Argo CD: Up and Running

Chapter 4. Managing Applications

Argo CD manages the lifecycle of Kubernetes resources using a construct called Applications. An Argo CD Application is a custom resource that contains a logical collection of related Kubernetes resources (i.e., a collection of YAML or JSON files). An Argo CD Application is the smallest unit of work in Argo CD and is where Argo CD interfaces with Kubernetes in order to deploy Kubernetes objects.

Note

Application templating is possible with ApplicationSets, which will be discussed in Chapter 10.

In this chapter, we will cover the basics of an Argo CD Application, the different components (including an overview of the types of sources Applications can connect to), and how to use different Kubernetes templating tools that Argo CD natively supports. To wrap up this chapter, we’ll cover the lifecycle of an Argo CD Application.

Application Overview

As previously mentioned, an Argo CD Application is the atomic working unit in Argo CD. It defines the end state of the desired set of resources within a Kubernetes cluster, more specifically, it defines which objects need to be applied to the running Kubernetes cluster. Let’s take a look at an example of an Argo CD Application:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: guestbook
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/argoproj-labs/argocd-example-apps/
    targetRevision: main
    path: guestbook/
  destination:
    server: https://kubernetes.default.svc ...