App-of-apps & ApplicationSets

Manage many apps/clusters.

Managing dozens of Applications one YAML at a time does not scale, so Argo CD has two patterns for managing apps at scale. App-of-apps is a single parent Application whose source is a Git directory full of Application manifests — Argo CD syncs the parent, which creates all the child apps, so one bootstrap app manages a whole platform. It is simple and powerful: your entire set of apps is declared in Git and rolled out by syncing one root.

spec:
  source:
    repoURL: https://git.acme.internal/platform/apps.git
    path: applications/            # a directory of Application YAMLs
  destination: { server: https://kubernetes.default.svc, namespace: argocd }
  syncPolicy: { automated: { prune: true, selfHeal: true } }
# syncing this one app creates/manages every child Application in the directory

ApplicationSets

ApplicationSets go further: a controller that generates Applications from a template plus a generator. The list generator makes one app per entry; the cluster generator makes one per registered cluster; the Git generator makes one per directory or file in a repo; the matrix/merge generators combine them. This is how you deploy the same app to twenty clusters, or every team’s app from a monorepo, from a single templated definition — the answer to fleet-scale GitOps.

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
spec:
  generators:
    - clusters: {}                  # one Application per registered cluster
  template:
    metadata: { name: "monitoring-{{name}}" }
    spec:
      source: { repoURL: ..., path: monitoring, targetRevision: v2.1.0 }
      destination: { server: "{{server}}", namespace: monitoring }
      syncPolicy: { automated: { selfHeal: true } }