Managing multi-env deployments with ArgoCD ApplicationSets

2025-03-18gitops

We have five environments: dev, staging, preprod, prod-eu, prod-us. For a while we maintained one ArgoCD Application per service per environment — which meant around 80 Application manifests to keep in sync. It was fine until it wasn’t.

The problem

Updating a Helm values path required touching 16 files. Drift between environments was subtle and hard to catch. New services got inconsistent Application definitions depending on who set them up.

ApplicationSets to the rescue

ApplicationSets are a controller that generates ArgoCD Applications from a template plus a list of parameters. The List generator is the simplest:

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: my-service
spec:
  generators:
    - list:
        elements:
          - env: dev
            cluster: dev-cluster
            valuesFile: values-dev.yaml
          - env: prod-eu
            cluster: prod-eu-cluster
            valuesFile: values-prod.yaml
  template:
    metadata:
      name: "my-service-{{env}}"
    spec:
      project: default
      source:
        repoURL: https://github.com/org/helm-charts
        targetRevision: HEAD
        path: charts/my-service
        helm:
          valueFiles:
            - "{{valuesFile}}"
      destination:
        server: "{{cluster}}"
        namespace: my-service

What changed

One ApplicationSet per service. Adding a new environment is one line in the elements list. Structural changes to Application definitions happen in one place.

The Matrix generator is next on my list — combining cluster and app lists to generate the full cross-product automatically.