Chapter 1. About gateways

Procedure

1. Create a namespace that you will use to install the gateway.

   $ oc create namespace <gateway_namespace>

   Note

   Install the gateway and the Istio control plane in different namespaces.

   You can install the gateway in a dedicated gateway namespace. This approach allows the gateway to be shared by many applications operating in different namespaces. Alternatively, you can install the gateway in an application namespace. In this approach, the gateway acts as a dedicated gateway for the application in that namespace.

2. Create a YAML file named secret-reader.yml that defines the service account, role, and role binding for the gateway deployment. These settings enable the gateway to read the secrets, which is required for obtaining TLS credentials.

   apiVersion: v1
   kind: ServiceAccount
   metadata:
     name: secret-reader
     namespace: <gateway_namespace>
   ---
   apiVersion: rbac.authorization.k8s.io/v1
   kind: Role
   metadata:
     name: secret-reader
     namespace: <gateway_namespace>
   rules:
     - apiGroups: [""]
       resources: ["secrets"]
       verbs: ["get", "watch", "list"]
   ---
   apiVersion: rbac.authorization.k8s.io/v1
   kind: RoleBinding
   metadata:
     name:  secret-reader
     namespace: <gateway_namespace>
   roleRef:
     apiGroup: rbac.authorization.k8s.io
     kind: Role
     name: secret-reader
   subjects:
     - kind: ServiceAccount
       name:  secret-reader

3. Apply the YAML file by running the following command:

   $ oc apply -f secret-reader.yml

4. Create a YAML file named gateway-deployment.yml that defines the Kubernetes Deployment object for the gateway.

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: <gateway_name>
     namespace: <gateway_namespace>
   spec:
     selector:
       matchLabels:
         istio: <gateway_name>
     template:
       metadata:
         annotations:
           inject.istio.io/templates: gateway 1
         labels:
           istio: <gateway_name> 2
           sidecar.istio.io/inject: "true" 3
       spec:
         containers:
           - name: istio-proxy
             image: auto 4
             securityContext:
               capabilities:
                 drop:
                 - ALL
               allowPrivilegeEscalation: false
               privileged: false
               readOnlyRootFilesystem: true
               runAsNonRoot: true
             ports:
             - containerPort: 15090
               protocol: TCP
               name: http-envoy-prom
             resources:
               limits:
                 cpu: 2000m
                 memory: 1024Mi
               requests:
                 cpu: 100m
                 memory: 128Mi
         securityContext:
           sysctls:
           - name: net.ipv4.ip_unprivileged_port_start
             value: "0"
         serviceAccountName: secret-reader 5

   1

   Indicates that the Istio control plane uses the gateway injection template instead of the default sidecar template.

   2

   Ensure that a unique label is set for the gateway deployment. A unique label is required so that Istio Gateway resources can select gateway workloads.

   3

   Enables gateway injection by setting the sidecar.istio.io/inject label to true. If the name of the Istio resource is not default you must use the istio.io/rev: <istio_revision> label instead, where the revision represents the active revision of the Istio resource.

   4

   Sets the image field to auto so that the image automatically updates each time the pod starts.

   5

   Sets the serviceAccountName to the name of the ServiceAccount created previously.

5. Apply the YAML file by running the following command:

   $ oc apply -f gateway-deployment.yml

6. Verify that the gateway Deployment rollout was successful by running the following command:

   $ oc rollout status deployment/<gateway_name> -n <gateway_namespace>

   You should see output similar to the following:

   Example output

   Waiting for deployment "<gateway_name>" rollout to finish: 0 of 1 updated replicas are available...
   deployment "<gateway_name>" successfully rolled out

7. Create a YAML file named gateway-service.yml that contains the Kubernetes Service object for the gateway.

   apiVersion: v1
   kind: Service
   metadata:
     name: <gateway_name>
     namespace: <gateway_namespace>
   spec:
     type: ClusterIP 1
     selector:
       istio: <gateway_name> 2
     ports:
       - name: status-port
         port: 15021
         protocol: TCP
         targetPort: 15021
       - name: http2
         port: 80
         protocol: TCP
         targetPort: 80
       - name: https
         port: 443
         protocol: TCP
         targetPort: 443

   1

   When you set spec.type to ClusterIP the gateway Service object can be accessed only from within the cluster. If the gateway has to handle ingress traffic from outside the cluster, set spec.type to LoadBalancer. Alternatively, you can use OpenShift Routes.

   2

   Set the selector to the unique label or set of labels specified in the pod template of the gateway deployment that you previously created.

8. Apply the YAML file by running the following command:

   $ oc apply -f gateway-service.yml

9. Verify that the gateway service is targeting the endpoint of the gateway pods by running the following command:

   $ oc get endpoints <gateway_name> -n <gateway_namespace>

   You should see output similar to the following example:

   Example output

   NAME              ENDPOINTS                             AGE
   <gateway_name>    10.131.0.181:8080,10.131.0.181:8443   1m

10. Optional: Create a YAML file named gateway-hpa.yml that defines a horizontal pod autoscaler for the gateway. The following example sets the minimum replicas to 2 and the maximum replicas to 5 and scales the replicas up when average CPU utilization exceeds 80% of the CPU resource limit. This limit is specified in the pod template of the deployment for the gateway.

    apiVersion: autoscaling/v2
    kind: HorizontalPodAutoscaler
    metadata:
      name: <gateway_name>
      namespace: <gateway_namespace>
    spec:
      minReplicas: 2
      maxReplicas: 5
      metrics:
      - resource:
          name: cpu
          target:
            averageUtilization: 80
            type: Utilization
        type: Resource
      scaleTargetRef:
        apiVersion: apps/v1
        kind: Deployment
        name: <gateway_name> 1

    1

    Set spec.scaleTargetRef.name to the name of the gateway deployment previously created.

11. Optional: Apply the YAML file by running the following command:

    $ oc apply -f gateway-hpa.yml

12. Optional: Create a YAML file named gateway-pdb.yml that defines a pod disruption budget for the gateway. The following example allows gateway pods to be evicted only when at least 1 healthy gateway pod will remain on the cluster after the eviction.

    apiVersion: policy/v1
    kind: PodDisruptionBudget
    metadata:
      name: <gateway_name>
      namespace: <gateway_namespace>
    spec:
      minAvailable: 1
      selector:
        matchLabels:
          istio: <gateway_name> 1

    1

    Set the spec.selector.matchLabels to the unique label or set of labels specified in the pod template of the gateway deployment previously created.

13. Optional: Apply the YAML file by running the following command:

    $ oc apply -f gateway-pdb.yml