Doing More with the ApplicationSet

The whole point is varying things per cluster. Any field in the template can pull from an element key, so to make something differ between test and prod, you add a key to each element and reference it in the template.

Let's say you want one replica in test and three in prod. Add a replicas key to each element, then read it in a helm.parameters entry in the template:

cat < $HOME/web-appset.yaml
apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: web
  namespace: argocd
spec:
  generators:
  - list:
      elements:
      - cluster: test
        url: https://test-api.example:6443
        replicas: "1"
      - cluster: prod
        url: https://prod-api.example:6443
        replicas: "3"
  template:
    metadata:
      name: 'web-{{cluster}}'
    spec:
      project: default
      source:
        repoURL: $HELM_REPO_URL
        targetRevision: 0.2.0
        chart: web
        helm:
          # {{replicas}} pulls from each element. test gets "1", prod gets "3".
          parameters:
          - name: replicaCount
            value: '{{replicas}}'
      destination:
        server: '{{url}}'
        namespace: 'web-{{cluster}}'
      syncPolicy:
        syncOptions:
        - CreateNamespace=true
        automated:
          prune: true
          selfHeal: true
EOF

Now the two generated Applications differ in one more field:

web-test: server https://test-api.example:6443, namespace web-test, replicaCount 1.
web-prod: server https://prod-api.example:6443, namespace web-prod, replicaCount 3.

The element is a bag of key-value pairs, and you decide what each key drives. replicas here, but it could just as well feed a path, an image tag, a target revision, or any other template field. Keys you don't reference in the template are ignored, so there's no harm in carrying extra ones.

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