How to install ArgoCD on Kubernetes cluster?

Kubernetes became one of the de facto standards for containerized applications. Many cloud platforms from the smallest to the largest like Scaleway, DigitalOcean, AWS, Google Cloud, Azure and IBM Cloud now provide managed services for Kubernetes. Creating a cluster and deploying an application into it became so easy that it takes a couple of minutes to run your application on it. As these companies abstract the architecture layer from the developer that you do not need to maintain a cluster anymore, deployment of the application became the new main focus. There are many open-source tools that help you to deploy your application on clusters. In my opinion, one of the most famous ones is Argo CD. In this tutorial, we will install Argo CD on a cluster, login to UI and deploy an application with it.

What is Argo CD

Argo CD is a lightweight and easy to configure declarative GitOps tool. It is built to deploy applications to Kubernetes. As continuous delivery (CD) has increasing popularity, Argo CD does provide many interesting capabilities. Unlike other CD tools, Argo CD is lightweight and easy to configure. It is purpose-built to deploy applications only to Kubernetes, it's UI does not have overhead UI tools. It's also built with a GitOps flow. Meaning, everything ArgoCD sees as its source of truth is stored in a repository with multiple branches for different purposes such as `canary` and `production`.

Requirements

In order to follow this tutorial, you need to have a basic understanding of the Kubernetes concept. You can have a look at Kubernetes documentation to understand `Deployment` and `Service` relation. You might need to understand the basic concept of GitOps logic for ArgoCD.

Prerequisites

Before you get started, you will need to have the following development environment:.

1. Kubernetes cluster.
2. `kubectl` installed. You will need it to manage your clusters.
3. Have a kubeconfig file (default location is ~/.kube/config).
4. Have a GitHub account.

Install Argo CD CLI

Once you have your cluster set and `kubectl` installed, let's install the Argo CD CLI tool. We will install it with `brew` for Mac OS, you can find other installation directives on Argo CD documentation.

brew tap argoproj/tap brew install argoproj/tap/argocd

Install Argo CD to the cluster

We need to install Argo CD to our cluster to be able to deploy applications.

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

This will create a namespace within your cluster and Argo CD services and applications.

Access Argo CD API Server

By default, Argo CD API server is not exposed to external IP for security reasons. For this tutorial, we will access the server using port forwarding. Kubectl port-forwarding is used to connect to the API server without exposing the service to outside. We will use the same method for our example application.

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

This will expose Argo CD service to localhost:8080.

Login to Argo CD in console

Before we access the Argo CD UI, we need to get and change the admin password. Let's list all the pods of `argocd` namespace.

kubectl get pods -n argocd | grep argocd-server

This will output Argo CD server pod details. The name of the pod is our first password for the admin user. Once you request to login, it will ask for a username and password. Use `admin` for username, the pod's name for the password.

argocd login localhost:8080

Change Argo CD Admin User Password

Once you logged in, change the password for the admin user with the following command. You will be asked to enter the old password and new password.

argocd account update-password

Login Argo CD UI

Now, let's go to localhost:8080 to access the UI.

Create a Github Repository

As we mentioned in the introduction, Argo CD follows GitOps flow. We will need a repository where we can store our application manifest files. Let's create a repository and put the following `deployment`, `service` and `argocd` application`YAML files into it. For this tutorial, I used https://github.com/omegion/echo-k8s-app.

Deployment

Create a `deployment.yaml` file with the following content.

apiVersion: apps/v1 kind: Deployment metadata: name: echo-deploymentspec: replicas: 1 selector: matchLabels: app: echo-server template: metadata: labels: app: echo-server spec: containers: - name: echo-server image: jmalloc/echo-server ports: - name: http-port containerPort: 8080

Service

Create a `service.yaml` file with the following content.

apiVersion: v1 kind: Service metadata: name: echo-server-servicespec: ports: - name: app port: 80 targetPort: 8080 selector: app: echo-server

Argo CD Application

Create an `argocd-app.yaml` file with the following content.

apiVersion: argoproj.io/v1alpha1 kind: Application metadata: name: echo-server # name of the Argo CD application namespace: argocdspec: project: default source: repoURL: https://github.com/omegion/echo-k8s-app/ # change here with your repository url targetRevision: HEAD path: kubernetes directory: recurse: true destination: server: https://kubernetes.default.svc namespace: echo-server # namespace we created syncPolicy: automated: prune: false selfHeal: false

After creating these files, push them to the repository. You can change `repoURL` with the created repository. I used an example repository for this tutorial.

Deploy Argo CD Application

Once we have all three files, let's apply the Argo CD Application YAML file with `kubectl`.

kubectl apply -f argocd-app.yaml

This will create an application in Argo CD UI.

Access Argo CD Application with Port Forward

In order to access an application from outside in the cluster, we would need an ingress. However, we didn't create ingress to access our application from outside in this tutorial. To access our example application, we need to use port-forwarding as we did for `argocd-server`.

kubectl port-forward svc/echo-server-service -n echo-server 8001:80

This will create a tunnel between your local port and the application. Visit
on your browser. You will see the request details.

Request served by echo-deployment-788c68557d-72fgl HTTP/1.1 GET / Host: localhost:8001 Accept-Language: en-GB,en-US;q=0.9,en;q=0.8,tr;q=0.7 Cache-Control: max-age=0 Upgrade-Insecure-Requests: 1 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36 Sec-Fetch-User: ?1 Sec-Fetch-Dest: document Connection: keep-alive Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9 Sec-Fetch-Site: none Sec-Fetch-Mode: navigate Accept-Encoding: gzip, deflate, br

Conclusion

In this tutorial, we installed Argo CD into our existing cluster and created a simple application. Since Argo CD follows GitOps flow, we needed to create a repository that Argo CD application can read the manifest files from. Finally, we connect to our application with port-forward through application service and test the echo server application.