What is ArgoCD, why GitOps, installation and first look

What is Argo CD?

Argo CD is a tool that lets you deploy applications on a Kubernetes cluster.

A Quick Kubernetes Refresher

Imagine you want to build a small app that converts Word documents to PDF, called wordtopdf.com. First you write the code. Once the code is ready, you need to deploy it so other people can access it. You buy a server and place your code inside it.

Your first customer, Bob, uses the app and doesn't mind occasional outages when the server is down. But if the website becomes popular with thousands of paying customers, they cannot tolerate those outages. Your first instinct might be to buy more servers so when one is down the others still function. That is the right intuition, but simply buying servers won't solve the issue without introducing a lot of complexity. Servers need to communicate with each other, and when one becomes unavailable, the workloads (the application within your server) need to migrate to another one.

Kubernetes lets you do all those things in a simple and efficient way.

The GitOps Approach

Suppose you have a Kubernetes cluster with three nodes (nodes are how servers are called in Kubernetes). How would you install an app and its components into this cluster? The safest and most modern approach is called the GitOps approach, and Argo CD is the most popular tool that follows it.

In the traditional approach, you would push the code of the application inside your Kubernetes cluster. With Argo CD and the GitOps approach, you install Argo CD within your cluster and point it to a Git repository. Once pointed, Argo CD continuously watches this repository. Every time there is a change, Argo CD uses it and installs the application back to your cluster. You never need to share credentials of your cluster externally. The only thing you need to do is let Argo CD access your Git repository.

The Argo CD User Interface

To see Argo CD in action, press the Start Argo CD button. In about a minute, you will get an Argo CD instance with all the details you need. Copy the credentials and press the Argo CD URL. Type your credentials in the login box.

This is the user interface of Argo CD. Application is the main entry point where you create your apps. You can press New App and explore the fields that are listed there.