Module 3: Deploying the Todo App with GitOps

Module Overview

This module focuses on deploying a Todo application using GitOps principles. Participants will learn how to set up a GitOps repository, define the desired state of the application, and use Argo CD for deployment. Additionally, they will explore Gitea as an alternative Git service and perform hands-on tasks to deploy the Todo app using GitOps.

Key Learning Objectives

Understand the GitOps workflow for application deployment.
Learn how to set up and manage a GitOps repository.
Use Argo CD for real-time synchronization and health monitoring.
Explore Gitea as a self-hosted Git service and its integration with Argo CD.
Deploy a Todo app using GitOps principles and observe automated deployment processes.

Setting up the GitOps Repository

Initializing the Git Repository

Below is an example of creating a repo to be used for GitOps. Follow these steps:

Create a new repository on your preferred Git hosting service (e.g., GitHub, GitLab).
Clone the repository to your local machine:

git clone <repository-url>
cd <repository-name>

Initialize the GitOps structure by creating the following directories:

mkdir -p manifests/base manifests/overlays/production

Add the necessary Kubernetes manifests (e.g., deployment.yaml, service.yaml) to the manifests/base directory.
Commit and push the changes to the repository:

git add .
git commit -m "Initialize GitOps repository"
git push origin main

GitOps-Compatible Structure

Ensure your repository follows a GitOps-compatible structure. This typically includes:

A base directory for common configurations.
An overlays directory for environment-specific configurations (e.g., production, staging).
Kubernetes manifests (YAML files) defining the desired state of the application.

Defining the Desired State

Key Resources

The desired state of the Todo application in Git. Key resources include:

Deployment: Specifies the desired state of the application pods.
Service: Exposes the application to the network.
ConfigMap/Secret: Stores configuration data and sensitive information.
Route: to be used for comminucation into the application.

Version Control and Traceability

Use Git branches for different environments (e.g., main for production, develop for staging).
Tag releases for traceability and rollback capabilities.
Maintain detailed commit messages to track changes.

Using Argo CD for Deployment

Synchronizing with Argo CD

When using Argo CD to synchronize the application deployment on OpenShift with the Git repository:

Install Argo CD on your OpenShift cluster.
Create an Argo CD application pointing to your Git repository:

argocd app create todo-app \
   --repo <repository-url> \
   --path manifests/overlays/production \
   --dest-server https://kubernetes.default.svc \
   --dest-namespace default

Sync the application to deploy it:

argocd app sync todo-app

Real-Time Synchronization and Health Monitoring

ArgoCD has features such as:

Real-Time Synchronization: Automatically updates the deployment when changes are pushed to the Git repository.
Health Monitoring: Monitors the health of the application and reports any issues.

Integration with Argo CD

Repository Authentication: Use Gitea tokens for authentication.
Webhooks: Configure webhooks in Gitea to trigger Argo CD synchronization.

Hands-On Task

Deploying the Todo App

Navigate to the Gitea Project

Access the Gita URL

Change the app-config/cluster-config.yaml to your repo url

Example https://gitea-gitea.apps.ocp4.example.com/yourusername/todo-demo-app-helmrepo.git

Change the app/kustomization.yaml namespace to your namespace

namespace todo-demo-app-yourusername

spec→destination→namespace todo-demo-app-yourusername

spec→project yourusername-project

Login into the ArgoCD instance

Located under openshift-gitops → Routes Menu Click on openshift-gitops-server Location

Click on LOG IN VIA OPENSHIFT

Use your OpenShift username and password to access cluster and Authorize Access

Configure your Repo under Settings→Repositories

Enter the vaules below

Type git
Project yourusername-project
Repository URL https://gitea-gitea.apps.ocp4.example.com/yourusername/todo-demo-app-helmrepo.git
Username (optional) user1
Password (optional)

Validate the connection was Successful

Copy the configuration from your Gitea Repo into ArgoCD

Click on the EDIT AS YAML

Save the yaml configuration in ArgoCD

Click Create to start deployment

Validate ArgoCD Sync status

Navigate to your todo-demo-app-yourusername namespace and select route

View deployed application

Module Summary

Key takeaways from this module include:

Understanding the GitOps workflow for application deployment.
Setting up and managing a GitOps repository.
Using Argo CD for real-time synchronization and health monitoring.
Exploring Gitea as a self-hosted Git service and its integration with Argo CD.
Deploying a Todo app using GitOps principles and observing automated deployment processes.