Chapter 13. Tutorial: Deploying the External DNS Operator on ROSA

1. Configure the following environment variables:

   $ export DOMAIN=<apps.example.com> 1
   $ export AWS_PAGER=""
   $ export CLUSTER=$(oc get infrastructure cluster -o=jsonpath="{.status.infrastructureName}"  | sed 's/-[a-z0-9]\{5\}$//')
   $ export REGION=$(oc get infrastructure cluster -o=jsonpath="{.status.platformStatus.aws.region}")
   $ export AWS_ACCOUNT_ID=$(aws sts get-caller-identity --query Account --output text)
   $ export SCRATCH="/tmp/${CLUSTER}/external-dns"
   $ mkdir -p ${SCRATCH}

   1

   Replace with the custom domain you want to use for the IngressController.

2. Ensure all fields output correctly before moving to the next section:

   $ echo "Cluster: ${CLUSTER}, Region: ${REGION}, AWS Account ID: ${AWS_ACCOUNT_ID}"

   Note

   The "Cluster" output from the previous command may be the name of your cluster, the internal ID of your cluster, or the cluster’s domain prefix. If you prefer to use another identifier, you can manually set this value by running the following command:

   $ export CLUSTER=my-custom-value

Procedure

1. Create a new TLS secret from a private key and a public certificate, where fullchain.pem is your full wildcard certificate chain (including any intermediaries) and privkey.pem is your wildcard certificate’s private key:

   $ oc -n openshift-ingress create secret tls external-dns-tls --cert=fullchain.pem --key=privkey.pem

2. Create a new IngressController resource:

   $ cat << EOF | oc apply -f -
   apiVersion: operator.openshift.io/v1
   kind: IngressController
   metadata:
     name: external-dns-ingress
     namespace: openshift-ingress-operator
   spec:
     domain: ${DOMAIN}
     defaultCertificate:
       name: external-dns-tls
     endpointPublishingStrategy:
       loadBalancer:
         dnsManagementPolicy: Unmanaged
         providerParameters:
           aws:
             type: NLB
           type: AWS
         scope: External
       type: LoadBalancerService
   EOF

   Warning

   This IngressController example will create an internet accessible Network Load Balancer (NLB) in your AWS account. To provision an internal NLB instead, set the .spec.endpointPublishingStrategy.loadBalancer.scope parameter to Internal before creating the IngressController resource.

3. Verify that your custom domain IngressController has successfully created an external load balancer:

   $ oc -n openshift-ingress get service/router-external-dns-ingress

   Example output

   NAME                          TYPE           CLUSTER-IP      EXTERNAL-IP                                                                     PORT(S)                      AGE
   router-external-dns-ingress   LoadBalancer   172.30.71.250   a4838bb991c6748439134ab89f132a43-aeae124077b50c01.elb.us-east-1.amazonaws.com   80:32227/TCP,443:30310/TCP   43s

1. Retrieve the Amazon Route 53 public hosted zone ID:

   $ export ZONE_ID=$(aws route53 list-hosted-zones-by-name --output json \
     --dns-name "${DOMAIN}." --query 'HostedZones[0]'.Id --out text | sed 's/\/hostedzone\///')

2. Prepare a document with the necessary DNS changes to enable DNS resolution for the canonical domain of the Ingress Controller:

   $ NLB_HOST=$(oc -n openshift-ingress get service/router-external-dns-ingress -ojsonpath="{.status.loadBalancer.ingress[0].hostname}")
   $ cat << EOF > "${SCRATCH}/create-cname.json"
   {
     "Comment":"Add CNAME to ingress controller canonical domain",
     "Changes":[{
         "Action":"CREATE",
         "ResourceRecordSet":{
           "Name": "router-external-dns-ingress.${DOMAIN}",
         "Type":"CNAME",
         "TTL":30,
         "ResourceRecords":[{
           "Value": "${NLB_HOST}"
         }]
       }
     }]
   }
   EOF

   The External DNS Operator uses this canonical domain as the target for CNAME records.

