A Beginner's Guide to Getting Started with ArgoCD: A Step-by-Step Tutorial

DevOpshelian's photo
DevOpshelian
·

6 min read

In the rapidly evolving landscape of DevOps, automation is key to managing complex infrastructure and application deployments. ArgoCD, a declarative continuous delivery tool for Kubernetes, has gained immense popularity for simplifying GitOps workflows. With ArgoCD, developers can manage their Kubernetes applications using Git as the single source of truth, ensuring consistency, scalability, and automation in the deployment pipeline.

In this tutorial, we will take a hands-on approach to learning ArgoCD. By the end of this guide, you will understand how to install ArgoCD, configure it, and deploy a sample application to a Kubernetes cluster using GitOps principles.

Prerequisites

Before we dive into the tutorial, ensure you have the following prerequisites:

- A Kubernetes cluster (You can use a local setup like Minikube or a managed cluster like Google Kubernetes Engine or Amazon EKS)
- `kubectl` command-line tool installed and configured to interact with your Kubernetes cluster
- Basic knowledge of Kubernetes and Git
- A GitHub account for hosting your Git repository

Step 1: Install ArgoCD on Your Kubernetes Cluster

The first step is to install ArgoCD in your Kubernetes cluster. ArgoCD provides a Kubernetes-native way to deploy and manage your applications.

1. Create the ArgoCD namespace:

Run the following command to create a dedicated namespace for ArgoCD:

kubectl create namespace argocd

2. Install ArgoCD using the manifests:

To install ArgoCD, use the official installation manifests provided by the ArgoCD team. Apply the following command:

kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/install.yaml

This will install ArgoCD and its associated components in the `argocd` namespace.

3. Verify the installation:

Ensure all the ArgoCD components are up and running by checking the pods in the `argocd` namespace:

kubectl get pods -n argocd

You should see multiple pods running, including `argocd-server`, `argocd-repo-server`, `argocd-application-controller`, and `argocd-dex-server`.

Step 2: Access the ArgoCD Web UI

ArgoCD provides a web-based interface that makes it easy to visualize and manage your deployments.

1. Expose the ArgoCD Server:

By default, the ArgoCD server is not exposed externally. You can access it by creating a port-forward:

kubectl port-forward svc/argocd-server -n argocd 8080:443

This command forwards your local port `8080` to the ArgoCD server's port `443`, allowing you to access the ArgoCD UI locally.

2. Access the UI:

Open your web browser and navigate to `https://localhost:8080`. You will be prompted to log in.

3. Retrieve the initial password:

The initial admin password is stored as a Kubernetes secret. Retrieve it using the following command:

kubectl get secret argocd-initial-admin-secret -n argocd -o jsonpath="{.data.password}" | base64 -d

Use `admin` as the username and the retrieved password to log in.

Step 3: Configure a GitOps Workflow with ArgoCD

Now that ArgoCD is up and running, let’s set up a GitOps workflow. In this example, we'll deploy a simple Nginx application to our Kubernetes cluster using ArgoCD.

1. Create a Git repository:

Set up a new Git repository on GitHub (or any Git hosting service). This repository will store your Kubernetes manifests. Initialize it with a basic `nginx` deployment and service configuration. Below is a simple example of what your Kubernetes manifest might look like:

# nginx-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:latest
          ports:
            - containerPort: 80

# nginx-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: LoadBalancer

2. Add the application to ArgoCD:

In ArgoCD, applications represent your deployed Kubernetes resources. To create an application, either use the CLI or the Web UI. Here’s how to do it via the CLI:

argocd app create nginx-app \
--repo <YOUR_REPO_URL> \
--path ./ \
--dest-server https://kubernetes.default.svc \
--dest-namespace default

Replace `<YOUR_REPO_URL>` with the URL of your Git repository containing the Nginx manifests.

3. Sync the application:

ArgoCD will automatically detect changes in your Git repository and apply them to the cluster. To trigger a sync manually, use the following command:

argocd app sync nginx-app

You can also perform this action via the ArgoCD Web UI by navigating to your application and clicking the "Sync" button.

4. Monitor the deployment:

You can monitor the status of your deployment through the ArgoCD Web UI. If everything is configured correctly, you should see your Nginx application deployed and running in your Kubernetes cluster.

Step 4: Automate Application Sync

ArgoCD supports automatic synchronization of your applications whenever changes are detected in the Git repository. To enable auto-sync for your application, you can configure it as follows:

1. Enable auto-sync:

Use the CLI or the Web UI to enable auto-sync on your application. Here’s how to do it using the CLI:

argocd app set nginx-app --sync-policy automated

This ensures that ArgoCD will automatically sync your application whenever changes are pushed to the Git repository.

2. Verify auto-sync:

Push a change to your Git repository, such as updating the number of replicas for the Nginx deployment, and watch ArgoCD automatically sync and apply the changes to your cluster.

Step 5: Manage Rollbacks and History

One of the key advantages of using GitOps with ArgoCD is the ability to track and roll back deployments based on Git history. Here’s how you can manage rollbacks in ArgoCD:

1. Identify the Target Commit:
 — Every deployment in ArgoCD is based on a specific commit in your Git repository. To roll back a deployment, you need to identify the commit hash of the version you want to revert to.
 — Use `git log` or your Git provider’s UI to locate the commit that represents the stable version of your application.

2. Sync to the Desired Commit:
 — In the ArgoCD UI, navigate to the application that you want to roll back.
 — Click on the **History and Rollback** tab. This will display the history of all previous sync operations, along with their corresponding Git commits.
 — Select the desired commit that you wish to roll back to and click **Rollback**. ArgoCD will automatically update the Kubernetes cluster to match the state defined in that commit.

3. Manual Rollback via Git:
 — Another approach is to revert the changes directly in your Git repository. You can use the `git revert` command to reverse specific commits and push the changes to the repository. ArgoCD will detect the new commit and automatically sync your cluster to the reverted state.
 — For example:

git revert 
git push origin main

— This method allows you to handle rollbacks purely through Git, ensuring that the source of truth remains in the repository.

4. Automated Rollbacks:
 — You can also configure automated rollbacks using ArgoCD in conjunction with monitoring tools like Prometheus or Datadog. By setting up health checks and alerting systems, you can trigger automated rollbacks when a deployment fails health checks or if performance metrics fall below a certain threshold.
 — This is particularly useful in CI/CD pipelines where rapid recovery from failed deployments is critical.

5. Monitor the Rollback Process:
 — Once a rollback is initiated, ArgoCD will start updating the Kubernetes resources to match the desired state. You can monitor the progress through the ArgoCD UI or use the ArgoCD CLI to check the status of the deployment.
 — Run the following command to see the status:

argocd app get

6. Verify the Rollback:
 — After the rollback is complete, ensure that the application is functioning as expected. This may involve checking logs, running integration tests, or validating the application’s behavior through monitoring tools.
 — Once verified, update your Git repository with any necessary configuration changes to prevent further issues.

By effectively managing rollbacks and tracking history through Git, ArgoCD provides a powerful mechanism for maintaining stability in your Kubernetes environments. It ensures that you can easily revert to previous versions of your applications and keep your infrastructure in sync with your desired state, all while leveraging the power of GitOps.

ArgoCDDevops