31 ‐ ArgoCD - CloudScope/DevOpsWithCloudScope GitHub Wiki

1. Overview of ArgoCD

ArgoCD is a declarative, GitOps-based continuous delivery (CD) tool for Kubernetes. It is part of the Argo Project, which includes a suite of tools for running and managing Kubernetes workloads. ArgoCD focuses on automating the deployment and synchronization of applications in Kubernetes clusters by tracking and applying the desired state defined in a Git repository.

2. Key Features of ArgoCD

a. GitOps Workflow:

  • ArgoCD treats Git as the single source of truth for Kubernetes manifests, Helm charts, or Kustomize configurations.
  • It continuously monitors Git repositories for changes and syncs them with the live state of your Kubernetes cluster.

b. Declarative Deployment:

  • Applications are managed declaratively, meaning their configuration is defined in YAML or Helm and stored in Git.

c. Multi-Cluster Management:

  • ArgoCD supports deploying and managing applications across multiple Kubernetes clusters from a single instance.

d. Automated Syncing:

  • ArgoCD can automatically synchronize the live state of a cluster with the desired state from Git (auto-sync) or allow manual syncs.

e. Health and Drift Detection:

  • ArgoCD monitors application health and detects "drift" (when the live state deviates from the desired state).

f. Application Rollbacks:

  • Provides the ability to easily roll back to previous versions of your applications using Git history.

g. Rich UI and CLI:

  • ArgoCD offers a user-friendly web UI and a powerful CLI for managing and monitoring applications.

h. Integration with Tools:

  • ArgoCD integrates with Helm, Kustomize, Jsonnet, and plain YAML.
  • Supports notifications via Slack, Microsoft Teams, and other tools.

3. How ArgoCD Works

a. Git Repository as Source of Truth:

  • Your application configurations (YAML, Helm charts, or Kustomize files) are stored in a Git repository.

b. Application Management:

  • You define an "application" in ArgoCD, which links the desired state (Git repository and branch) to the live state (Kubernetes namespace).

c. Reconciliation:

  • ArgoCD continuously reconciles the desired state with the live state of your Kubernetes cluster.
  • If drift is detected, ArgoCD can alert you or automatically apply the changes.

d. Deployment Strategies:

  • ArgoCD supports progressive delivery strategies like blue-green and canary deployments when integrated with other tools like Argo Rollouts.

4. Why Use ArgoCD?

  • Declarative Deployment: Enables GitOps workflows, improving visibility and version control for Kubernetes applications.
  • Automation: Reduces manual intervention for deploying applications and synchronizing configurations.
  • Consistency: Ensures all clusters are always in sync with the desired state defined in Git.
  • Multi-Cluster Management: Centralizes control of multiple Kubernetes clusters.
  • Self-Healing: Detects and resolves drift automatically when configured.

5. ArgoCD Architecture

a. API Server:

  • Provides REST API and GraphQL endpoints.
  • Serves the Web UI.

b. Application Controller:

  • Watches Git repositories and Kubernetes clusters.
  • Ensures applications are reconciled to their desired state.

c. Repo Server:

  • Clones Git repositories and retrieves manifests for the Application Controller.

d. Redis:

  • Used for caching purposes to improve performance.

e. Dex (Optional):

  • An identity provider for single sign-on (SSO) with external authentication services (e.g., LDAP, GitHub, SAML).

6. When to Use ArgoCD

ArgoCD is ideal if:

  • You are managing Kubernetes applications and want to adopt GitOps principles.
  • You need a centralized way to manage applications across multiple clusters.
  • You want an automated, version-controlled, and auditable deployment process.
  • You need a self-healing mechanism for Kubernetes applications.

