是在选择了Azure作为其IaaS产品。

下文是我准备的在AKS集群上启动ExternalDNS的分步说明和帮助程序代码。即使您使用的是其他公有云上的托管的Kubernetes，本教程依然适用。

先决条件

登录Azure AD，必要情况下请设置订阅。

几点注意事项

1、请注意，本文档中的外部模板文件使用了许多可选设置。

2、它也在debug级别日志中，因此您也可以自行进行troubleshooting。

在Azure AKS或Azure IaaS上设置ExternalDNS

1、创建Azure DNS记录

RESOURCE_GROUP=MC_rancher-group_c-6vkts_eastus
DNS_ZONE=vanbrackel.net
az network dns zone create -g $RESOURCE_GROUP -n $DNS_ZONE

2、根据您的注册商的需要委派DNS

3、创建服务主体以代表Kubernetes行事。

SUBSCRIPTION_ID="$(az account show | jq '.id')" && SUBSCRIPTION_ID=${SUBSCRIPTION_ID//\"}
TENANT_ID=$(az account show | jq '.tenantId') && TENANT_ID=${TENANT_ID//\"}
SCOPE=$(az group show --name $RESOURCE_GROUP | jq '.id') && SCOPE=${SCOPE//\"}
PRINCIPAL=$(az ad sp create-for-rbac --role="Contributor" --scopes=$SCOPE -n ExternalDnsServicePrincipal)
CLIENT_ID=$(echo $PRINCIPAL | jq '.appId') && CLIENT_ID=${CLIENT_ID//\"}
CLIENT_SECRET=$(echo $PRINCIPAL | jq '.password') && CLIENT_SECRET=${CLIENT_SECRET//\"}

4、创建你的云提供商配置。

echo "{ \"tenantId\": \"$TENANT_ID\", \"subscriptionId\": \"$SUBSCRIPTION_ID\", \"aadClientId\": \"$CLIENT_ID\", \"aadClientSecret\": \"$CLIENT_SECRET\", \"resourceGroup\": \"$RESOURCE_GROUP\"}" >> azure.json

5、使用云提供商配置来创建一个Kubernetes秘钥。

> kubectl create secret generic azure-config-file --from-file=azure.json
secret "azure-config-file" created

6、如果你使用的是Rancher配置的Azure IaaS Backed Clusters，从集群中删除ingress controller。

> kubectl get ns
NAME            STATUS    AGE
cattle-system   Active    1d
default         Active    1d
ingress-nginx   Active    1d
kube-public     Active    1d
kube-system     Active    1d
> kubectl delete ns/ingress-nginx
namespace "ingress-nginx" deleted

注意：如果您是使用Rancher中的 AKS配置的集群，则不会提供ingress controller。

7、安装nginx ingress controller并为ExternalDNS配置它。创建ingress-nginx部署和服务。

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/mandatory.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/provider/cloud-generic.yaml

8、由于在基于Rancher的Kubernetes集群上默认启用了RBAC，因此可以从下面的脚本创建名为externaldns.yaml的yaml文件，或者使用此repo中的externaldns-template.yaml文件。

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"]
---
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.opensource.zalan.do/teapot/external-dns:v0.5.2
        args:
        - --source=service
        - --source=ingress
        - --domain-filter=vanbrackel.net # (optional) limit to only vanbrackel.net domains; change to match the zone created above.
        - --provider=azure
        - --azure-resource-group=MC_rancher-group_c-6vkts_eastus # (optional) use the DNS zones from above
        volumeMounts:
        - name: azure-config-file
          mountPath: /etc/kubernetes
          readOnly: true
      volumes:
      - name: azure-config-file
        secret:
          secretName: azure-config-file

EXTERNAL_DNS=$(cat externaldns-template.yaml)
EXTERNAL_DNS=${EXTERNAL_DNS//DOMAIN/$DOMAIN} && echo "${EXTERNAL_DNS//RESOURCE_GROUP/$RESOURCE_GROUP}" >> externaldns.yaml
kubectl create -f externaldns.yaml

验证

1、以与部署ExternalDNS相同的方式在ingress中创建nginx服务

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx
spec:
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-svc
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: nginx
  type: ClusterIP
  