3. Submit your changes to Amazon Route 53 for propagation:

   aws route53 change-resource-record-sets \
     --hosted-zone-id ${ZONE_ID} \
     --change-batch file://${SCRATCH}/create-cname.json

4. Create an AWS IAM Policy document that allows the External DNS Operator to update only the custom domain public hosted zone:

   $ cat << EOF > "${SCRATCH}/external-dns-policy.json"
   {
     "Version": "2012-10-17",
     "Statement": [
       {
         "Effect": "Allow",
         "Action": [
           "route53:ChangeResourceRecordSets"
         ],
         "Resource": [
           "arn:aws:route53:::hostedzone/${ZONE_ID}"
         ]
       },
       {
         "Effect": "Allow",
         "Action": [
           "route53:ListHostedZones",
           "route53:ListResourceRecordSets"
         ],
         "Resource": [
           "*"
         ]
       }
     ]
   }
   EOF

5. Create an AWS IAM user:

   $ aws iam create-user --user-name "${CLUSTER}-external-dns-operator"

6. Attach the policy:

   $ aws iam attach-user-policy --user-name "${CLUSTER}-external-dns-operator" --policy-arn $POLICY_ARN

   Note

   This will be changed to STS using IRSA in the future.

7. Create AWS keys for the IAM user:

   $ SECRET_ACCESS_KEY=$(aws iam create-access-key --user-name "${CLUSTER}-external-dns-operator")

8. Create static credentials:

   $ cat << EOF > "${SCRATCH}/credentials"
   [default]
   aws_access_key_id = $(echo $SECRET_ACCESS_KEY | jq -r '.AccessKey.AccessKeyId')
   aws_secret_access_key = $(echo $SECRET_ACCESS_KEY | jq -r '.AccessKey.SecretAccessKey')
   EOF

1. Create a new project:

   $ oc new-project external-dns-operator

2. Install the External DNS Operator from OperatorHub:

   $ cat << EOF | oc apply -f -
   apiVersion: operators.coreos.com/v1
   kind: OperatorGroup
   metadata:
     name: external-dns-group
     namespace: external-dns-operator
   spec:
     targetNamespaces:
     - external-dns-operator
   ---
   apiVersion: operators.coreos.com/v1alpha1
   kind: Subscription
   metadata:
     name: external-dns-operator
     namespace: external-dns-operator
   spec:
     channel: stable-v1.1
     installPlanApproval: Automatic
     name: external-dns-operator
     source: redhat-operators
     sourceNamespace: openshift-marketplace
   EOF

3. Wait until the External DNS Operator is running:

   $ oc rollout status deploy external-dns-operator --timeout=300s

4. Create a secret from the AWS IAM user credentials:

   $ oc -n external-dns-operator create secret generic external-dns \
     --from-file "${SCRATCH}/credentials"

5. Deploy the ExternalDNS controller:

   $ cat << EOF | oc apply -f -
   apiVersion: externaldns.olm.openshift.io/v1beta1
   kind: ExternalDNS
   metadata:
     name: ${DOMAIN}
   spec:
     domains:
       - filterType: Include
         matchType: Exact
         name: ${DOMAIN}
     provider:
       aws:
         credentials:
           name: external-dns
       type: AWS
     source:
       openshiftRouteOptions:
         routerName: external-dns-ingress
       type: OpenShiftRoute
     zones:
       - ${ZONE_ID}
   EOF

6. Wait until the controller is running:

   $ oc rollout status deploy external-dns-${DOMAIN} --timeout=300s

1. Create a new project for your sample application:

   $ oc new-project hello-world

2. Deploy a hello world application:

   $ oc new-app -n hello-world --image=docker.io/openshift/hello-openshift

3. Create a route for the application specifying your custom domain name:

   $ oc -n hello-world create route edge --service=hello-openshift hello-openshift-tls \
   --hostname hello-openshift.${DOMAIN}

4. Check if the DNS record was created automatically by ExternalDNS:

   Note

   It can take a few minutes for the record to appear in Amazon Route 53.

   $ aws route53 list-resource-record-sets --hosted-zone-id ${ZONE_ID} \
      --query "ResourceRecordSets[?Type == 'CNAME']" | grep hello-openshift

5. Optional: You can also view the TXT records that indicate they were created by ExternalDNS:

   $ aws route53 list-resource-record-sets --hosted-zone-id ${ZONE_ID} \
      --query "ResourceRecordSets[?Type == 'TXT']" | grep ${DOMAIN}

6. Curl the newly created DNS record to your sample application to verify the hello world application is accessible:

   $ curl https://hello-openshift.${DOMAIN}

   Example output

   Hello OpenShift!