# Multiple Gateways/Service Networks and HTTPRoute Associates to Multiple Gateways

## Multiple Gateways/Service Networks Usecase

Here is one popular multi-cluster architecture:

* config cluster, where is used for configuration management
* multiple work-load cluster(s), where are used to run application workload(s)

You can see a production usecase at AirBnb [airbnb mullti-cluster](https://www.youtube.com/watch?v=1D8lg36ZNHs)

Here is our example

![Config Cluster and multiple workload cluster](images/multi-sn.png)

* there are 2 gateway(s), gateway-1/lattice-service-network-1 and gateway-2/lattice-service-network-2
* gateway-1 contains HTTPRoute1 and HTTPRoute2
* gateway-2 contains HTTPRoute2 and HTTPRoute3
* blue workload cluster(s) are using gateway-1 to access HTTPRoute1 an HTTPRoute2
* orange workload cluster(s) are using gateway-2 to access HTTPRoute2 an HTTPRoute3

###  Config Cluster Gateway Configuration

```
# gateway-1
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: gateway-1
  annotations:
    application-networking.k8s.aws/lattice-vpc-association: "false"  # not associate to VPC
spec:
  gatewayClassName: amazon-vpc-lattice
  listeners:
  ...
```  

```
# gateway-2
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: gateway-2
  annotations:
    application-networking.k8s.aws/lattice-vpc-association: "false"  # not associate to VPC
spec:
  gatewayClassName: amazon-vpc-lattice
  listeners:
  ...
```  

```
# httproute-1
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: httproute-1
spec:
  parentRefs:
  - name: gateway-1  # part of gateway-1/service-network-1
  ...
```  

```
# httproute-2
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: httproute-2
spec:
  parentRefs:
  - name: gateway-1     # part of both gateway-1 and gateway-2 
    sectionName: http
  - name: gateway-2
    sectionName: http
  ...    
  ```

  ```
# httproute-3
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: httproute-3
spec:
  parentRefs:
  - name: gateway-2  # part of gateway-2/service-network-2
  ...
```

### blue workload cluster(s)
Associate cluster's VPC to gateway-1/service-network-1 so that all Pod(s) in blue workload clusters can access HTTPRoute(s)of gateway-1, HTTPRoute-1 and HTTPRoute-2

```
# gateway-1
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: gateway-1
  annotations:
    application-networking.k8s.aws/lattice-vpc-association: "true"  #  associate to VPC
spec:
  gatewayClassName: amazon-vpc-lattice
  listeners:
  ...
```  

### orange workload cluster(s)
Associate cluster's VPC to gateway-2/service-network-2, so that all Pod(s) in orange workload clusters can access HTTPRoute(s) of gateway-2, HTTPRoute-2 an HTTPRoute-3

```
# gateway-2
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: gateway-2
  annotations:
    application-networking.k8s.aws/lattice-vpc-association: "true"  #  associate to VPC
spec:
  gatewayClassName: amazon-vpc-lattice
  listeners:
  ...
```  

## Defining HTTPRoute in Config Cluster

![ServiceImport](images/serviceimport.png)

### Exporting Kubernetes Service to AWS Lattice Service

In workload cluster, exports k8s service to AWS VPC lattice

```
# in workload cluster(s)
apiVersion: multicluster.x-k8s.io/v1alpha1
kind: ServiceExport
metadata:
  name: service-1
  annotations:
          multicluster.x-k8s.io/federation: "amazon-vpc-lattice"  #  AWS VPC Lattice
``` 

### Configure HTTPRoute in config cluster to reference K8S service(s) in worload cluster(s)

```
# in config cluster
apiVersion: multicluster.x-k8s.io/v1alpha1
kind: ServiceImport
metadata:
  name: service-1
spec:
  type: ClusterSetIP
  ports:
  - port: 80
    protocol: TCP
```

```
# httproute 
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: httproute-1
spec:
  parentRefs:
  - name: gateway-1
    sectionName: http 
  rules:
  - backendRefs:  
    - name: service-1
      kind: ServiceImport
      weight: 25
    - name: service-2
      kind: ServiceImport
      weight: 25  
    - name: service-3
      kind: ServiceImport
      weight: 25
    - name: service-4
      kind: ServiceImport
      weight: 25    
```