7. Key Components of ArgoCD

ArgoCD consists of the following core components:

a. Application Controller

  • Purpose:
    • Responsible for reconciling the desired state (defined in Git) with the live state (in Kubernetes).
    • Performs actions like sync, rollback, and auto-healing of applications.
  • Deployment: Runs as a Kubernetes controller.
  • Troubleshooting:
    • Check logs: 
      kubectl logs -n argocd deployment/argocd-application-controller
    • Ensure sufficient resources (CPU/Memory) are allocated to avoid delays in reconciliation.

b. Repo Server

  • Purpose:
    • Clones Git repositories and provides resource manifests to the Application Controller.
    • Handles Git operations and Helm chart rendering.
  • Deployment: Runs as a sidecar service in ArgoCD.
  • Troubleshooting:
    • Check logs for Git-related issues: 
      kubectl logs -n argocd deployment/argocd-repo-server
    • Common issues: SSH key misconfiguration, repository access permissions.

c. API Server

  • Purpose:
    • Provides the ArgoCD REST API and serves the Web UI.
    • Handles user authentication and authorization.
  • Deployment: Runs as a Kubernetes service and is accessible externally (if configured).
  • Troubleshooting:
    • Check logs for authentication/authorization issues: 
      kubectl logs -n argocd deployment/argocd-server
    • Ensure the Ingress/LoadBalancer service is properly configured for external access.

d. Redis

  • Purpose:
    • Acts as a caching layer for performance optimization.
  • Deployment: Runs as a Kubernetes service within the ArgoCD namespace.
  • Troubleshooting:
    • Monitor resource utilization to avoid bottlenecks.
    • Check pod logs for Redis errors: 
      kubectl logs -n argocd statefulset/argocd-redis

e. Dex (Optional)

  • Purpose:
    • Provides single sign-on (SSO) capabilities, integrating with external identity providers like LDAP, GitHub, or SAML.
  • Deployment: Only deployed if SSO is configured.
  • Troubleshooting:
    • Validate Dex configuration (argocd-cm ConfigMap).
    • Check logs for authentication errors: 
      kubectl logs -n argocd deployment/argocd-dex-server

8. Workflow of ArgoCD

a. GitOps Sync:

  • Monitors the Git repository for changes.
  • Fetches Kubernetes manifests or Helm charts.
  • Syncs the live cluster state with the desired state.

b. Health Monitoring:

  • Periodically checks the health of applications.
  • Supports custom health checks via Lua scripts.

c. Self-Healing:

  • Detects drift between the desired and live states.
  • Auto-sync can be configured to apply fixes automatically.

9. Common Configuration Files

  • argocd-cm (ConfigMap):

    • Stores core ArgoCD configurations like repositories, RBAC policies, and application settings.

  • argocd-rbac-cm (ConfigMap):

    • Defines role-based access control (RBAC) policies.

  • Secrets:

    • Stores sensitive information like Git credentials, SSH keys, and webhooks.

10. Key Features for DevOps

  • GitOps Workflow:

    • Allows a single source of truth (Git) for cluster configurations.
    • Promotes version control, review processes, and traceability.

  • Multi-Cluster Support:

    • Deploy applications to multiple clusters from a single ArgoCD instance.

  • Declarative Application Management:

    • Applications can be defined and managed declaratively using YAML.

  • Sync Options:

    • Manual or automated sync modes.
    • Prune (clean up unused resources) and dry-run modes.

  • Notifications:

    • Integrates with tools like Slack, Microsoft Teams, or email for deployment notifications.

11. Tips for Managing ArgoCD

  • Security:

    • Secure access to ArgoCD using RBAC.
    • Use secrets to manage sensitive data and credentials.

  • Monitoring:

    • Integrate with Prometheus and Grafana for monitoring application health and sync status.

  • Backup and Restore:

    • Backup ArgoCD configurations and secrets using tools like kubectl or Velero.

  • Resource Optimization:

    • Allocate sufficient resources for components like argocd-application-controller to handle large numbers of applications.

  • Namespace Isolation:

    • Use Project resources in ArgoCD to group applications and manage access for different teams.

12. Common Issues and Solutions

Issue Solution
Sync stuck at OutOfSync Check Git credentials, permissions, and repository URL.
Application fails during deployment Review ArgoCD application logs and container logs for detailed errors.
Unable to access ArgoCD UI Verify Ingress or LoadBalancer configuration. Ensure the argocd-server service is reachable.
Drift not being detected Ensure the auto-sync feature is enabled.
Authentication issues with SSO (Dex) Validate the Dex configuration and integration with the identity provider.

13. Useful Commands

  • List Applications:

    argocd app list

  • Sync an Application:

    argocd app sync <app-name>

  • Check Application Status:

    argocd app get <app-name>

  • Login to CLI:

    argocd login <argocd-server>

  • Delete an Application:

    argocd app delete <app-name>

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