Container Service for Kubernetes:Access Services across clusters by using domain names

Architecture

Prerequisites

Before you begin, ensure that you have:

• Fleet management enabled. See Enable multi-cluster management

• Two clusters associated with a Fleet instance: one acting as the provider cluster and one as the consumer cluster. See Manage associated clusters

• Kubernetes version 1.22 or later on both clusters

• Pod-level network connectivity between the two clusters. See MCS overview

  Note

  After enabling pod CIDR connectivity, update the security group rules for each cluster's node pools to allow traffic from the pod CIDR blocks of the interconnected clusters.

• The kubeconfig files for the provider cluster, consumer cluster, and Fleet instance, with kubectl configured to connect to each. See Obtain the kubeconfig file of a cluster and use kubectl to connect to the cluster

Step 1: Deploy a Service in the provider cluster

Connect to the provider cluster using its kubeconfig file. Create a file named web-demo-svc-provider.yaml with the following content:

apiVersion: v1
kind: Service
metadata:
  name: service1
  namespace: provider-ns
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 8080
  selector:
    app: web-demo
  sessionAffinity: None
  type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-demo
  namespace: provider-ns
spec:
  replicas: 1
  selector:
    matchLabels:
      app: web-demo
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: web-demo
    spec:
      containers:
      - env:
        - name: ENV_NAME
          value: cluster-provider
        image: registry-cn-hangzhou.ack.aliyuncs.com/acs/web-demo:0.5.0
        imagePullPolicy: Always
        name: web-demo
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler

Apply the manifest:

kubectl apply -f web-demo-svc-provider.yaml

Verify that the Service and Pod are running:

kubectl get svc,pod -n provider-ns

Expected output:

NAME               TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
service/service1   ClusterIP   <cluster-ip>   <none>        80/TCP    1m

NAME                           READY   STATUS    RESTARTS   AGE
pod/web-demo-<suffix>          1/1     Running   0          1m

Step 2: Create a Service in the consumer cluster

Connect to the consumer cluster using its kubeconfig file. Create a file named web-demo-svc-consumer.yaml with the following content:

apiVersion: v1
kind: Service
metadata:
  name: service1
  namespace: provider-ns
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 8080
  selector:
    app: web-demo
  sessionAffinity: None
  type: ClusterIP

Apply the manifest:

kubectl apply -f web-demo-svc-consumer.yaml

Verify that the Service exists:

kubectl get svc service1 -n provider-ns

Expected output:

NAME       TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
service1   ClusterIP   <cluster-ip>   <none>        80/TCP    30s

Step 3: Create a MultiClusterService on the Fleet instance

Connect to the Fleet instance using its kubeconfig file. Create a file named multiclusterservice.yaml with the following content:

apiVersion: networking.one.alibabacloud.com/v1alpha1
kind: MultiClusterService
metadata:
   name: service1
   namespace: provider-ns
spec:
  consumerClusters:
    - name: <your consumer cluster id>
  providerClusters:
    - name: <your provider cluster id>

Apply the manifest:

kubectl apply -f multiclusterservice.yaml

Verify that the MultiClusterService was created and synced successfully:

kubectl describe multiclusterservice service1 -n provider-ns

In the output, check the Status section for conditions showing that the configuration has been propagated to both clusters. Proceed to the next step only after the sync is confirmed.

Step 4: Verify cross-cluster access from the consumer cluster

Connect to the consumer cluster using its kubeconfig file. Create a file named client-pod.yaml with the following content:

apiVersion: v1
kind: Pod
metadata:
  name: curl-client
  namespace: customer-ns
spec:
  containers:
  - name: curl-client
    image: registry-cn-hangzhou.ack.aliyuncs.com/dev/curl:8.11.1
    command: ["sh", "-c", "sleep 12000"]

Deploy the client pod:

kubectl apply -f client-pod.yaml

Wait for the pod to reach Running state, then open a shell in it and send a request to service1 in the provider cluster:

kubectl exec -it -ncustomer-ns curl-client -- sh

curl service1.provider-ns

Expected output:

This is cluster-provider!

The response confirms that traffic is being routed to the backend pods in the provider cluster.

What's next

• MCS overview — Learn more about how the MCS feature works and the networking requirements between clusters.

• GitOps — Manage and distribute Kubernetes resources across Fleet member clusters using a GitOps workflow.

• Application distribution — Use the Fleet instance to distribute applications to associated clusters at scale.