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）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 $DNS_ZONE2、根据您的注册商的需要委派DNS
3、创建服务主体以代表Kubernetes行事。
SUBSCRIPTION_ID="$(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.json5、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" created6、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.yaml8、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: v1kind: ServiceAccountmetadata:
name: external-dns---apiVersion: rbac.authorization.k8s.io/v1beta1kind: ClusterRolemetadata: name: external-dnsrules:
- 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/v1beta1kind: ClusterRoleBindingmetadata: name: external-dns-viewerroleRef:
apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: external-dnssubjects:
- kind: ServiceAccount name: external-dns namespace: default---apiVersion: extensions/v1beta1kind: Deploymentmetadata:
name: external-dnsspec:
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/v1beta1kind: Deploymentmetadata:
name: nginxspec:
template:
metadata:
labels:
app: nginx spec:
containers:
- image: nginx name: nginx ports:
- containerPort: 80---apiVersion: v1kind: Servicemetadata:
name: nginx-svcspec:
ports:
- port: 80 protocol: TCP targetPort: 80 selector:
app: nginx type: ClusterIP
---apiVersion: extensions/v1beta1kind: Ingressmetadata:
name: nginx annotations:
kubernetes.io/ingress.class: nginxspec:
rules:
- host: server.vanbrackel.net http:
paths:
- backend:
serviceName: nginx-svc servicePort: 80 path: /
NGINX=$(cat nginx-ingress-test-template.yaml) && echo "${NGINX//DOMAIN/$DOMAIN}" >> nginx-ingress-test.yaml2、创建nginx-ingress controller
kubectl create -f nginx-ingress-test.yaml3、稍等几分钟
4、检查一下是否已有record被创建出来
[jason@vblinux ~ ]$ 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
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/69946831/viewspace-3156343/ ，如需转载，请注明出处，否则将追究法律责任。
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