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Route to services external to the mesh

After you configure your route table, you can use it to forward requests to services or resources that are external to the service mesh.

In some cases, one of your Istio-managed apps might need to communicate with services that are external to the service mesh. For example, your app might need to contact a public API or an on-prem database. To route requests to services that are external to your service mesh, you assign a unique internal hostname to your external endpoint that your in-mesh services use to send requests to.

In this guide, you create Gloo Mesh ExternalEndpoint and ExternalService resources. Gloo Mesh translates these resources into an Istio ServiceEntry.

Because external endpoints cannot be automatically discovered by Gloo Mesh, you create a Gloo Mesh ExternalEndpoint resource to specify the hostname or IP address, the port, and the protocol of the external endpoint that you want to reach.
Then, you create a Gloo Mesh ExternalService resource to expose all of the external endpoints under a unique internal hostname.

Routing to external services based on locality

For more information, see the following resources:

Routing to external services concept doc
Gloo Mesh API docs for ExternalEndpoint
Gloo Mesh API docs for ExternalService

Before you begin

Install Gloo Mesh, register workload clusters, and install Istio into each workload cluster. For example, you might follow the demo setup to get a testing environment up and running, or the docs in the installation guide to set up your production-level environment. To enable multicluster routing, ensure that you deploy an east-west gateway.
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.

Route to external services

Create a virtual gateway that selects the default Istio ingress gateway, which routes incoming traffic (north-south) to your service mesh.

kubectl apply --context $REMOTE_CONTEXT1 -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: VirtualGateway
metadata:
  name: ingress-gateway
  namespace: gloo-mesh
spec:
  workloads:
    # Selects the istio ingress gateway in workload cluster 1
    - selector:
        labels:
          istio: ingressgateway
        cluster: ${REMOTE_CLUSTER1}
  listeners:
    # The port the ingress gateway listens on for incoming requests to route
    - port:
        number: 80
      http: {}
EOF

Save the public address of the Istio ingress gateway.

GKE: LoadBalancer IP address
EKS: LoadBalancer hostname


   export CLUSTER_1_INGRESS_ADDRESS=$(kubectl --context $REMOTE_CONTEXT1 get svc -n istio-system istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
   echo $CLUSTER_1_INGRESS_ADDRESS


   export CLUSTER_1_INGRESS_ADDRESS=$(kubectl --context $REMOTE_CONTEXT1 get svc -n istio-system istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].hostname}')
   echo $CLUSTER_1_INGRESS_ADDRESS

Get the address and ports that your external resource listens on. For example, the address might be a static IP address or a registered URL.

Create an external endpoint for each address and an external service. The external endpoint represents the server or service outside of your service mesh that you want to reach. By using a Gloo Mesh external service, you can then assign a unique hostname to this external endpoint that services in your mesh can use to send requests. You can also use this service to route incoming requests from your ingress gateway directly to your external endpoint.

Static IP address
Registered hostname

Use the address and ports to create an external endpoint resource. In these examples, two external endpoints are created for two static IP addresses that an on-prem database is exposed by.

kubectl apply --context $REMOTE_CONTEXT1 -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: ExternalEndpoint
metadata:
  name: db1-external-endpoint
  namespace: global
  labels:
    # Label that the external service will select
    external-endpoint: db
spec:
  # Static IP address for on-prem service
  address: 123.45.67.8
  ports:
    - name: myport
      number: 9080
EOF
 
kubectl apply --context $REMOTE_CONTEXT1 -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: ExternalEndpoint
metadata:
  name: db2-external-endpoint
  namespace: global
  labels:
    # Label that the external service will select
    external-endpoint: db
spec:
  # Static IP address for on-prem service
  address: 123.45.67.9
  ports:
    - name: myport
      number: 9080
EOF

Create an external service resource to expose the external endpoint inside your mesh. In this example, you select all endpoints with the external-endpoint: db label. Note that the hosts field is not required to match the address that you specified in the external endpoint, because this host is an internal address that is used only by the gateways and services within your service mesh.