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: nginx
  annotations:
    kubernetes.io/ingress.class: nginx
spec:
  rules:
  - host: server.vanbrackel.net
    http:
      paths:
      - backend:
          serviceName: nginx-svc
          servicePort: 80
        path: /

NGINX=$(cat nginx-ingress-test-template.yaml) && echo "${NGINX//DOMAIN/$DOMAIN}" >> nginx-ingress-test.yaml

2、创建nginx-ingress controller

kubectl create -f nginx-ingress-test.yaml

3、稍等几分钟

4、检查一下是否已有record被创建出来

[jason@vblinux ~ ]$ az network dns record-set a list --resource-group $RESOURCE_GROUP --zone-name $DNS_ZONE
[
  {
    "arecords": [
      {
        "ipv4Address": "13.68.138.206"
      }
    ],
    "etag": "0fb3eaf9-7bf2-48c4-b8f8-432e05dce94a",
    "fqdn": "server.vanbrackel.net.",
    "id": "/subscriptions/c7e23d24-5dcd-4c7c-ae84-22f6f814dc02/resourceGroups/mc_rancher-group_c-6vkts_eastus/providers/Microsoft.Network/dnszones/vanbrackel.net/A/server",
    "metadata": null,
    "name": "server",
    "resourceGroup": "mc_rancher-group_c-6vkts_eastus",
    "ttl": 300,
    "type": "Microsoft.Network/dnszones/A"
  }
]

5、检查日志

kubectl logs external-dns-655df89959-7ztm2 
time="2018-06-13T23:57:11Z" level=info msg="config: {Master: KubeConfig: Sources:[service ingress] Namespace: AnnotationFilter: FQDNTemplate: CombineFQDNAndAnnotation:false Compatibility: PublishInternal:false ConnectorSourceServer:localhost:8080 Provider:azure GoogleProject: DomainFilter:[vanbrackel.net] ZoneIDFilter:[] AWSZoneType: AWSAssumeRole: AzureConfigFile:/etc/kubernetes/azure.json AzureResourceGroup:MC_rancher-group_c-6vkts_eastus CloudflareProxied:false InfobloxGridHost: InfobloxWapiPort:443 InfobloxWapiUsername:admin InfobloxWapiPassword: InfobloxWapiVersion:2.3.1 InfobloxSSLVerify:true DynCustomerName: DynUsername: DynPassword: DynMinTTLSeconds:0 InMemoryZones:[] PDNSServer:http://localhost:8081 PDNSAPIKey: Policy:sync Registry:txt TXTOwnerID:default TXTPrefix: Interval:1m0s Once:false DryRun:false LogFormat:text MetricsAddress::7979 LogLevel:debug}"
time="2018-06-13T23:57:11Z" level=info msg="Connected to cluster at https://10.0.0.1:443"
...
time="2018-06-14T00:02:11Z" level=debug msg="Retrieving Azure DNS zones."
time="2018-06-14T00:02:12Z" level=debug msg="Found 1 Azure DNS zone(s)."
time="2018-06-14T00:02:12Z" level=debug msg="Retrieving Azure DNS records for zone 'vanbrackel.net'."
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service default/kubernetes"
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service default/nginx-svc"
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service ingress-nginx/default-http-backend"
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service ingress-nginx/ingress-nginx"
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service kube-system/full-guppy-nginx-ingress-controller" time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service kube-system/full-guppy-nginx-ingress-default-backend"
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service kube-system/heapster"
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service kube-system/kube-dns"
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service kube-system/kubernetes-dashboard"
time="2018-06-14T00:02:12Z" level=debug msg="No endpoints could be generated from service kube-system/tiller-deploy"
time="2018-06-14T00:02:12Z" level=debug msg="Endpoints generated from ingress: default/nginx: [server.vanbrackel.net 0 IN A 13.68.138.206]"
time="2018-06-14T00:02:12Z" level=debug msg="Retrieving Azure DNS zones."
time="2018-06-14T00:02:12Z" level=debug msg="Found 1 Azure DNS zone(s)."
time="2018-06-14T00:02:12Z" level=info msg="Updating A record named 'server' to '13.68.138.206' for Azure DNS zone 'vanbrackel.net'."
time="2018-06-14T00:02:13Z" level=info msg="Updating TXT record named 'server' to '\"heritage=external-dns,external-dns/owner=default,external-dns/resource=ingress/default/nginx\"' for Azure DNS zone 'vanbrackel.net'."
time="2018-06-14T00:03:11Z" level=debug msg="Retrieving Azure DNS zones."
time="2018-06-14T00:03:12Z" level=debug msg="Found 1 Azure DNS zone(s)."
time="2018-06-14T00:03:12Z" level=debug msg="Retrieving Azure DNS records for zone 'vanbrackel.net'."
time="2018-06-14T00:03:12Z" level=debug msg="Found A record for 'server.vanbrackel.net' with target '13.68.138.206'."
time="2018-06-14T00:03:12Z" level=debug msg="Found TXT record for 'server.vanbrackel.net' with target '\"heritage=external-dns,external-dns/owner=default,external-dns/resource=ingress/default/nginx\"'."
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service default/kubernetes"
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service default/nginx-svc" time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service ingress-nginx/default-http-backend"
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service ingress-nginx/ingress-nginx"
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service kube-system/full-guppy-nginx-ingress-controller"
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service kube-system/full-guppy-nginx-ingress-default-backend"
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service kube-system/heapster"
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service kube-system/kube-dns"
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service kube-system/kubernetes-dashboard"
time="2018-06-14T00:03:12Z" level=debug msg="No endpoints could be generated from service kube-system/tiller-deploy"
time="2018-06-14T00:03:12Z" level=debug msg="Endpoints generated from ingress: default/nginx: [server.vanbrackel.net 0 IN A 13.68.138.206]"
time="2018-06-14T00:03:12Z" level=debug msg="Retrieving Azure DNS zones."
time="2018-06-14T00:03:12Z" level=debug msg="Found 1 Azure DNS zone(s)."

