Introduction to Argo CD

This tutorial will walk you through implementing Argo CD with the Akuity Platform, to manage the deployment of the Helm charts in a declarative fashion.

Ultimately, you will have a Kubernetes cluster, with Applications deployed using an Argo CD control plane.

A video version of this tutorial is available with an introduction to Continous Delivery, GitOps, and Argo CD. 👇

• 1. Tutorial Scenario
• 2. Prerequisites
• 3. Setting up Your Environment
  • 3.1. Create the Repository from a Template
  • 3.2. Create a Kubernetes Cluster Using kind
  • 3.3. Launch an Argo CD Instance
  • 3.4. Deploy an Agent to the Cluster
• 4. Using Argo CD to Deploy Helm Charts
  • 4.1. Create an Application in Argo CD
  • 4.2. Syncing Changes Manually
  • 4.3. Enable Auto-sync and Self-heal for the Guestbook Application
  • 4.4. Demonstrate Application Auto-sync via Git
  • 4.5. Demonstrate Application Self-heal Functionality
• 5. Managing Argo CD Applications Declaratively
  • 5.1. Create an App of Apps
• 6. Review

1. Tutorial Scenario

To prepare for the tutorial, you can think of what to name your organization and environment. For example, your organization could be your GitHub username and your environment “staging”.

• You will use the organization name for creating an organization while setting up your account on the Akuity Platform.
• You will use the environment name for the cluster and the App of Apps Application in Argo CD.

In the tutorial steps, the text between less-than and greater-than symbols (i.e., <...>) indicates that you must substitute it with the value relevant to your scenario. For example, in the text https://github.com/<username>/intro-argo-cd-tutorial, you will replace <username> with your GitHub username.

2. Prerequisites

To follow this tutorial make sure you have minimal working knowledge of the following concepts:

• Kubernetes
• GitOps
• Argo CD
• Akuity Platform

The tutorial requires that you also have the following:

• a GitHub Account - you will use this to create the repo for the environment configuration and for creating an account on the Akuity Platform.
• the Kubernetes command-line tool, kubectl - will be used for interacting with the cluster directly.
• a Kubernetes cluster with Cluster Admin access (to create namespaces and cluster roles) or;
• Docker Desktop and kind installed on your local machine.
• egress traffic allowed from the Kubernetes cluster to the internet.

The tutorial was written and tested using the following tool and component versions:

• Argo CD: v2.5.1
• Docker Desktop: 4.13.1
• Kubernertes: v1.25.2
• kind: v0.16.0

3. Setting up Your Environment

3.1. Create the Repository from a Template

In this scenario, you manage the application Helm charts in version control. To represent this in the lab, you will create a repository from a template containing the application Helm charts.

1. Click this link or click "Use this template" from the akuity/intro-argo-cd-tutorial-template repo main page.

2. Ensure the desired "Owner" is selected (e.g., your account and not an organization).

3. Enter intro-argo-cd-tutorial for the "Repository name".

4. Then click Create repository from template.

Next, you have to update the placeholders:

1. Open the repo for editing.

tip

Changing github.com to github.dev in the URL will open up VSCode in your browser. From there, you can use the search and replace feature.

Throughout this tutorial, all repository changes can be done from your browser.

2. Search and replace <username> with your GitHub username.

       source:
   --    repoURL: 'https://github.com/<username>/intro-argo-cd-tutorial'
   ++    repoURL: 'https://github.com/myusername/intro-argo-cd-tutorial'

3. Search and replace <environment> with your environment name (e.g., staging).

       destination:
   --    name: <environment> # Update this value.
   ++    name: staging

4. Commit the changes to the main branch.

3.2. Create a Kubernetes Cluster Using kind

To deploy the application Helm charts during the lab, you will need a cluster. You could skip this section if you brought a cluster to the lab. Otherwise, you will create one on your local machine using kind.

