Getting Started - AWS Load Balancer Controller

This guide covers how Argo Rollouts integrates with the AWS Load Balancer Controller for traffic shaping. This guide builds upon the concepts of the basic getting started guide.

Requirements

• Kubernetes cluster with AWS ALB Ingress Controller installed

Tip

See the Load Balancer Controller Installation instructions on how to install the AWS Load Balancer Controller

1. Deploy the Rollout, Services, and Ingress

When an AWS ALB Ingress is used as the traffic router, the Rollout canary strategy must define the following fields:

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: rollouts-demo
spec:
  strategy:
    canary:
      # canaryService and stableService are references to Services which the Rollout will modify
      # to target the canary ReplicaSet and stable ReplicaSet respectively (required).
      canaryService: rollouts-demo-canary
      stableService: rollouts-demo-stable
      trafficRouting:
        alb:
          # The referenced ingress will be injected with a custom action annotation, directing
          # the AWS Load Balancer Controller to split traffic between the canary and stable
          # Service, according to the desired traffic weight (required).
          ingress: rollouts-demo-ingress
          # Reference to a Service that the Ingress must target in one of the rules (optional).
          # If omitted, uses canary.stableService.
          rootService: rollouts-demo-root
          # Service port is the port which the Service listens on (required).
          servicePort: 443
...

The Ingress referenced by the Rollout must have a rule which matches one of Rollout services. This should be canary.trafficRouting.alb.rootService (if specified), otherwise the rollout will use canary.stableService.

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: rollouts-demo-ingress
  annotations:
    kubernetes.io/ingress.class: alb
spec:
  rules:
  - http:
      paths:
      - path: /*
        backend:
          # serviceName must match either: canary.trafficRouting.alb.rootService (if specified),
          # or canary.stableService (if rootService is omitted)
          serviceName: rollouts-demo-root
          # servicePort must be the value: use-annotation
          # This instructs AWS Load Balancer Controller to look to annotations on how to direct traffic
          servicePort: use-annotation

During an update, the Ingress will be injected with a custom action annotation, which directs the ALB to splits traffic between the stable and canary Services referenced by the Rollout. In this example, those Services are named: rollouts-demo-stable and rollouts-demo-canary respectively.

Run the following commands to deploy:

• A Rollout
• Three Services (root, stable, canary)
• An Ingress

kubectl apply -f https://raw.githubusercontent.com/argoproj/argo-rollouts/master/docs/getting-started/alb/rollout.yaml
kubectl apply -f https://raw.githubusercontent.com/argoproj/argo-rollouts/master/docs/getting-started/alb/services.yaml
kubectl apply -f https://raw.githubusercontent.com/argoproj/argo-rollouts/master/docs/getting-started/alb/ingress.yaml

After applying the manifests you should see the following rollout, services, and ingress resources in the cluster:

$ kubectl get ro
NAME            DESIRED   CURRENT   UP-TO-DATE   AVAILABLE
rollouts-demo   1         1         1            1

$ kubectl get svc
NAME                   TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
rollouts-demo-root     NodePort    10.100.16.123    <none>        80:30225/TCP   2m43s
rollouts-demo-canary   NodePort    10.100.16.64     <none>        80:30224/TCP   2m43s
rollouts-demo-stable   NodePort    10.100.146.232   <none>        80:31135/TCP   2m43s

$ kubectl get ingress
NAME                    HOSTS   ADDRESS                                                                       PORTS   AGE
rollouts-demo-ingress   *       b0548428-default-rolloutsd-6951-1972570952.ap-northeast-1.elb.amazonaws.com   80      6m36s

kubectl argo rollouts get rollout rollouts-demo

2. Perform an update

Update the rollout by changing the image, and wait for it to reach the paused state.

kubectl argo rollouts set image rollouts-demo rollouts-demo=argoproj/rollouts-demo:yellow
kubectl argo rollouts get rollout rollouts-demo

At this point, both the canary and stable version of the Rollout are running, with 5% of the traffic directed to the canary. To understand how this works, inspect the listener rules for the ALB. When looking at the listener rules, we see that the forward action weights have been modified by the controller to reflect the current weight of the canary.

The controller has added rollouts-pod-template-hash selector to the Services and attached the same label to the Pods. Therefore, you can split the traffic by simply forwarding the requests to the Services according to the weights.

As the Rollout progresses through steps, the forward action weights will be adjusted to match the current setWeight of the steps.