argocd-expert

SKILL.md

ArgoCD Expert

You are an expert in ArgoCD with deep knowledge of GitOps workflows, application deployment, sync strategies, RBAC, and production operations. You design and manage declarative, automated deployment pipelines following GitOps best practices.

Core Expertise

ArgoCD Architecture

Components:

ArgoCD:
├── API Server (UI/CLI/API)
├── Repository Server (Git interaction)
├── Application Controller (K8s reconciliation)
├── Redis (caching)
├── Dex (SSO/RBAC)
└── ApplicationSet Controller (multi-cluster)

Installation

Install ArgoCD:

# Create namespace
kubectl create namespace argocd

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

# Install with HA
kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/ha/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 via CLI
argocd login localhost:8080 --username admin --password <password>

# Change admin password
argocd account update-password

Production Installation with Custom Values:

# argocd-values.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cm
  namespace: argocd
data:
  # Repository credentials
  repositories: |
    - url: https://github.com/myorg/myrepo
      passwordSecret:
        name: github-secret
        key: password
      usernameSecret:
        name: github-secret
        key: username

  # Resource customizations
  resource.customizations: |
    networking.k8s.io/Ingress:
      health.lua: |
        hs = {}
        hs.status = "Healthy"
        return hs

  # Timeout settings
  timeout.reconciliation: 180s

  # Diff customizations
  resource.compareoptions: |
    ignoreAggregatedRoles: true

  # UI customization
  ui.cssurl: "https://cdn.example.com/custom.css"

Application CRD

Basic Application:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp
  namespace: argocd
  finalizers:
  - resources-finalizer.argocd.argoproj.io
spec:
  project: production

  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: k8s/overlays/production

  destination:
    server: https://kubernetes.default.svc
    namespace: production

  syncPolicy:
    automated:
      prune: true
      selfHeal: true
      allowEmpty: false
    syncOptions:
    - CreateNamespace=true
    retry:
      limit: 5
      backoff:
        duration: 5s
        factor: 2
        maxDuration: 3m

Helm Application:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-helm
  namespace: argocd
spec:
  project: production

  source:
    repoURL: https://github.com/myorg/helm-charts
    targetRevision: main
    path: charts/myapp
    helm:
      releaseName: myapp
      valueFiles:
      - values.yaml
      - values-production.yaml
      parameters:
      - name: image.tag
        value: "v2.0.0"
      - name: replicaCount
        value: "5"
      values: |
        ingress:
          enabled: true
          hosts:
          - myapp.example.com

  destination:
    server: https://kubernetes.default.svc
    namespace: production

  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    syncOptions:
    - CreateNamespace=true

Kustomize Application:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-kustomize
  namespace: argocd
spec:
  project: production

  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: k8s/overlays/production
    kustomize:
      namePrefix: prod-
      nameSuffix: -v2
      images:
      - myregistry.io/myapp:v2.0.0
      commonLabels:
        environment: production
      commonAnnotations:
        managed-by: argocd

  destination:
    server: https://kubernetes.default.svc
    namespace: production

  syncPolicy:
    automated:
      prune: true
      selfHeal: true

AppProject

Project with RBAC:

apiVersion: argoproj.io/v1alpha1
kind: AppProject
metadata:
  name: production
  namespace: argocd
spec:
  description: Production applications

  # Source repositories
  sourceRepos:
  - https://github.com/myorg/*
  - https://charts.bitnami.com/bitnami

  # Destination clusters and namespaces
  destinations:
  - namespace: production
    server: https://kubernetes.default.svc
  - namespace: monitoring
    server: https://kubernetes.default.svc

  # Cluster resource whitelist
  clusterResourceWhitelist:
  - group: '*'
    kind: '*'

  # Namespace resource blacklist
  namespaceResourceBlacklist:
  - group: ''
    kind: ResourceQuota
  - group: ''
    kind: LimitRange

  # RBAC roles
  roles:
  - name: developer
    description: Developers can sync apps
    policies:
    - p, proj:production:developer, applications, sync, production/*, allow
    - p, proj:production:developer, applications, get, production/*, allow
    groups:
    - developers

  - name: admin
    description: Admins have full access
    policies:
    - p, proj:production:admin, applications, *, production/*, allow
    groups:
    - platform-team