1. Create a cluster using kind and specify your environment name.

   kind create cluster --name <environment>

   You should see the following output:

   Creating cluster "<environment>" ...
   ✓ Ensuring node image (kindest/node:v1.25.2) 🖼
   ✓ Preparing nodes 📦 📦 📦 📦  
   ✓ Writing configuration 📜 
   ✓ Starting control-plane 🕹️ 
   ✓ Installing CNI 🔌 
   ✓ Installing StorageClass 💾 
   ✓ Joining worker nodes 🚜 
   Set kubectl context to "kind-<environment>"
   You can now use your cluster with:
   
   kubectl cluster-info --context kind-<environment>
   
   Thanks for using kind! 😊

2. Check that the cluster works by running kubectl get nodes.

   % kubectl get nodes
   NAME                               STATUS   ROLES           AGE   VERSION
   <environment>-control-plane   Ready    control-plane   74s   v1.25.2

   Fetching the nodes will demonstrate that kubectl can connect to the cluster and query the API server. The node should be in the "Ready" status.

3.3. Launch an Argo CD Instance

This scenario demonstrates deploying applications to a cluster external to Argo CD.

Similar to how the GitHub repo is hosting the Helm charts, which describe what resources to deploy into Kubernetes, the Akuity Platform will host the Application manifests, which represent how to deploy the resources into the cluster. Along with Argo CD, which will implement the changes on the cluster.

1. Create an account on the Akuity Platform.

2. To log in with GitHub SSO, click "Continue with GitHub".

note

You can also use Google SSO or an email and password combo.

3. Click Authorize akuityio.

4. Create an organization by clicking create or join in the information bulletin.

5. In the top right, click New organization.

6. Enter your "Organization Name" and click Create.

7. At the top of the sidebar, click Argo CD.

8. In the top right, click Create.

9. Set the "Instance Name" to cluster-manager.

10. Click Create.

At this point, your Argo CD instance will begin initializing. The start-up typically takes under 2 minutes.

While the instance is initializing, you can prepare it for the rest of the lab.

1. In the dashboard for the Argo CD instance, click Settings.

2. In the "Declarative Management" section, click the Enabled toggle.

info

Declarative Management enables using the Akuity Platform with the App of Apps pattern (or ApplicationSets) by exposing the in-cluster destination. Using the in-cluster destination means an Application can create other Applications in the cluster hosting Argo CD. You will work on this later in the lab.

3. In the top right, click Save.

4. On the inner sidebar, under "Security & Access", click System Accounts.

5. Enable the "Admin Account" by clicking the toggle and clicking Confirm on the prompt.

6. Then, for the admin user, click Set Password.

7. Click Regenerate Password, then click Copy.

8. In the bottom right of the Set password prompt, hit Close.

9. In the top, next to the Argo CD instance name and status, click the instance URL (e.g., <instance-id>.cd.akuity.cloud) to open the Argo CD login page in a new tab.

10. Enter the username admin and the password copied previously.

You now have a fully-managed Argo CD instance 🎉

3.4. Deploy an Agent to the Cluster

You must connect the cluster to Argo CD to deploy the application resources. The Akuity Platform uses an agent-based architecture for connecting external clusters. So, you will provision an agent and deploy it to the cluster.

1. Back on the Akuity Platform, in the top left of the dashboard for the Argo CD instance, click Clusters.

2. In the top right, click Connect a cluster.

3. Enter your <environment> name as the "Cluster Name".

caution

Using the same chosen <environment> value as used when updating the repo is crucial because the manifests use this as the destination.name for Applications in Argo CD.

4. In the bottom right, click Connect Cluster.

5. To get the agent install command, click Copy to Clipboard. Then, in the bottom right, Done.

6. Open your terminal and check that your target is the correct cluster by running kubectl config current-context.

   If you are following along using kind, you should see the following:

   % kubectl config current-context
   kind-<env-name>

7. Paste and run the command against the cluster. The command will create the akuity namespace and deploy the resources for the Akuity Agent.