kubectl apply --context $REMOTE_CONTEXT1 -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: ExternalService
metadata:
  name: db-external-service
  namespace: global
spec:
  hosts:
  # Arbitrary, internal-only hostname assigned to the endpoint
  - "my-remote-db.com"
  ports:
  - name: http
    number: 80
    protocol: HTTP
    targetPort: 9080
  selector:
    # Selects the endpoint label
    external-endpoint: db
 EOF

Use the address and ports to create an external endpoint resource. In this example, the external endpoint can be reached by using the httpbin.org address, and the ports 80 and 443.

kubectl apply --context $REMOTE_CONTEXT1 -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: ExternalEndpoint
metadata:
  name: httpbin-external-endpoint
  namespace: global
  labels:
    # Label that the external service will select
    external-endpoint: httpbin
spec:
  # Registered URL for external service
  address: httpbin.org
  ports:
    - name: http
      number: 80
    - name: https
      number: 443
EOF

Create an external service resource to expose the external endpoint inside your mesh. In this example, you select all external endpoints with the external-endpoint: httpbin label. Note that the hosts field is not required to match the address that you specified in the external endpoint, because this host is an internal address that is used only by the gateways and services within your service mesh.

kubectl apply --context $REMOTE_CONTEXT1 -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: ExternalService
metadata:
  name: httpbin-external-service
  namespace: global
spec:
  hosts:
  # Arbitrary, internal-only hostname assigned to the endpoint
  - "my-remote-svc.com"
  ports:
  - name: http
    number: 80
    protocol: HTTP
  selector:
    # Selects the endpoint label
    external-endpoint: httpbin
 EOF

Create a route table to route requests to the external service. A route table allows you to define how requests to endpoints should be routed, and is translated to the Istio VirtualService resource. In this example route table, all requests to the /httpbin path are routed to the endpoints that back the httpbin-external-service.

Static IP address
Registered hostname


   kubectl apply --context $REMOTE_CONTEXT1 -n global -f- <<EOF
   apiVersion: networking.gloo.solo.io/v2
   kind: RouteTable
   metadata:
     name: db-routes
     namespace: global
   spec:
     # Applies to any host; can indicate a specific host
     hosts:
       - '*'
     # Selects the virtual gateway you previously created
     virtualGateways:
       - name: ingress-gateway
         namespace: gloo-mesh
         cluster: ${REMOTE_CLUSTER1}
     http:
       # Route for the db-external-service
       - name: db-app
         # Prefix matching
         matchers:
         - uri:
             prefix: /db
         # Forwarding directive
         forwardTo:
           destinations:
             # Reference to the external service exposing your external endpoints
             - ref:
                 name: db-external-service
               kind: EXTERNAL_SERVICE
   EOF


   kubectl apply --context $REMOTE_CONTEXT1 -n global -f- <<EOF
   apiVersion: networking.gloo.solo.io/v2
   kind: RouteTable
   metadata:
     name: httpbin-routes
     namespace: global
   spec:
     hosts:
       - '*'
     # Selects the virtual gateway you previously created
     virtualGateways:
       - name: ingress-gateway
         namespace: gloo-mesh
         cluster: ${REMOTE_CLUSTER1}
     http:
       # Route for the httpbin-external-service
       - name: httpbin-app
         # Prefix matching
         matchers:
         - uri:
             prefix: /httpbin
         # Forwarding directive
         forwardTo:
           destinations:
             # Reference to the external service exposing your external endpoints
             - ref:
                 name: httpbin-external-service
               kind: EXTERNAL_SERVICE
   EOF

Test the route to your external resource by curling the ingress gateway address and path. For example, the following command appends /httpbin for the external httpbin app.
```
curl http://$CLUSTER_1_INGRESS_ADDRESS/httpbin
```

Next steps

If you haven't already, follow the other guides in the routing section to plan your routing table setup. 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.
Configure additional route settings, such as weighted routing to version subsets or adding and removing headers.