Argocd-demo-app

What Is Argo CD?

Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes. It syncs Kubernetes manifests from a Git repository and ensures the live state of the cluster matches the desired state.

Why Argo CD?

Application definitions, configurations, and environments should be declarative and version controlled. Application deployment and lifecycle management should be automated, auditable, and easy to understand.

Benefits of Argo CD

1. whole k8s configuration defined in code git repo.

2. config files are not applied manually from from local laptops.

3. git remains a single source of truth i.e if some one changes in the cluster for the manifest files, argocd detects manual changes it will overwrite those with respect git configurations only.

4. Easy rollback by using git revert the previous verssions

5. cluster disaster recovery

Core Components of ArgoCD

1. argocd-server-*

✅ Provides the Web UI and REST API.

✅ Handles user interactions (login, trigger syncs, manage apps).

✅ Talks to Redis, the application controller, and repo server.

2. argocd-repo-server-*

✅ Clones and renders the Git repository content.

✅ Handles Helm, Kustomize, plain YAML, etc.

✅ Passes the rendered manifests to the application-controller.

3. argocd-application-controller-0

✅ The brains of ArgoCD.

✅ Continuously monitors applications defined as Application CRDs.

✅ Compares the live cluster state with the desired Git state.

✅ If out of sync, it handles synchronization (depending on policy: auto/manual).

4. argocd-applicationset-controller-*

✅ Manages ApplicationSet resources.

✅ Used to dynamically generate multiple Application objects based on a template.

Common use cases:

✅ Deploying to multiple clusters/environments

✅ Managing microservices from a monorepo

5. argocd-redis-*

🧠 What it does?

✅ Acts as in-memory cache to boost performance.

Used mainly by:

✅ argocd-server and argocd-repo-server

✅ Stores transient app state, repo cache, etc.

6. argocd-notifications-controller-*

✅ Handles notifications about ArgoCD application events:

✅ Sync success/failure

✅ Health status changes

Sends alerts to:

✅ Slack, Microsoft Teams, Webhooks, etc.

7. argocd-dex-server-*

✅ Dex is an OpenID Connect (OIDC) identity provider.

✅ Handles SSO authentication in ArgoCD (LDAP, GitHub, Google, etc.).

✅ Works with ArgoCD’s RBAC to restrict/allow access.

Note: As above all & points are pods, once you install the ArgoCD in the K8s you can able to see. Same has added the screenshot. https://github.com/viswa2/argocd-demo-app?tab=readme-ov-file#deploy-argocd-in-k8s-cluster

How They Work's Together?

How does ArgoCD works?

Argo CD follows the GitOps pattern of using Git repositories as the source of truth for defining the desired application state. Kubernetes manifests can be specified in several ways:

✅ ArgoCD continuously monitors a Git repo

✅ It compares the desired state (Git) with the live state (K8s)

✅ If they differ, it can automatically sync (or wait for manual sync)

✅ It Supports kustomize applications, helm charts, jsonnet files, Plain directory of YAML/json manifests and Any custom config management tool configured as a config management plugin

Argo CD automates the deployment of the desired application states in the specified target environments. Application deployments can track updates to branches, tags, or be pinned to a specific version of manifests at a Git commit

Architecture:

Reference Link: https://argo-cd.readthedocs.io/en/stable/

Prerequesites

1. Install kubernetes cluster in your local system i.e Minikube, Kind or EKS in AWS etc.

2. Installed Minikube in my local system which requires docker driver, so before installing minkube install docker in your respective systems or OS.

Reference Link for minikube install: https://minikube.sigs.k8s.io/docs/start/?arch=%2Fmacos%2Farm64%2Fstable%2Fbinary+download

3. After installing start the command called minikube start it will start the minikube cluster

4. check status minikube status

5. brew install argocd --> It will download the argocd cli and play around with it.

Link for ArgoCd Commands Refrence: https://argo-cd.readthedocs.io/en/stable/user-guide/commands/argocd/

Getting Started with Handson

1. Deploy argoCD in k8s cluster

2. Configure argocd with k8s manifest files

3. Test our setup by updating deployment.yaml files

Deploy ArgoCD in K8s Cluster

1. kubectl create ns argocd

2. kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/install.yaml —> Install all manifests for argocd requirements

3. kubectl port-forward svc/argocd-server 8080:443 -n argocd —> We need to login the argocd ui we are doing port forward

4. kubectl get pod, svc -n argocd --> check the pod svc status

5. https://localhost:8080/ —> login the ui, the default username is admin

6. kubectl -n argocd get secret argocd-initial-admin-secret -o jsonpath="{.data.password}" | base64 --decode && echo --> To get the passowrd to login the ArgoCD UI.

Reference Link to install necessary configurations: https://argo-cd.readthedocs.io/en/stable/getting_started/

Configure Argocd With K8s Manifest Files

1. Create a git repository —> Ex: Argo CD app config

2. Add or push the application manifest files along with the application.yaml file

3. Create application.yaml file and specify the source and destination paths, automate sync options, automatic self heal options etc.

4. Once ready push the configurations files into git repo.

5. For the first fime you need to apply manually kubectl apply -f application.yaml in the kubernetes cluster

6. Check the synced project in argocd UI.

Test Our Setup by Updating Deployment.yaml File

1. Automate Sync Test

To test with the automate sync in the git repo deployment.yaml file changed the image version from 0.2 to 0.1 and commit the change. as soon as change detected in the git repo argocd detects it. deployed newer version.

2. Pruning Test

If i want delete something in the configuration of yaml files or yaml file itself argocd detects it needs to remove automatically.

3. Manual Chnages in the kubernetes cluster

Tried to edit the deployment of guestbook with the no.of replicas 2 to 4, but argrocd undos manual changes, since we have enabled the automated self heal feature in deployment.yaml file

Note: ArgoCD polls git repository every 3 minutes, if you want to avoid that, as soon as chnages pushes into git repo it will syncronize we can acheive by using webhook configuration.

In the ArgoCD UI click on applications --> application name i.e guestbook-ui-argo-application and we can check the Events, logs, live manifest and desired manifests etc.

Working With Multiple Cluster Nodes

Configure and manage just 1 argocd, same argocd instance is able to sync fleet of k8s cluster.

Working With Multiple Cluster Environments

Each environment we need deploy argocd and test the application. We can test DEV environment first and move with the higher environments. i.e (DEV, TEST, PRE-PROD, PROD)