Setting up ExternalDNS for Services on Alibaba Cloud¶
This tutorial describes how to setup ExternalDNS for usage within a Kubernetes cluster on Alibaba Cloud. Make sure to use >=0.5.6 version of ExternalDNS for this tutorial
RAM Permissions¶
{
"Version": "1",
"Statement": [
{
"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"
}
]
}
When running on Alibaba Cloud, you need to make sure that your nodes (on which External DNS runs) have the RAM instance profile with the above RAM role assigned.
Set up a Alibaba Cloud DNS service or Private Zone service¶
Alibaba Cloud DNS Service is the domain name resolution and management service for public access. It routes access from end-users to the designated web app.
Alibaba Cloud Private Zone is the domain name resolution and management service for VPC internal access.
If you prefer to try-out ExternalDNS in one of the existing domain or zone you can skip this step
Create a DNS domain which will contain the managed DNS records. For public DNS service, the domain name should be valid and owned by yourself.
Make a note of the ID of the hosted zone you just created.
$ aliyun alidns DescribeDomains --KeyWord="external-dns-test.com" | jq -r '.Domains.Domain[0].DomainId'
Deploy ExternalDNS¶
Connect your kubectl client to the cluster you want to test ExternalDNS with.
Then apply one of the following manifests file to deploy ExternalDNS.
Manifest (for clusters without RBAC enabled)¶
apiVersion: apps/v1
kind: Deployment
metadata:
name: external-dns
spec:
strategy:
type: Recreate
selector:
matchLabels:
app: external-dns
template:
metadata:
labels:
app: external-dns
spec:
containers:
- name: external-dns
image: k8s.gcr.io/external-dns/external-dns:v0.7.6
args:
- --source=service
- --source=ingress
- --domain-filter=external-dns-test.com # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
- --provider=alibabacloud
- --policy=upsert-only # would prevent ExternalDNS from deleting any records, omit to enable full synchronization
- --alibaba-cloud-zone-type=public # only look at public hosted zones (valid values are public, private or no value for both)
- --registry=txt
- --txt-owner-id=my-identifier
volumeMounts:
- mountPath: /usr/share/zoneinfo
name: hostpath
volumes:
- name: hostpath
hostPath:
path: /usr/share/zoneinfo
type: Directory
Manifest (for clusters with RBAC enabled)¶
apiVersion: v1
kind: ServiceAccount
metadata:
name: external-dns
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
name: external-dns
rules:
- apiGroups: [""]
resources: ["services","endpoints","pods"]
verbs: ["get","watch","list"]
- apiGroups: ["extensions","networking.k8s.io"]
resources: ["ingresses"]
verbs: ["get","watch","list"]
- apiGroups: [""]
resources: ["nodes"]
verbs: ["list"]
---
apiVersion: rbac.authorization.k8s.io/v1
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: apps/v1
kind: Deployment
metadata:
name: external-dns
spec:
strategy:
type: Recreate
selector:
matchLabels:
app: external-dns
template:
metadata:
labels:
app: external-dns
spec:
serviceAccountName: external-dns
containers:
- name: external-dns
image: k8s.gcr.io/external-dns/external-dns:v0.7.6
args:
- --source=service
- --source=ingress
- --domain-filter=external-dns-test.com # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
- --provider=alibabacloud
- --policy=upsert-only # would prevent ExternalDNS from deleting any records, omit to enable full synchronization
- --alibaba-cloud-zone-type=public # only look at public hosted zones (valid values are public, private or no value for both)
- --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
Arguments¶
This list is not the full list, but a few arguments that where chosen.
alibaba-cloud-zone-type¶
alibaba-cloud-zone-type allows filtering for private and public zones
- If value is
public, it will sync with records in Alibaba Cloud DNS Service - If value is
private, it will sync with records in Alibaba Cloud Private Zone Service
Verify ExternalDNS works (Ingress example)¶
Create an ingress resource manifest file.
For ingress objects ExternalDNS will create a DNS record based on the host specified for the ingress object.
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: foo
annotations:
kubernetes.io/ingress.class: "nginx" # use the one that corresponds to your ingress controller.
spec:
rules:
- host: foo.external-dns-test.com
http:
paths:
- backend:
service:
name: foo
port:
number: 80
pathType: Prefix
Verify ExternalDNS works (Service example)¶
Create the following sample application to test that ExternalDNS works.
For services ExternalDNS will look for the annotation
external-dns.alpha.kubernetes.io/hostnameon the service and use the corresponding value.
apiVersion: v1
kind: Service
metadata:
name: nginx
annotations:
external-dns.alpha.kubernetes.io/hostname: nginx.external-dns-test.com.
spec:
type: LoadBalancer
ports:
- port: 80
name: http
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx
spec:
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
name: http
After roughly two minutes check that a corresponding DNS record for your service was created.
$ aliyun alidns DescribeDomainRecords --DomainName=external-dns-test.com
{
"PageNumber": 1,
"TotalCount": 1,
"PageSize": 20,
"RequestId": "1DBEF426-F771-46C7-9802-4989E9C94EE8",
"DomainRecords": {
"Record": [
{
"RR": "nginx",
"Status": "ENABLE",
"Value": "1.2.3.4",
"Weight": 1,
"RecordId": "3994015629411328",
"Type": "A",
"DomainName": "external-dns-test.com",
"Locked": false,
"Line": "default",
"TTL": 600
}，
{
"RR": "nginx",
"Status": "ENABLE",
"Value": "heritage=external-dns;external-dns/owner=my-identifier",
"Weight": 1,
"RecordId": "3994015629411329",
"Type": "TTL",
"DomainName": "external-dns-test.com",
"Locked": false,
"Line": "default",
"TTL": 600
}
]
}
}
Note created TXT record alongside ALIAS record. TXT record signifies that the corresponding ALIAS record is managed by ExternalDNS. This makes ExternalDNS safe for running in environments where there are other records managed via other means.
Let’s check that we can resolve this DNS name. We’ll ask the nameservers assigned to your zone first.
If you hooked up your DNS zone with its parent zone correctly you can use curl to access your site.
$ curl nginx.external-dns-test.com.
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
...
</head>
<body>
...
</body>
</html>
Custom TTL¶
The default DNS record TTL (Time-To-Live) is 300 seconds. You can customize this value by setting the annotation external-dns.alpha.kubernetes.io/ttl.
e.g., modify the service manifest YAML file above:
apiVersion: v1
kind: Service
metadata:
name: nginx
annotations:
external-dns.alpha.kubernetes.io/hostname: nginx.external-dns-test.com
external-dns.alpha.kubernetes.io/ttl: 60
spec:
...
This will set the DNS record’s TTL to 60 seconds.
Clean up¶
Make sure to delete all Service objects before terminating the cluster so all load balancers get cleaned up correctly.
Give ExternalDNS some time to clean up the DNS records for you. Then delete the hosted zone if you created one for the testing purpose.
For more info about Alibaba Cloud external dns, please refer this docs