ArgoCD GitOps

Implement declarative continuous delivery for Kubernetes with ArgoCD.

When to Use This Skill

Use this skill when:

• Implementing GitOps workflows for Kubernetes
• Automating deployments from Git repositories
• Managing multiple environments declaratively
• Implementing progressive delivery strategies
• Synchronizing cluster state with Git

Prerequisites

• Kubernetes cluster with ArgoCD installed
• kubectl configured
• Git repository for manifests
• ArgoCD CLI (optional)

Installation

# Create namespace
kubectl create namespace argocd

# Install ArgoCD
kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/install.yaml

# Get admin password
kubectl -n argocd get secret argocd-initial-admin-secret \
  -o jsonpath="{.data.password}" | base64 -d

# Port forward to access UI
kubectl port-forward svc/argocd-server -n argocd 8080:443

# Login with CLI
argocd login localhost:8080

Application Definition

Basic Application

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/org/myapp-manifests.git
    targetRevision: main
    path: environments/production
  destination:
    server: https://kubernetes.default.svc
    namespace: myapp
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    syncOptions:
      - CreateNamespace=true

Helm Application

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-helm
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/org/myapp-chart.git
    targetRevision: main
    path: charts/myapp
    helm:
      valueFiles:
        - values.yaml
        - values-production.yaml
      parameters:
        - name: replicaCount
          value: "3"
        - name: image.tag
          value: "2.0.0"
  destination:
    server: https://kubernetes.default.svc
    namespace: myapp
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

Kustomize Application

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-kustomize
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/org/myapp-manifests.git
    targetRevision: main
    path: overlays/production
    kustomize:
      images:
        - myapp=myregistry/myapp:2.0.0
  destination:
    server: https://kubernetes.default.svc
    namespace: myapp

Projects

apiVersion: argoproj.io/v1alpha1
kind: AppProject
metadata:
  name: myproject
  namespace: argocd
spec:
  description: My Project
  sourceRepos:
    - https://github.com/org/*
  destinations:
    - namespace: myapp-*
      server: https://kubernetes.default.svc
  clusterResourceWhitelist:
    - group: ''
      kind: Namespace
  namespaceResourceWhitelist:
    - group: '*'
      kind: '*'
  roles:
    - name: developer
      description: Developer role
      policies:
        - p, proj:myproject:developer, applications, get, myproject/*, allow
        - p, proj:myproject:developer, applications, sync, myproject/*, allow
      groups:
        - developers

Application Sets

Git Generator

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp-environments
  namespace: argocd
spec:
  generators:
    - git:
        repoURL: https://github.com/org/myapp-manifests.git
        revision: main
        directories:
          - path: environments/*
  template:
    metadata:
      name: 'myapp-{{path.basename}}'
    spec:
      project: default
      source:
        repoURL: https://github.com/org/myapp-manifests.git
        targetRevision: main
        path: '{{path}}'
      destination:
        server: https://kubernetes.default.svc
        namespace: 'myapp-{{path.basename}}'
      syncPolicy:
        automated:
          prune: true
          selfHeal: true

List Generator

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp-clusters
  namespace: argocd
spec:
  generators:
    - list:
        elements:
          - cluster: production
            url: https://prod-cluster.example.com
          - cluster: staging
            url: https://staging-cluster.example.com
  template:
    metadata:
      name: 'myapp-{{cluster}}'
    spec:
      project: default
      source:
        repoURL: https://github.com/org/myapp-manifests.git
        targetRevision: main
        path: 'environments/{{cluster}}'
      destination:
        server: '{{url}}'
        namespace: myapp

Matrix Generator

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp-matrix
  namespace: argocd
spec:
  generators:
    - matrix:
        generators:
          - git:
              repoURL: https://github.com/org/myapp-manifests.git
              revision: main
              directories:
                - path: apps/*
          - list:
              elements:
                - env: staging
                - env: production
  template:
    metadata:
      name: '{{path.basename}}-{{env}}'
    spec:
      project: default
      source:
        repoURL: https://github.com/org/myapp-manifests.git
        targetRevision: main
        path: '{{path}}/overlays/{{env}}'
      destination:
        server: https://kubernetes.default.svc
        namespace: '{{path.basename}}-{{env}}'

