Use a multi-cluster Ingress

Step 1: Map the multi-cluster Service to clusters with Ingresses

For each cluster that will host an Ingress, follow the steps in Use the CLI to configure MCS:

1. In each cluster, create a ServiceExport to export the local Service to the multi-cluster Service.

2. In each cluster that hosts an Ingress, create a ServiceImport to import the multi-cluster Service. The imported Service is automatically named amcs-{Service name} (for example, amcs-nginx).

3. Verify the imported Service in each Ingress-hosting cluster:

   kubectl get service amcs-nginx

   Expected output:

   NAME         TYPE        CLUSTER-IP        EXTERNAL-IP   PORT(S)   AGE
   amcs-nginx   ClusterIP   192.168.118.171   <none>        80/TCP    34m

   kubectl get endpointslice

   Expected output:

   NAME                                                     ADDRESSTYPE   PORTS   ENDPOINTS               AGE
   imported-c0c4a2c9339e44235a5228d0b0ff2259c-nginx-vnlnd   IPv4          80      10.0.2.4,10.0.2.5       34m
   imported-ce962c460ae284243a3161d6f2c7b4cf7-nginx-d8rr5   IPv4          80      10.0.2.221,10.0.2.236   29m
   imported-ca5b667538054499ab399588efe4ab654-nginx-xfe1a   IPv4          80      10.0.2.145,10.0.2.123   20m

   Each row in the ENDPOINTS column corresponds to the pod IPs in one of the associated clusters. If your setup has three clusters, you should see three EndpointSlice entries. Cross-reference each IP range with pod IPs in each cluster to confirm the import is correct.

Step 2: Configure Ingress rules

Run the following steps in each cluster that hosts an Ingress.

1. Create a file named ingress.yaml with the following content:

   apiVersion: networking.k8s.io/v1
   kind: Ingress
   metadata:
     name: multi-cluster-nginx-ingress
   spec:
     rules:
     - host: example.com
       http:
         paths:
         - path: /
           pathType: Prefix
           backend:
             service:
               name: amcs-nginx
               port: 80

2. Apply the Ingress:

   kubectl apply -f ingress.yaml

3. Query the Ingress endpoints of the clusters that are configured with Ingresses to get the external IP address assigned to each Ingress:

   # ACK Cluster 1
   kubectl get ingress
   NAME                          CLASS   HOSTS         ADDRESS         PORTS   AGE
   multi-cluster-nginx-ingress   nginx   example.com   XX.XX.XX.XX     80      26m
   
   # ACK Cluster 2
   kubectl get ingress
   NAME                          CLASS   HOSTS         ADDRESS         PORTS   AGE
   multi-cluster-nginx-ingress   nginx   example.com   XX.XX.XX.XX     80      26m

   Note the value in the ADDRESS column for each cluster. You will use these IP addresses in the next step when you create DNS records.

Step 3: Set up DNS resolution

Create an A record for each Ingress-hosting cluster that maps your domain name to the Ingress IP address you retrieved in Step 2. For instructions, see Add DNS records.

For example, if ACK Cluster 1 has Ingress IP 1.2.3.4 and ACK Cluster 2 has Ingress IP 5.6.7.8, create two A records for example.com: one pointing to 1.2.3.4 and one pointing to 5.6.7.8. DNS will distribute traffic between the two clusters.