Distributed traffic cross clusters

[dungdm93]

I have 2 clusters c1 and c2 join into the same Lattice service network. review app is deployed in both clusters:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: review
  namespace: demo
  labels:
    app: review
spec:
  replicas: 2
  selector:
    matchLabels:
      app: review
  template:
    metadata:
      labels:
        app: review
    spec:
      containers:
      - name: aug24-review
        image: public.ecr.aws/x2j8p8w7/http-server:latest
        env:
        - name: PodName
          value: "review c1" # <= change to `c2` when deployed in cluster c2
---
apiVersion: v1
kind: Service
metadata:
  name: review
  namespace: demo
spec:
  selector:
    app: review
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8090
---
apiVersion: application-networking.k8s.aws/v1alpha1
kind: ServiceExport
metadata:
  name: review
  namespace: demo
  annotations:
    application-networking.k8s.aws/federation: "amazon-vpc-lattice"

Then ONLY in cluster c1, create ServiceImport and HTTPRoute

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: review
  namespace: demo
spec:
  parentRefs:
  - name: my-hotel
    sectionName: http
  rules:
  - backendRefs:
    - name: review
      kind: ServiceImport
---
apiVersion: application-networking.k8s.aws/v1alpha1
kind: ServiceImport
metadata:
  name: review
  namespace: demo
spec:
  type: ClusterSetIP
  ports:
  - port: 80
    protocol: TCP

What I expected is traffic is distributed to review service in BOTH clusters, but it only sent to one cluster

while true; do curl http://review-demo-0833fb844c53faa83.7d67968.vpc-lattice-svcs.ap-southeast-1.on.aws; done
Requsting to Pod(review-76978c5ddc-l6qnt): review c2
Requsting to Pod(review-76978c5ddc-2fvn2): review c2
Requsting to Pod(review-76978c5ddc-l6qnt): review c2
Requsting to Pod(review-76978c5ddc-l6qnt): review c2
Requsting to Pod(review-76978c5ddc-l6qnt): review c2
Requsting to Pod(review-76978c5ddc-2fvn2): review c2
Requsting to Pod(review-76978c5ddc-2fvn2): review c2
Requsting to Pod(review-76978c5ddc-2fvn2): review c2
Requsting to Pod(review-76978c5ddc-l6qnt): review c2
Requsting to Pod(review-76978c5ddc-2fvn2): review c2
Requsting to Pod(review-76978c5ddc-2fvn2): review c2
Requsting to Pod(review-76978c5ddc-l6qnt): review c2
Requsting to Pod(review-76978c5ddc-l6qnt): review c2
Requsting to Pod(review-76978c5ddc-2fvn2): review c2
Requsting to Pod(review-76978c5ddc-l6qnt): review c2
Requsting to Pod(review-76978c5ddc-l6qnt): review c2

Only a target group is associated with Lattice service:

aws vpc-lattice list-target-groups --output=json
{
    "items": [
        {
            "arn": "arn:aws:vpc-lattice:ap-southeast-1:<account_id>:targetgroup/tg-049d500097172a647",
            "createdAt": "2025-07-02T07:13:44.975000+00:00",
            "id": "tg-049d500097172a647",
            "ipAddressType": "IPV4",
            "lastUpdatedAt": "2025-07-02T07:13:44.975000+00:00",
            "name": "k8s-demo-review-iebniqqsdb",
            "port": 80,
            "protocol": "HTTP",
            "serviceArns": [
                "arn:aws:vpc-lattice:ap-southeast-1:<account_id>:service/svc-0833fb844c53faa83"
            ],
            "status": "ACTIVE",
            "type": "IP",
            "vpcIdentifier": "vpc-0e296da2065d30703"
        },
        {
            "arn": "arn:aws:vpc-lattice:ap-southeast-1:<account_id>:targetgroup/tg-089edac66225da09a",
            "createdAt": "2025-07-02T07:13:38.700000+00:00",
            "id": "tg-089edac66225da09a",
            "ipAddressType": "IPV4",
            "lastUpdatedAt": "2025-07-02T07:13:38.700000+00:00",
            "name": "k8s-demo-review-qyilpffebc",
            "port": 80,
            "protocol": "HTTP",
            "serviceArns": [],
            "status": "ACTIVE",
            "type": "IP",
            "vpcIdentifier": "vpc-01054789f4f5ba088"
        }
    ]
}