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Setup

We'll create templates for a set of ArgoCD applications using the DRY (Don't Repeat Yourself) approach with Helm charts:

.
|-- app-of-apps
|   |-- Chart.yaml
|   |-- templates
|   |   |-- _application.yaml
|   |   `-- application.yaml
|   `-- values.yaml
|-- ui
`-- catalog
    ...

The _application.yaml is a template file which will be used to dynamically create applications based on a list of component names:

~/environment/eks-workshop/modules/automation/gitops/argocd/app-of-apps/templates/_application.yaml
{{- define "application" -}}
{{- $root:= . }}
{{- range $application := .Values.applications}}
---
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: {{  $application.name }}
  namespace: argocd
  finalizers:
    - resources-finalizer.argocd.argoproj.io
  labels:
    app.kubernetes.io/created-by: eks-workshop
spec:
  project: default
  destination:
    server: {{ $root.Values.spec.destination.server }}
    namespace: {{  $application.name }}
  source:
    repoURL: {{ $root.Values.spec.source.repoURL }}
    targetRevision: {{ $root.Values.spec.source.targetRevision }}
    path: {{  $application.name }}
  syncPolicy:
    syncOptions:
    - CreateNamespace=true
    automated:
      prune: true
      selfHeal: true
{{- end -}}
{{- end -}}

The values.yaml file specifies a list of components for which ArgoCD applications will be generated, as well as configuration related to the Git repository that will be common across all applications:

~/environment/eks-workshop/modules/automation/gitops/argocd/app-of-apps/values.yaml
spec:
  destination:
    server: https://kubernetes.default.svc
  source:
    repoURL: ${GITOPS_REPO_URL_ARGOCD}
    targetRevision: main

applications:
  - name: carts
  - name: catalog
  - name: checkout
  - name: orders
  - name: ui

First, let's copy this foundational App of Apps configuration to our Git directory:

~$cp -R ~/environment/eks-workshop/modules/automation/gitops/argocd/app-of-apps ~/environment/argocd/
~$yq -i ".spec.source.repoURL = env(GITOPS_REPO_URL_ARGOCD)" ~/environment/argocd/app-of-apps/values.yaml


Now, let's commit and push these changes to the Git repository:


~$git -C ~/environment/argocd add .
~$git -C ~/environment/argocd commit -am "Adding App of Apps"
~$git -C ~/environment/argocd push


Next, we need to create a new Argo CD Application to implement the App of Apps pattern. While doing this, we'll enable ArgoCD to automatically synchronize the state in the cluster with the configuration in the Git repository using the --sync-policy automated flag:


~$argocd app create apps --repo $GITOPS_REPO_URL_ARGOCD \
  --dest-server https://kubernetes.default.svc \
  --sync-policy automated --self-heal --auto-prune \
  --set-finalizer \
  --upsert \
  --path app-of-apps
 application 'apps' created
~$argocd app wait apps --timeout 120


Open the Argo CD UI and navigate to the main "Applications" page. Our App of Apps configuration has been deployed and synced, but except for the UI component, all of the workload apps are marked as "Unknown".


argocd-ui-apps.png


We will deploy the configurations for the workloads in the next step.