#Installing a gateway via gateway injection

This procedure explains how to install a gateway by using gateway injection.

#Prerequisites

• Alauda Service Mesh v2 Operator is installed.
• An Istio control plane is deployed.
• Confirm Linux kernel compatibility.

#Procedure

1. Create a namespace for the gateway:

   kubectl 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.yaml 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.

   secret-reader.yaml

   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:

   kubectl apply -f secret-reader.yaml

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

   gateway-deployment.yaml

   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
         labels:
           istio: <gateway_name>
           sidecar.istio.io/inject: "true"
       spec:
         containers:
           - name: istio-proxy
             image: auto
             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
         serviceAccountName: secret-reader
   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:

   kubectl apply -f gateway-deployment.yaml

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

   kubectl 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.yaml that contains the Kubernetes Service object for the gateway.

   gateway-service.yaml

   apiVersion: v1
   kind: Service
   metadata:
     name: <gateway_name>
     namespace: <gateway_namespace>
   spec:
     type: ClusterIP
     selector:
       istio: <gateway_name>
     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.
   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:

   kubectl apply -f gateway-service.yaml

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

   kubectl get endpoints <gateway_name> -n <gateway_namespace>

You should see output similar to the following example:

Example output

NAME              ENDPOINTS                                             AGE
<gateway_name>    10.131.0.181:15021,10.131.0.181:80,10.131.0.181:443   1m

10. Optional : Create a YAML file named gateway-hpa.yaml 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.

    gateway-hpa.yaml

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

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

    kubectl apply -f gateway-hpa.yaml

12. Optional : Create a YAML file named gateway-pdb.yaml 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.

    gateway-pdb.yaml

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

    kubectl apply -f gateway-pdb.yaml