  # Sync windows
  syncWindows:
  - kind: allow
    schedule: '0 9 * * 1-5'  # 9 AM weekdays
    duration: 8h
    applications:
    - '*'
  - kind: deny
    schedule: '0 0 * * 0,6'  # Weekends
    duration: 24h
    applications:
    - '*'

  # Orphaned resources
  orphanedResources:
    warn: true

ApplicationSet

Git Generator (Multi-Environment):

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp-environments
  namespace: argocd
spec:
  generators:
  - git:
      repoURL: https://github.com/myorg/myapp
      revision: main
      directories:
      - path: k8s/overlays/*

  template:
    metadata:
      name: 'myapp-{{path.basename}}'
    spec:
      project: production
      source:
        repoURL: https://github.com/myorg/myapp
        targetRevision: main
        path: '{{path}}'
      destination:
        server: https://kubernetes.default.svc
        namespace: '{{path.basename}}'
      syncPolicy:
        automated:
          prune: true
          selfHeal: true

List Generator (Multi-Cluster):

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp-clusters
  namespace: argocd
spec:
  generators:
  - list:
      elements:
      - cluster: us-east-1
        url: https://cluster1.example.com
        namespace: production
      - cluster: us-west-2
        url: https://cluster2.example.com
        namespace: production
      - cluster: eu-central-1
        url: https://cluster3.example.com
        namespace: production

  template:
    metadata:
      name: 'myapp-{{cluster}}'
    spec:
      project: production
      source:
        repoURL: https://github.com/myorg/myapp
        targetRevision: main
        path: k8s/overlays/production
      destination:
        server: '{{url}}'
        namespace: '{{namespace}}'
      syncPolicy:
        automated:
          prune: true
          selfHeal: true

Matrix Generator (Environments × Clusters):

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp-matrix
  namespace: argocd
spec:
  generators:
  - matrix:
      generators:
      - git:
          repoURL: https://github.com/myorg/myapp
          revision: main
          directories:
          - path: k8s/overlays/*
      - list:
          elements:
          - cluster: prod-us
            url: https://prod-us.example.com
          - cluster: prod-eu
            url: https://prod-eu.example.com

  template:
    metadata:
      name: 'myapp-{{path.basename}}-{{cluster}}'
    spec:
      project: production
      source:
        repoURL: https://github.com/myorg/myapp
        targetRevision: main
        path: '{{path}}'
      destination:
        server: '{{url}}'
        namespace: '{{path.basename}}'
      syncPolicy:
        automated:
          prune: true
          selfHeal: true

Sync Strategies

Automatic Sync with Policies:

syncPolicy:
  automated:
    prune: true        # Delete resources not in Git
    selfHeal: true     # Force sync on drift
    allowEmpty: false  # Prevent deletion of all resources

  syncOptions:
  - CreateNamespace=true
  - PrunePropagationPolicy=foreground
  - PruneLast=true
  - ApplyOutOfSyncOnly=true
  - RespectIgnoreDifferences=true
  - ServerSideApply=true

  retry:
    limit: 5
    backoff:
      duration: 5s
      factor: 2
      maxDuration: 3m

Sync Hooks:

apiVersion: batch/v1
kind: Job
metadata:
  name: database-migration
  annotations:
    argocd.argoproj.io/hook: PreSync
    argocd.argoproj.io/hook-delete-policy: HookSucceeded
    argocd.argoproj.io/sync-wave: "1"
spec:
  template:
    spec:
      containers:
      - name: migration
        image: myapp:latest
        command: ["./migrate.sh"]
      restartPolicy: Never
---
apiVersion: batch/v1
kind: Job
metadata:
  name: smoke-test
  annotations:
    argocd.argoproj.io/hook: PostSync
    argocd.argoproj.io/hook-delete-policy: BeforeHookCreation
    argocd.argoproj.io/sync-wave: "5"
spec:
  template:
    spec:
      containers:
      - name: test
        image: curlimages/curl:latest
        command: ["curl", "http://myapp/health"]
      restartPolicy: Never

SSO Configuration

Dex with GitHub:

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cm
  namespace: argocd
data:
  url: https://argocd.example.com
  dex.config: |
    connectors:
    - type: github
      id: github
      name: GitHub
      config:
        clientID: $dex.github.clientId
        clientSecret: $dex.github.clientSecret
        orgs:
        - name: myorg
          teams:
          - platform-team
          - developers
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-rbac-cm
  namespace: argocd
data:
  policy.default: role:readonly
  policy.csv: |
    # Admins have full access
    g, myorg:platform-team, role:admin

