Getting Started with Argo CD: A Beginner’s Guide

Understanding the Components, Features and Install

The article series consists of the following headings.

• 1- Understanding the Components, Features and Install
• 2- Public repository example
• 3- Private repository example
• 4- App-of-apps behaivours
• 5- Image Updater Install and Example

Introduction

Argo CD is a GitOps Continuous delivery tool for Kubernetes environments. Argo CD has an architecture that references the “Single Source of Truth” model, which is the basic building block of GitOps.

ArgoCD advantages:

• Faster deployments
• Safer distributions
• Faster rollback
• Simple control
• Better traceability
• Eliminate configuration drift

ArgoCD Architecture Diagram

Key features of Argo CD

• GitOps Approach: Argo CD is based on GitOps principles. According to these principles, application state and configuration are stored in a Git repository. This allows application state and configuration to be managed and tracked like code.
• Continuous Deployment: Argo CD enables continuous deployment of applications running on Kubernetes. New versions, changes, or configuration updates can be automatically applied based on changes in the Git repository.
• Change Tracking and Rollback: Argo CD tracks changes made and updates the application state based on those changes. It also offers the ability to undo changes made.
• Declarative Application Definition: Application state and configuration are defined through YAML-based declarative files. These files specify application, service and other resources.
• Multimedia Support: Argo CD supports application deployment across different environments (e.g. dev, test, prod). A separate configuration can be defined for each environment.
• Customizable Application Status Control: Argo CD provides sample flexibility to customize the application health checking process and add custom checkpoints as needed.
• Web Based User Interface: Argo CD provides an easy-to-use web-based interface for users. This interface offers application status, history changes, and the ability to switch between applications.
• Open Source and Wide Ecosystem Support: Argo CD is an open source project and works in harmony with the Kubernetes ecosystem. It also comes with a wide ecosystem that offers a number of plugins and integrations.

ArgoCD Install

You can install argocd with the following command.

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

# v2.11.3
kubectl create namespace argocd
kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/v2.11.3/manifests/install.yaml

# checking all object
kubectl get all -n argocd 

After installing, you can use the command below to get the password for argocd ui login. But first, we need to open the service to the outside as nodeport.

# patch to nodePort
kubectl patch svc argocd-server -n argocd -p '{"spec": {"type": "NodePort"}}'

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

• ArgoCD-UI: kubernetes_master_node_ip : NodePort_Ip
• Username: admin
• Password: is the string value resulting from the above command.

Application.yaml Description for ArgoCD

You can see the application.yaml manifest example below. To explain this .yaml keyword a little.

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: example-application
  namespace: argocd
labels:
    owner: deniz turkmen
spec:
  destination:
    server: https://kubernetes.default.svc
    namespace: default
  project: default
  source:
    repoURL: <repository_url>
    targetRevision: <branch_or_commit>
    path: <path_to_yaml_files>
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

Now, let’s break down the YAML file in detail:

• apiVersion: Specifies the API version of the ArgoCD resource.
• kind: Specifies the kind of resource, which in this case is an application.
• metadata: Contains metadata about the application.
• name: Specifies the name of the application.
• namespace: Specifies the namespace in which the application resides. Here, it's in the argocd namespace.
• labels: Contains labels to help identify and manage the application.
• spec: Contains the specification of the application.
• project: Specifies the ArgoCD project the application belongs to. In this case, it's the default project.
• destination: Specifies where the application should be deployed.
• server: Specifies the Kubernetes API server URL.
• namespace: Specifies the namespace where the application should be deployed.
• source: Specifies the source of the application manifest files.
• repoURL: Specifies the URL of the Git repository containing the application manifests.
• targetRevision: Specifies the Git branch, tag, or commit SHA to sync the application to. Here, it's set to the main branch.
• path: Specifies the directory within the repository containing the application manifests. In this case, it's manifests.
• syncPolicy: Specifies the synchronization policy for the application.
• automated: Specifies that synchronization should be automated.
• prune: Specifies whether resources that are no longer defined in the Git repository should be pruned.
• selfHeal: Specifies whether ArgoCD should attempt to reconcile the live state of the application with the desired state defined in the Git repository.

Application Healty Status;

Argo CD tracks synced/out-of-sync status as well as service status for each deployed application. Health status is shown in the user interface.

• Healthy: The source is 100% healthy.
• Progressing: The source is not healthy but it can be healthy.
• Suspended: The source is suspended and stopped. Cronjob example of typically.
• Missing: There is no resources in the cluster.
• Degraded: Resource status indicates failure or the resource did not reach a healthy state in time.
• Unknown: Health assessment failed and true health status is unknown.

Conclusion

As a result, argocd is a very powerful continuous delivery tool. It has fast deployment, rollback, powerful features and components. Additionally, the UI is useful for management.