This procedure describes adding additional Anthos Service Mesh (ASM) gateways to your Apigee hybrid installation.
Installing additional Anthos Service Mesh gateways
  In the ASM overlay.yaml file you can add more ingress gateways by
  following a similar pattern as the one below. Note that the 
  spec.components[].label and spec.components[].k8s.service.selector
  elements allow you to associate a named ingress gateway with a specific virtual host, as
  explained in Targeting an ingress to a virtual host.
  apiVersion: install.istio.io/v1alpha1
  kind: IstioOperator
  spec:
    profile: asm-gcp
    # hub: gcr.io/gke-release/asm # {"$ref":"#/definitions/io.k8s.cli.setters.anthos.servicemesh.hub"}
    components:
      ingressGateways:
      - name: istio-ingressgateway-dairy
        enabled: true
        label:
          app: istio-ingressgateway
          ingress_name: dairy
        k8s:
          service:
            selector:
              app: istio-ingressgateway
              ingress_name: dairy
            type: LoadBalancer
            ports:
            - name: status-port
              port: 15021
            - name: http2
              port: 80
              targetPort: 8080
            - name: https
              port: 443
              targetPort: 8443
          hpaSpec:
            minReplicas: 1
            maxReplicas: 10
      - name: istio-ingressgateway-vegetables
        enabled: true
        label:
          app: istio-ingressgateway
          ingress_name: vegetables
        k8s:
          service:
            selector:
              app: istio-ingressgateway
              ingress_name: vegetables
            ports:
            - name: http2
              port: 80
              targetPort: 8080
            - name: status-port
              port: 15020
            - name: https
              port: 443
              targetPort: 8443
          hpaSpec:
            minReplicas: 1
            maxReplicas: 10
          resources:
            requests:
              cpu: 300m
              memory: 128Mi
  Follow the Anthos Service Mesh documentation for your platform to apply the changes.
Targeting an ASM/istio ingress to a virtual host
You can target a labeled ASM/istio ingress gateway to a specific virtual host in your overrides file.
    This configuration specifies the ingress gateway where Apigee will apply the virtual host's configuration. In
    the following example, traffic to virtual host milk-vh is directed through
    the ingress labeled dairy and traffic to the other two virtual hosts goes through
    the vegetables ingress. The ingresses must be properly labeled, as explained in
    Installing additional Apigee ingress gateway gateways.
  
  
  
virtualhosts:
  - name: milk-vh
    sslCertPath: cert-milk.crt
    sslKeyPath: cert-milk.key
    selector:
      app: istio-ingressgateway
      ingress_name: dairy
  
  - name: carrots-vh
    sslCertPath: cert-carrots.crt
    sslKeyPath: cert-carrots.key
    selector:
      app: istio-ingressgateway
      ingress_name: vegetables
  
  - name: ginger-vh
    sslCertPath: cert-ginger.crt
    sslKeyPath: cert-ginger.key
    selector:
      app: apigee-ingressgateway
      ingress_name: vegetables