Sync Policies

Automated Sync

syncPolicy:
  automated:
    prune: true          # Delete resources not in Git
    selfHeal: true       # Revert manual changes
    allowEmpty: false    # Don't sync empty directories
  syncOptions:
    - CreateNamespace=true
    - PrunePropagationPolicy=foreground
    - PruneLast=true
  retry:
    limit: 5
    backoff:
      duration: 5s
      factor: 2
      maxDuration: 3m

Sync Waves

# In Kubernetes manifests
apiVersion: v1
kind: ConfigMap
metadata:
  name: myconfig
  annotations:
    argocd.argoproj.io/sync-wave: "-1"  # Sync first
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  annotations:
    argocd.argoproj.io/sync-wave: "0"   # Sync second

Sync Hooks

apiVersion: batch/v1
kind: Job
metadata:
  name: migration
  annotations:
    argocd.argoproj.io/hook: PreSync
    argocd.argoproj.io/hook-delete-policy: HookSucceeded
spec:
  template:
    spec:
      containers:
        - name: migrate
          image: myapp:latest
          command: ["./migrate.sh"]
      restartPolicy: Never

CLI Commands

# List applications
argocd app list

# Get application details
argocd app get myapp

# Sync application
argocd app sync myapp

# Force sync (ignore differences)
argocd app sync myapp --force

# View diff
argocd app diff myapp

# Rollback
argocd app rollback myapp

# Delete application
argocd app delete myapp

# View logs
argocd app logs myapp

# Hard refresh (clear cache)
argocd app get myapp --hard-refresh

Repository Configuration

apiVersion: v1
kind: Secret
metadata:
  name: private-repo
  namespace: argocd
  labels:
    argocd.argoproj.io/secret-type: repository
stringData:
  url: https://github.com/org/private-repo.git
  username: git
  password: ghp_xxxx
---
# SSH key
apiVersion: v1
kind: Secret
metadata:
  name: private-repo-ssh
  namespace: argocd
  labels:
    argocd.argoproj.io/secret-type: repository
stringData:
  url: [email protected]:org/private-repo.git
  sshPrivateKey: |
    -----BEGIN OPENSSH PRIVATE KEY-----
    ...
    -----END OPENSSH PRIVATE KEY-----

Notifications

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-notifications-cm
  namespace: argocd
data:
  service.slack: |
    token: $slack-token
  template.app-deployed: |
    message: Application {{.app.metadata.name}} is now {{.app.status.sync.status}}.
  trigger.on-deployed: |
    - when: app.status.operationState.phase in ['Succeeded']
      send: [app-deployed]

Common Issues

Issue: Sync Fails with Diff

Problem: Resources show differences but are correct Solution: Configure ignore differences

spec:
  ignoreDifferences:
    - group: apps
      kind: Deployment
      jsonPointers:
        - /spec/replicas

Issue: Repository Not Accessible

Problem: ArgoCD cannot clone repository Solution: Check repository secret, verify URL and credentials

Issue: Application Stuck OutOfSync

Problem: Application never becomes synced Solution: Check resource status, review events, verify manifests

Issue: Health Check Failing

Problem: Application shows degraded health Solution: Check custom health checks, verify probe configurations

Best Practices

• Use ApplicationSets for multi-environment deployments
• Implement sync waves for ordered deployments
• Use projects to isolate applications
• Configure notifications for deployment events
• Implement proper RBAC with projects
• Use health checks for deployment verification
• Enable auto-pruning to remove deleted resources
• Keep manifests in dedicated repositories

Related Skills

• kubernetes-ops - K8s fundamentals
• helm-charts - Helm deployments
• kustomize - Kustomize overlays