您还可以在ExternalDNS的repo中了解更多信息：

https://github.com/kubernetes-incubator/external-dns

如希望对原文中的代码有更深入的了解，请猛戳这里：

https://github.com/JasonvanBrackel/kubernetes-external-dns-in-rancher#prerequisites

微信号：RancherLabs

Cloudpods

开源、云原生的融合云平台

更多推荐

面向未来的 IT 基础设施管理架构——融合云（Unified IaaS）

随着数字化时代的到来，IT系统已成为人类社会正常运转不可或缺的组成部分。不远的未来，智能制造，5G和人工智能等技术将成为推动生产力发展的重要引擎，人类社会将面临前所未有的全面彻底的数字化浪潮。IT基础设施作为IT系统运行的平台和载体，是实现数字化的基石。在这场数字化浪潮中，企业必须积极拥抱云计算技术，采用符合技术发展趋势、面向未来的IT基础构架，才能在未来的竞争中赢得先机。一、云计算历经十余年

Cloudpods

使用Linux vfio将Nvidia GPU透传给QEMU虚拟机

Linux 上虚拟机 GPU 透传需要使用 vfio 的方式。主要是因为在 vfio 方式下对虚拟设备的权限和 DMA 隔离上做的更好。但是这么做也有个缺点，这个物理设备在主机和其他虚拟机都不能使用了。 qemu 直接使用物理设备本身命令行是很简单的，关键在于事先在主机上对系统、内核和物理设备的一些配置。单纯从 qemu 的命令行来看，其实和普通虚拟机启动就差了最后那个-device的选项。这

Cloudpods

Cloudpods负载均衡的功能介绍

作者:周有松今天的内容会从以下几个方面展开：负载均衡产品简介。主要介绍负载均衡作为一个云上产品，它的功能模型是怎样的，日常使用中会遇到的业务词汇负载均衡的功能与典型应用场景。这部分主要结合业务词汇，对负载均衡服务中常见的一些功能选项进行介绍，并举例介绍一些典型的应用场景最后，我们做一下总结，讨论一下负载均衡产品相比传统方式的优点一、产品简介 1. 以NGINX为例提到负载均衡，我们以