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Architectural Overview

Argo CD Architecture


API Server

The API server is a gRPC/REST server which exposes the API consumed by the Web UI, CLI, and CI/CD systems. It has the following responsibilities:

  • application management and status reporting
  • invoking of application operations (e.g. sync, rollback, user-defined actions)
  • repository and cluster credential management (stored as K8s secrets)
  • authentication and auth delegation to external identity providers
  • RBAC enforcement
  • listener/forwarder for Git webhook events

Repository Server

The repository server is an internal service which maintains a local cache of the Git repository holding the application manifests. It is responsible for generating and returning the Kubernetes manifests when provided the following inputs:

  • repository URL
  • revision (commit, tag, branch)
  • application path
  • template specific settings: parameters, helm values.yaml

Application Controller

The application controller is a Kubernetes controller which continuously monitors running applications and compares the current, live state against the desired target state (as specified in the repo). It detects OutOfSync application state and optionally takes corrective action. It is responsible for invoking any user-defined hooks for lifecycle events (PreSync, Sync, PostSync)