8. Check the pods in the akuity namespace. Wait for the Running status on all pods (approx. 1 minute).

   % kubectl get pods -n akuity
   NAME                                                        READY   STATUS    RESTARTS   AGE
   akuity-agent-<replicaset-id>-<pod-id>                       1/1     Running   0          65s
   akuity-agent-<replicaset-id>-<pod-id>                       1/1     Running   0          65s
   argocd-application-controller-<replicaset-id>-<pod-id>      2/2     Running   0          65s
   argocd-notifications-controller-<replicaset-id>-<pod-id>    1/1     Running   0          65s
   argocd-redis-<replicaset-id>-<pod-id>                       1/1     Running   0          65s
   argocd-repo-server-<replicaset-id>-<pod-id>                 1/1     Running   0          64s
   argocd-repo-server-<replicaset-id>-<pod-id>                 1/1     Running   0          64s

   Re-run the kubectl get pods -n akuity command to check for updates on the pod statuses.

9. Back on the Clusters dashboard, confirm that the cluster shows a green heart before the name, indicating a healthy status.

4. Using Argo CD to Deploy Helm Charts

4.1. Create an Application in Argo CD

Now, using an Application, you will declaratively tell Argo CD how to deploy the Helm charts.

Start by creating an Application to deploy the guestbook Helm Chart from the repo.

1. Navigate to the Argo CD UI, and click NEW APP.

2. In the top right, click EDIT AS YAML.

3. Paste the contents of apps/guestbook.yaml from your repo.

info

This manifest describes an Application.

• The name of the Application is guestbook.
• The source is your repo with the Helm charts.
• The destination is the cluster connected by the agent.
• The sync policy will automatically create the namespace.

4. Click SAVE. At this point, the UI has translated the Application manifest into the corresponding fields in the wizard.

5. In the top left, click CREATE. The new app pane will close and show the card for the Application you created. The status on the card will show "Missing" and "OutOfSync".

6. Click on the Application card titled argocd/guestbook.

info

In this state, the Application resource tree shows the manifests generated from the source repo URL and path defined. You can click APP DIFF to see what manifests the Application rendered. Since auto-sync is disabled, the resources do not exist in the destination yet.

7. In the top bar, click SYNC then SYNCHRONIZE to instruct Argo CD to create the resources defined by the Application.

The resource tree will expand as the Deployment creates a ReplicaSet that makes a pod, and the Service creates an Endpoint and EndpointSlice. The Application will remain in the "Progressing" state until the pod for the deployment is running.

Afterwards, all the top-level resources (i.e., those rendered from the Application source) in the tree will show a green checkmark, indicating that they are synced (i.e., present in the cluster).

4.2. Syncing Changes Manually

An Application now manages the deployment of the guestbook Helm chart. So what happens when you want to deploy a new image tag?

Instead of running helm upgrade guestbook ./guestbook, you will trigger a sync of the Application.

1. Navigate to your repo on Github, and open the file guestbook/values.yaml.

   https://github.com/<username>/intro-argo-cd-tutorial/blob/main/guestbook/values.yaml

2. In the top right of the file, click the pencil icon to edit.

3. Update the image.tag to 0.2.0.

4. Click Commit changes....

5. Add a commit message. For example chore(guestbook): bump tag to 0.2.0.

6. Click Commit changes.

7. Switch to the Argo CD UI and go to the argocd/guestbook Application.

8. In the top right, click the REFRESH button to trigger Argo CD to check for any changes to the Application source and resources.

note

The default sync interval is 3 minutes. Any changes made in Git may not apply for up to 3 minutes.

9. In the top bar, click SYNC then SYNCHRONIZE to instruct Argo CD to deploy the changes.

Due to the change in the repo, Argo CD will detect that the Application is out-of-sync. It will template the Helm chart (i.e., helm template) and patch the guestbook deployment with the new image tag, triggering a rolling update.

4.3. Enable Auto-sync and Self-heal for the Guestbook Application

Now that you are using an Application to describe how to deploy the Helm chart into the cluster, you can configure the sync policy to automatically apply changes—removing the need for developers to manually trigger a deployment for changes that already made it through the approval processes.

1. In the top menu, click APP DETAILS.

2. Under the SYNC POLICY section, click ENABLE AUTO-SYNC and on the prompt, click OK.

3. Below that, on the right of "SELF HEAL", click ENABLE.

4. In the top right of the App Details pane, click the X to close it.

If the Application was out-of-sync, this would immediately trigger a sync. In this case, your Application is already in sync, so Argo CD made no changes.

