What is Argo CD? Declarative GitOps CD for Kubernetes

What is Argo CD? Declarative GitOps CD for Kubernetes

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3 min read

Introduction

Argo CD is a Kubernetes controller, responsible for continuously monitoring all running applications and comparing their live state to the desired state specified in the Git repository.

What is Argo CD used for?

ArgoCD is an easy to use tool that allows development teams to deploy and manage applications without having to learn a lot about Kubernetes, and without needing full access to the Kubernetes system.

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.

Getting Started

kubectl create namespace argocd

kubectl apply -n argocd -f raw.githubusercontent.com/argoproj/argo-cd/..

Follow the ArgoCD official guide getting started guide. Further user oriented documentation is provided for additional features. If you are looking to upgrade ArgoCD, see the upgrade guide. Developer oriented documentation is available for people interested in building third-party integrations.

How it 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:

  • kustomize applications

  • helm charts

  • jsonnet files

  • Plain directory of YAML/json manifests

  • 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 pinned to a specific version of manifests at a Git commit. See tracking strategies for additional details about the different tracking strategies available.

Architecture Overview

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Argo CD is implemented as a kubernetes controller which continuously monitors running applications and compares the current, live state against the desired target state (as specified in the Git repo). A deployed application whose live state deviates from the target state is considered OutOfSync. Argo CD reports & visualizes the differences, while providing facilities to automatically or manually sync the live state back to the desired target state. Any modifications made to the desired target state in the Git repo can be automatically applied and reflected in the specified target environments.

For additional details, see architecture overview.

Features

  • Automated deployment of applications to specified target environments

  • Support for multiple config management/templating tools (Kustomize, Helm, Jsonnet, plain-YAML)

  • Ability to manage and deploy to multiple clusters

  • SSO Integration (OIDC, OAuth2, LDAP, SAML 2.0, GitHub, GitLab, Microsoft, LinkedIn)

  • Multi-tenancy and RBAC policies for authorization

  • Rollback/Roll-anywhere to any application configuration committed in Git repository

  • Health status analysis of application resources

  • Automated configuration drift detection and visualization

  • Automated or manual syncing of applications to its desired state

  • Web UI which provides real-time view of application activity

  • CLI for automation and CI integration

  • Webhook integration (GitHub, BitBucket, GitLab)

  • Access tokens for automation

  • PreSync, Sync, PostSync hooks to support complex application rollouts (e.g.blue/green & canary upgrades)

  • Audit trails for application events and API calls

  • Prometheus metrics

  • Parameter overrides for overriding helm parameters in Git