app-of-apps.md

Organizing and Managing Argo CD Apps through app-of-apps

Learning Goals

• Create a bootstrap app manifest
• Arrange Argo CD app manifests in a folder structure

Introduction

In this exercise, we will work on organizing and managing Argo CD applications more effectively. We will create a bootstrap app manifest to serve as a starting point, structure our repository to accommodate multiple apps, and work with a new app manifest for a Helm chart.

Exercise

Overview

• Create Bootstrap App Manifest
• Create Folder for All Apps
• Move Jenkins App Manifest
• Create the App Manifest for the Quotes Helm Chart

Step by step instructions

More Details

• Create bootsrap app manifest
• Create folder for all apps in the repo
• Move Jenkins app manifest to the folder
• Create the app manifest for the quotes helm chart located in the same repo. (OR IN THE OTHER REPO TODO)
  • Enable sync policy, prune and self-heal
• kubectl delete parent app, make sure nothing is there. kubectl apply parent app again.

Step 1: Create Bootstrap App Manifest

1. On your workstation vs-code:
2. Create a file named bootstrap-app.yaml anywhere, with the following content:

💡 NB! Make sure to replace the placeholders with your own values.

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: bootstrap-student-<YOURNUMBER>
  namespace: argocd
  finalizers:
    - resources-finalizer.argocd.argoproj.io
spec:
  destination:
    server: https://kubernetes.default.svc
    namespace: student-<YOURNUMBER>
  project: default
  source:
    repoURL: <YOUR GITHUB REPO>
    targetRevision: HEAD
    path: apps
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

1. Apply the bootstrap app manifest to your cluster:

kubectl apply -f bootstrap-app.yaml

1. Go to the Argo CD UI and verify that the bootstrap app is present. It should have an error saying that it cannot find the apps folder. This is expected.

Step 2: Create Folder for All Apps, and add Jenkins App Manifest to it.

Save the current application manifest to your repository in a new folder named apps.

• Get the Jenkins application manifest from the Argo CD UI:
  • click App details and then Manifest.
  • It does not have the entire manifest, but it has the spec part.
  • It should be saved in the apps directory in your repository.
  • Name it jenkins-app.yaml.

💡 Help me out

The file that you will be saving looks like this, with the <NUMBER> being your student number and <YOUR GIT REPO> being your repository URL:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: <YourName>-jenkins
  namespace: argocd
  finalizers:
    - resources-finalizer.argocd.argoproj.io
spec:
  project: default
  sources:
  - repoURL: 'https://charts.bitnami.com/bitnami'
    targetRevision: 12.4.0
    helm:
      valueFiles:
        - $values/jenkins/values.yaml
    chart: jenkins
  - repoURL: 'https://github.com/<YOUR GIT REPO>/argocd-katas'
    targetRevision: main
    ref: values
  destination:
    server: 'https://kubernetes.default.svc'
    namespace: student-<NUMBER>
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

• Add, commit and push the jenkins-app.yaml to the repository.
• Go to the Argo CD UI and verify that the bootstrap app is present. It should now be updated to include the apps folder, and therefore the Jenkins app manifest.

Now the jenkins app is connected with the bootstrap app.

Delete the jenkins app

• In the Argo CD UI, delete the jenkins app.
• What happens when you do that?

Create the App Manifest for the Quotes Helm Chart

1. In the apps folder, create a file named quotes-app.yaml with the following content:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: quotes-student-<YOURNUMBER>
  namespace: argocd
  finalizers:
    - resources-finalizer.argocd.argoproj.io
spec:
  destination:
    server: https://kubernetes.default.svc
    namespace: student-<YOUR number>
  project: default
  source:
    repoURL: https://github.com/eficode-academy/argocd-katas.git  # Update this URL if the helm chart is in a different repo
    targetRevision: HEAD
    path: quotes-flask/helm/quotes-flask
    helm:
      valueFiles:
        - values.yaml
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

• Click refresh in the Argo CD UI. The quotes app should now be present as an application in Argo CD.
• Click on the quotes app to see all the resources that it creates.

Apply and Re-Apply the Bootstrap App

1. Verify the applications are synced and running as expected.

2. Delete the bootstrap app from your cluster:

kubectl delete -f bootstrap-app.yaml

1. Verify that the applications and resources are removed.

kubectl get all

1. Re-apply the bootstrap app manifest to your cluster:

kubectl apply -f bootstrap-app.yaml

1. Verify the applications are synced and running as expected again.

You have now seen how fast it is to reapply your manifests to the cluster. This is a great way to recover from a disaster, or to make sure that your cluster is in the desired state.

Conclusion

In this exercise, you learned how to organize Argo CD app manifests within a repository, create a new app manifest for a Helm chart, and utilize sync, prune, and self-heal features to maintain the desired state in your Kubernetes cluster. This structure and practices will help you manage and operate your applications more effectively with Argo CD.