You can easily set up intelligent multicluster routing for active-active and active-passive workloads in your environment by using virtual destinations. With virtual destinations, you can define unique internal hostnames for apps that are spread across multiple clusters, and route to these apps via these hostnames.

Figure: Multicluster routing with Gloo Mesh Gateway

For more information, see the following resources:

Before you begin

  1. Set up Gloo Mesh Gateway in a single cluster.
  2. Follow the other guides in this routing section to plan your routing table setup. For example, you might check out the path matching guide to decide how to match the incoming requests to your service paths, the redirect guide to set up any path or host rewrites, or the sub-table delegation guide to nest and sort multiple route tables. Note: Be sure that each route for one host is unique, such as by using prefix matching to determine which requests to the host should be forwarded to which destinations.

Set up multicluster routing for north-south traffic

To route incoming requests from your ingress gateway to an app that is spread across clusters based on locality, you create a virtual destination for your multicluster app, and a route table that forwards traffic to that virtual destination.

  1. If you have not already, create a virtual gateway in the cluster where you deployed an instance of your global app. This virtual gateway selects the default Istio ingress gateway, which routes incoming traffic (north-south) to your service mesh. For more information about setting up virtual gateways, see the gateway listener guides.

      kubectl apply -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: VirtualGateway
metadata:
  name: istio-ingressgateway
  namespace: gloo-mesh
spec:
  workloads:
    # Matches on 'spec.selector' labels for the ingress gateway service
    - selector:
        labels:
          istio: ingressgateway
  listeners:
    # The port the ingress gateway listens on for incoming requests to route
    - port:
        number: 80
      http: {}
EOF

  2. In each cluster where you deployed an instance of your global app, ensure that the app is exposed by a Kubernetes service. Make sure that you use the same label for your services as this label serves as the selector to later identify all the services across your clusters that make up your global app. In this example, the label app: global-app is used. The service listens on port 3456 and forwards requests to port 9080.

      apiVersion: v1
kind: Service
metadata:
  labels:
    app: global-app
  name: global-app
  namespace: global
spec:
  ports:
  - name: http
    port: 3456
    protocol: TCP
    targetPort: 9080
  type: ClusterIP

  3. Create a virtual destination resource and define a unique hostname that the virtual gateway can use to send requests to. This virtual destination is configured to listen for incoming traffic on the internal-only, arbitrary hostname app.internal.com:8080. Incoming requests can then be routed to any service instances with the label app: global-app on port 9080. Note that because virtual destinations are dynamic, the ingress gateway load balances the request across healthy app instance.

      kubectl apply -n global -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: VirtualDestination
metadata:
  name: global-app-vd
  namespace: global
spec:
  hosts:
  # Arbitrary, internal-only hostname assigned to the endpoint
  - app.internal.com
  ports:
  - number: 8080
    protocol: HTTP
    targetPort:
      number: 9080
  services:
    - labels:
        app: global-app
EOF

  4. Create a route table to route requests to your services. A route table allows you to define how requests to endpoints should be routed. In this example route table, all requests to the /global-app path are routed to the global-app virtual destination.

      kubectl apply -n global -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: global-app-routes
  namespace: global
spec:
  # Applies to any host; can indicate a specific domain, like example.com
  hosts:
    - '*'
  # Selects the virtual gateway you previously created
  virtualGateways:
    - name: istio-ingressgateway
      namespace: bookinfo
      cluster: ${CLUSTER_NAME}
  http:
    # Route for the global-app service
    - name: global-app
      # Prefix matching
      matchers:
      - uri:
          prefix: /global-app
      # Forwarding directive
      forwardTo:
        destinations:
          # Reference to the virtual destination for the global-app svcs
          - ref:
              name: global-app-vd
            kind: VIRTUAL_DESTINATION
            port:
              number: 8080
EOF

  5. Get the external address of your ingress gateway.

      export INGRESS_GW_IP=$(kubectl get svc -n gloo-mesh-gateways istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
echo $INGRESS_GW_IP
  
      export INGRESS_GW_IP=$(kubectl get svc -n gloo-mesh-gateways istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].hostname}')
echo $INGRESS_GW_IP

  6. Test the route to your app by curling the ingress gateway address and app path. For example, the following command appends /global-app for the sample app.

      curl http://$INGRESS_GW_IP/global-app

Next steps

Now that you have basic routes set up, you can explore more advanced networking scenarios.

  • Other routing actions: For HTTP routes, you can set up other actions besides forwarding requests. For example, you might check out the prefix matching guide to decide how to match the incoming requests to your service paths, the redirect guide to set up any path or prefix rewrites, or the sub-table delegation guide to nest and sort multiple route tables.
  • Additional route settings: Configure additional route settings, such as weighted routing to version subsets or adding and removing headers.
  • Policies: For more control over traffic behavior, apply traffic management, security, or resiliency policies to your service or route, such as for outlier detection, failover, fault injection, or keep alive connections.