4.4. Demonstrate Application Auto-sync via Git

With auto-sync enabled on the guestbook Application, changes made to the main branch in the repo will be applied automatically to the cluster. You will demonstrate this by updating the number of replicas for the guestbook deployment.

1. Navigate to your repo on Github, and open the file guestbook/values.yaml.

   https://github.com/<username>/intro-argo-cd-tutorial/blob/main/guestbook/values.yaml

2. In the top right of the file, click the pencil icon to edit.

3. Update the replicaCount to the 2 list.

4. In the top right, click Commit changes....

5. Add a commit message. For example chore(guestbook): scale to 2 replicas.

6. In the bottom left, click Commit changes.

7. Switch to the Argo CD UI and go to the argocd/guestbook Application.

8. In the top right, click the REFRESH button to trigger Argo CD to check for any changes to the Application source and resources.

You can view the details of the sync operation by, in the top menu, clicking SYNC STATUS. Here it will display, what "REVISION" it was for, what triggered it (i.e., "INITIATED BY: automated sync policy"), and the result of the sync (i.e., what resources changed).

4.5. Demonstrate Application Self-heal Functionality

In your organization, everyone has direct and privileged access to the cluster. Users may apply changes to the cluster outside of the repo due to the over-provisioned access. For example, applying a Helm chart change to the cluster without getting pushed to the repo first.

With self-heal enabled, Argo CD will reconcile any changes to the Application resources that deviate from the repo.

To demonstrate this:

1. From the guestbook Application page in the Argo CD UI:

2. Locate the guestbook deploy (i.e., Deployment) resource and click the three vertical dots on the right side of the card.

3. Then click Delete.

4. Enter the deployment name guestbook and click OK.

Almost as quickly as you delete it, Argo CD will detect that the deploy resource is missing from the Application. It will briefly display the yellow circle with a white arrow to indicate that the resource is out-of-sync. Then automatically recreate it, bringing the Application back to a healthy status.

5. Managing Argo CD Applications Declaratively

5.1. Create an App of Apps

One of the benefits of using Argo CD is that you are now codifying the deployment process for the Helm charts in the Application spec.

Earlier in the lab, you created the guestbook Application imperatively, using the UI. But what if you want to manage the Application manifests declaratively too? This is where the App of Apps pattern comes in.

1. Navigate to the Applications dashboard in the Argo CD UI, and click NEW APP.

2. In the top right, click EDIT AS YAML.

3. Paste the contents of app-of-apps.yaml (in the repo's root).

   apiVersion: argoproj.io/v1alpha1
   kind: Application
   metadata:
     name: applications
     namespace: argocd
   spec:
     destination:
       name: in-cluster
     project: default
     source:
       path: apps
       repoURL: https://github.com/<username>/intro-argo-cd-tutorial # Update to your repo URL.
       targetRevision: HEAD

   This Application will watch the apps/ directory in your repo which contains Application manifests for the guestbook and portal Helm charts.

4. Click SAVE.

5. Then, in the top left, click CREATE.

6. Click on the Application card titled argocd/applications.

   At this point, the Application will be out-of-sync. The diff will show the addition of the argocd.argoproj.io/tracking-id label to the existing guestbook Application, which indicates that the "App of Apps now manages it".

     kind: Application
     metadata:
   ++  annotations:
   ++    argocd.argoproj.io/tracking-id: 'applications:argoproj.io/Application:argocd/guestbook'
       generation: 44
       labels:
         ...
         path: guestbook
         repoURL: 'https://github.com/<username>/intro-argo-cd-tutorial'
       syncPolicy:
         automated: {}

   Along with a new Application for the portal Helm chart.

7. To apply the changes, in the top bar, click SYNC then SYNCHRONIZE.

From this Application, you can see all of the other Applications managed by it in the resource tree. Each child Application resource has a link to its view on the resource card.

6. Review

You have reached the end of the tutorial. You have an Argo CD instance deploying Helm charts from your repo into your cluster.

You no longer manually deploy Helm chart changes. The Application spec describes the process for deploying the Helm charts declaratively. There's no longer a need for direct access to the cluster, removing the primary source of configuration drift.