ArgoCD App of Apps with Heml on Kubernetes

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Introduction

Here are the files we'll use in this post:

charts
├── apps
│   ├── Chart.yaml
│   ├── templates
│   │   ├── argo-cd.yaml
│   │   ├── prometheus.yaml
│   │   └── root.yaml
│   └── values.yaml
└── argo-cd
    ├── Chart.lock
    ├── Chart.yaml
    ├── charts
    │   └── argo-cd-2.11.0.tgz
    ├── templates
    └── values.yaml

Let's make our working directory, charts:

$ mkdir -p charts

We'll create our own Helm "umbrella" chart that pulls in the original Argo CD chart as a dependency.

Create argo-cd chart and delete files under "argo-cd/templates/":

$ helm create argo-cd

$ rm -rf argo-cd/templates/*

Then, repalce the contents of the following two files.

charts/argo-cd/Chart.yaml:

apiVersion: v2
name: argo-cd
version: 1.0.0
dependencies:
  - name: argo-cd
    version: 2.11.0
    repository: https://argoproj.github.io/argo-helm

charts/argo-cd/values.yaml:

argo-cd:
  installCRDs: false
  global:
    image:
      tag: v1.8.1
  dex:
    enabled: false
  server:
    extraArgs:
      - --insecure
    config:
      repositories: |
        - type: helm
          name: stable
          url: https://charts.helm.sh/stable
        - type: helm
          name: argo-cd
          url: https://argoproj.github.io/argo-helm

Add the helm repo and update the dependency:

$ helm repo add argo-cd https://argoproj.github.io/argo-helm
$ helm dep update charts/argo-cd/

$ git push -u origin main

Installing ArgoCD and accessing ArgoCD API Server

Let's install ArgoCD into the default namespace:

$ helm install argo-cd charts/argo-cd/

$ kubectl get pods
NAME                                                     READY   STATUS    RESTARTS   AGE
argo-cd-argocd-application-controller-7f9c6b77d7-4zc2v   1/1     Running   0          3m14s
argo-cd-argocd-redis-54487756bf-sfz5f                    1/1     Running   0          3m14s
argo-cd-argocd-repo-server-5b74c5fd5c-j88tm              1/1     Running   0          3m14s
argo-cd-argocd-server-5fd4f6c7cd-l8xqp                   1/1     Running   0          3m14s

Once the pods are ready, ArgoCD will be running. But the ArgoCD API server will not be accessible from outside the cluster. We'll use port-forward to expose a port to the service, and forward it to localhost:

$ kubectl port-forward svc/argo-cd-argocd-server 8080:443  
Forwarding from 127.0.0.1:8080 -> 8080
Forwarding from [::1]:8080 -> 8080

Now we'll be able to access the API server via localhost:8080:

The username for Argo CD is admin and the initial password is autogenerated. The initial password is usually the pod name of the Argo CD server.

App of Apps - a root ArgoCD Application

the App of Apps Pattern lets us define a root ArgoCD Application. So, rather than point to an application manifest, the Root App points to a folder which contains the Application YAML definition for each microservice (child App). Each microservice's Application YAML then points to a directory containing the application manifests.

The root application has one task: it generates Application manifests for other applications. ArgoCD will watch the root application and synchronize any applications that it generates.

Let's create a Helm chart for the Root App that has Application manifests as templates.

We'll create it in an apps directory and put a Chart.yaml file and an empty values.yaml file in it:

$ mkdir -p apps/templates
$ touch apps/values.yaml

apps/Chart.yaml:

apiVersion: v2
name: root
version: 1.0.0

Now,finally, Application manifest for our root application in apps/templates/root.yaml. This allows us to do any updates to the root application itself through Argo CD:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: root
  finalizers:
  - resources-finalizer.argocd.argoproj.io
spec:
  destination:
    server: https://kubernetes.default.svc
    namespace: default
  project: default
  source:
    path: apps/
    repoURL: https://github.com/arthurk/argocd-example-install.git
    targetRevision: HEAD
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

The Application watches the Helm chart under apps/ (root application) and synchronizes it if changes were detected.

Argo CD looks for a Chart.yaml file under path. If present, it will check the apiVersion inside it and for v2 it uses Helm 3 to render the chart. Actually, ArgoCD will not use helm install to install charts. It will render the chart with helm template and then apply the output with kubectl.

To deploy the root application, we need to push the files to our Git repository and apply the manifest:

$ git add apps
$ git commit -m "add apps"
$ git push -u origin main    

$ helm template apps/ | kubectl apply -f -
application.argoproj.io/root created

$ tree ../charts
../charts
├── apps
│   ├── Chart.yaml
│   ├── templates
│   │   └── root.yaml
│   └── values.yaml
└── argo-cd
    ├── Chart.lock
    ├── Chart.yaml
    ├── charts
    │   └── argo-cd-2.11.0.tgz
    ├── templates
    └── values.yaml

Earlier, we installed Argo CD with helm install which means that updates would require us to run helm upgrade. To avoid doing this we can create an Application resource for Argo CD and let it manage itself so that any updates to our Argo CD deployment can be made by modifying files in our Git repository rather than running manual commands.

We put the application manifest in apps/templates/argo-cd.yaml:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: argo-cd
  namespace: default
  finalizers:
  - resources-finalizer.argocd.argoproj.io
spec:
  destination:
    server: https://kubernetes.default.svc
    namespace: default
  project: default
  source:
    path: charts/argo-cd
    repoURL: https://github.com/arthurk/argocd-example-install.git
    targetRevision: HEAD
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

Push the file to our Git repository:

$ vi apps/templates/argo-cd.yaml
$ git add apps/templates/argo-cd.yaml
$ git commit -m "add argo-cd application"

Installing prometheus

To see how to deploy a Helm chart with ArgoCD, we'll add Prometheus on our cluster.

Let's add the application manifest in apps/templates/prometheus.yaml:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: prometheus
  namespace: default
  finalizers:
  - resources-finalizer.argocd.argoproj.io
spec:
  destination:
    server: https://kubernetes.default.svc
    namespace: default
  project: default
  source:
    chart: prometheus
    helm:
      values: |
        pushgateway:
          enabled: false
    repoURL: https://prometheus-community.github.io/helm-charts
    targetRevision: 13.0.2
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

To deploy the application we need push the manifest to our repository:

$ git add apps/templates/prometheus.yaml
$ git commit -m "add prometheus app"
$ git push origin main

???: the Promethues is supposed to show up in the UI, but it's not. I'll comback to this later.

So, we have to use the following:

├── apps
│   ├── Chart.yaml
│   ├── templates
│   │   ├── argo-cd.yaml
│   │   ├── prometheus.yaml
│   │   └── root.yaml
│   └── values.yaml
└── argo-cd
    ├── Chart.lock
    ├── Chart.yaml
    ├── charts
    │   └── argo-cd-2.11.0.tgz
    ├── templates
    └── values.yaml    
    
$ helm template apps/ | kubectl apply -f -
application.argoproj.io/argo-cd configured
application.argoproj.io/prometheus created
application.argoproj.io/root configured