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Traffic splitting with Application Gateway for Containers - Gateway API

This document helps set up an example application that uses the following resources from Gateway API:

  • Gateway - creating a gateway with one http listener
  • HTTPRoute - creating an HTTP route that references two backend services having different weights

Background

Application Gateway for Containers enables you to set weights and shift traffic between different backend targets. See the following example scenario:

A figure showing traffic splitting with Application Gateway for Containers.

Prerequisites

  1. If following the BYO deployment strategy, ensure you set up your Application Gateway for Containers resources and ALB Controller.

  2. If following the ALB managed deployment strategy, ensure you have provisioned your ALB Controller and provisioned the Application Gateway for Containers resources via the ApplicationLoadBalancer custom resource.

  3. Deploy sample HTTP application:
    Apply the following deployment.yaml file on your cluster to create a sample web application to demonstrate traffic splitting / weighted round robin support.

    kubectl apply -f https://raw.githubusercontent.com/MicrosoftDocs/azure-docs/refs/heads/main/articles/application-gateway/for-containers/examples/traffic-split-scenario/deployment.yaml

    This command creates the following on your cluster:

    • A namespace called test-infra
    • Two services called backend-v1 and backend-v2 in the test-infra namespace
    • Two deployments called backend-v1 and backend-v2 in the test-infra namespace

Deploy the required Gateway API resources

Create a gateway:

kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: gateway-01
  namespace: test-infra
  annotations:
    alb.networking.azure.io/alb-namespace: alb-test-infra
    alb.networking.azure.io/alb-name: alb-test
spec:
  gatewayClassName: azure-alb-external
  listeners:
  - name: http
    port: 80
    protocol: HTTP
    allowedRoutes:
      namespaces:
        from: Same
EOF

Note

When the ALB Controller creates the Application Gateway for Containers resources in Azure Resource Manager, it uses the following naming convention for a frontend resource: fe-<eight randomly generated characters>.

If you want to change the name of the frontend resource created in Azure, consider following the bring-your-own deployment strategy.

Once the gateway resource is created, ensure the status is valid, the listener is Programmed, and an address is assigned to the gateway.

kubectl get gateway gateway-01 -n test-infra -o yaml

Example output of successful gateway creation.

status:
  addresses:
  - type: Hostname
    value: xxxx.yyyy.alb.azure.com
  conditions:
  - lastTransitionTime: "2023-06-19T21:04:55Z"
    message: Valid Gateway
    observedGeneration: 1
    reason: Accepted
    status: "True"
    type: Accepted
  - lastTransitionTime: "2023-06-19T21:04:55Z"
    message: Application Gateway For Containers resource has been successfully updated.
    observedGeneration: 1
    reason: Programmed
    status: "True"
    type: Programmed
  listeners:
  - attachedRoutes: 0
    conditions:
    - lastTransitionTime: "2023-06-19T21:04:55Z"
      message: ""
      observedGeneration: 1
      reason: ResolvedRefs
      status: "True"
      type: ResolvedRefs
    - lastTransitionTime: "2023-06-19T21:04:55Z"
      message: Listener is accepted
      observedGeneration: 1
      reason: Accepted
      status: "True"
      type: Accepted
    - lastTransitionTime: "2023-06-19T21:04:55Z"
      message: Application Gateway For Containers resource has been successfully updated.
      observedGeneration: 1
      reason: Programmed
      status: "True"
      type: Programmed
    name: gateway-01-http
    supportedKinds:
    - group: gateway.networking.k8s.io
      kind: HTTPRoute

Once the gateway is created, create an HTTPRoute

kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: traffic-split-route
  namespace: test-infra
spec:
  parentRefs:
  - name: gateway-01
  rules:
  - backendRefs:
    - name: backend-v1
      port: 8080
      weight: 50
    - name: backend-v2
      port: 8080
      weight: 50
EOF

Once the HTTPRoute resource is created, ensure the route is Accepted and the Application Gateway for Containers resource is Programmed.

kubectl get httproute traffic-split-route -n test-infra -o yaml

Verify the status of the Application Gateway for Containers resource has been successfully updated.

status:
  parents:
  - conditions:
    - lastTransitionTime: "2023-06-19T22:18:23Z"
      message: ""
      observedGeneration: 1
      reason: ResolvedRefs
      status: "True"
      type: ResolvedRefs
    - lastTransitionTime: "2023-06-19T22:18:23Z"
      message: Route is Accepted
      observedGeneration: 1
      reason: Accepted
      status: "True"
      type: Accepted
    - lastTransitionTime: "2023-06-19T22:18:23Z"
      message: Application Gateway For Containers resource has been successfully updated.
      observedGeneration: 1
      reason: Programmed
      status: "True"
      type: Programmed
    controllerName: alb.networking.azure.io/alb-controller
    parentRef:
      group: gateway.networking.k8s.io
      kind: Gateway
      name: gateway-01
      namespace: test-infra

Test Access to the Application

Now we're ready to send some traffic to our sample application, via the FQDN assigned to the frontend. Use the following command to get the FQDN:

fqdn=$(kubectl get gateway gateway-01 -n test-infra -o jsonpath='{.status.addresses[0].value}')

Curling this FQDN should return responses from the backends/pods as configured on the HTTPRoute.

# this curl command will return 50% of the responses from backend-v1
# and the remaining 50% of the responses from backend-v2
watch -n 1 curl http://$fqdn

Congratulations, you have installed ALB Controller, deployed a backend application and routed traffic to the application via the ingress on Application Gateway for Containers.