    # Developers can sync apps
    g, myorg:developers, role:developer

    # Developer role definition
    p, role:developer, applications, get, */*, allow
    p, role:developer, applications, sync, */*, allow
    p, role:developer, repositories, get, *, allow
    p, role:developer, projects, get, *, allow

  scopes: '[groups, email]'

Health Checks

Custom Health Check:

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cm
  namespace: argocd
data:
  resource.customizations.health.argoproj.io_Rollout: |
    hs = {}
    if obj.status ~= nil then
      if obj.status.conditions ~= nil then
        for i, condition in ipairs(obj.status.conditions) do
          if condition.type == "Progressing" and condition.reason == "RolloutCompleted" then
            hs.status = "Healthy"
            hs.message = "Rollout completed"
            return hs
          end
        end
      end
    end
    hs.status = "Progressing"
    hs.message = "Rollout in progress"
    return hs

argocd CLI Commands

Application Management:

# Create application
argocd app create myapp \
  --repo https://github.com/myorg/myapp \
  --path k8s/overlays/production \
  --dest-server https://kubernetes.default.svc \
  --dest-namespace production

# List applications
argocd app list
argocd app list -o wide

# Get application details
argocd app get myapp
argocd app get myapp --refresh

# Sync application
argocd app sync myapp
argocd app sync myapp --prune
argocd app sync myapp --dry-run
argocd app sync myapp --force

# Rollback
argocd app rollback myapp

# Delete application
argocd app delete myapp
argocd app delete myapp --cascade=false  # Keep resources

Repository Management:

# Add repository
argocd repo add https://github.com/myorg/myapp \
  --username myuser \
  --password mytoken

# List repositories
argocd repo list

# Remove repository
argocd repo rm https://github.com/myorg/myapp

Cluster Management:

# Add cluster
argocd cluster add my-cluster-context

# List clusters
argocd cluster list

# Remove cluster
argocd cluster rm https://cluster.example.com

Project Management:

# Create project
argocd proj create production

# Add repository to project
argocd proj add-source production https://github.com/myorg/*

# Add destination to project
argocd proj add-destination production \
  https://kubernetes.default.svc \
  production

# List projects
argocd proj list

# Get project details
argocd proj get production

Best Practices

1. Use AppProjects

# Separate projects by team/environment
- production
- staging
- development

2. Enable Auto-Sync with Pruning

syncPolicy:
  automated:
    prune: true
    selfHeal: true

3. Use Sync Waves

annotations:
  argocd.argoproj.io/sync-wave: "1"  # Deploy order

4. Implement Health Checks

# Custom health checks for CRDs
resource.customizations.health.<group>_<kind>

5. Use Sync Windows

# Control deployment times
syncWindows:
- kind: allow
  schedule: '0 9 * * 1-5'  # Business hours
  duration: 8h

6. Enable Notifications

# Slack, Teams, email notifications
argocd admin notifications controller

7. Use ApplicationSets

# Manage multiple apps declaratively
kind: ApplicationSet

Anti-Patterns

1. No Resource Pruning:

# BAD: Orphaned resources
automated: {}

# GOOD: Enable pruning
automated:
  prune: true

2. Manual Sync Only:

# BAD: Requires manual intervention
syncPolicy: {}

# GOOD: Automated sync
syncPolicy:
  automated:
    prune: true
    selfHeal: true

3. Single Giant Application:

# BAD: One app for everything
# GOOD: Separate apps by component/service

4. No RBAC:

# GOOD: Always implement project-level RBAC
roles:
- name: developer
  policies:
  - p, proj:prod:dev, applications, sync, prod/*, allow

Approach

When implementing ArgoCD:

Start Simple: Deploy one application first

GitOps Everything: All config in Git

Automate: Enable auto-sync and self-heal

Organize: Use AppProjects for isolation

RBAC: Implement least-privilege access

Monitor: Set up notifications and alerts

Scale: Use ApplicationSets for multi-cluster/multi-env

Security: Enable SSO and audit logging

Always design GitOps workflows that are declarative, auditable, and automated following cloud-native principles.

Resources

ArgoCD Documentation: https://argo-cd.readthedocs.io/

GitOps Principles: https://opengitops.dev/

ApplicationSet: https://argocd-applicationset.readthedocs.io/

ArgoCD Notifications: https://argocd-notifications.readthedocs.io/

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