ArgoCD Applications¶

Creating Applications¶

Via UI¶

Click + NEW APP
Fill in details:
Application Name: my-app
Project: default
Sync Policy: Manual/Automatic
Repository URL: https://github.com/user/repo
Path: k8s/
Cluster: https://kubernetes.default.svc
Namespace: default
Click CREATE

Via CLI¶

argocd app create my-app \
  --repo https://github.com/user/repo.git \
  --path k8s/ \
  --dest-server https://kubernetes.default.svc \
  --dest-namespace default \
  --sync-policy automated \
  --auto-prune \
  --self-heal

Via YAML Manifest¶

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app
  namespace: argocd
spec:
  project: default

  source:
    repoURL: https://github.com/user/repo.git
    targetRevision: HEAD
    path: k8s/

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

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

Apply:

kubectl apply -f application.yaml

Application with Helm¶

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-helm-app
  namespace: argocd
spec:
  project: default

  source:
    repoURL: https://github.com/user/helm-charts.git
    targetRevision: HEAD
    path: charts/myapp
    helm:
      valueFiles:
        - values.yaml
        - values-prod.yaml
      parameters:
        - name: image.tag
          value: v1.0.0
        - name: replicaCount
          value: "3"
      values: |
        service:
          type: LoadBalancer
          port: 80

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

  syncPolicy:
    automated:
      prune: true
      selfHeal: true

Application with Kustomize¶

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-kustomize-app
  namespace: argocd
spec:
  project: default

  source:
    repoURL: https://github.com/user/repo.git
    targetRevision: HEAD
    path: overlays/production
    kustomize:
      images:
        - myapp=myapp:v1.0.0
      commonLabels:
        environment: production
      namePrefix: prod-

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

Sync Policies¶

Manual Sync¶

syncPolicy: {}  # No automated sync

Sync manually:

argocd app sync my-app

Automatic Sync¶

syncPolicy:
  automated:
    prune: false      # Don't delete resources
    selfHeal: false   # Don't auto-sync on cluster changes

Automatic with Prune and Self-Heal¶

syncPolicy:
  automated:
    prune: true       # Delete resources not in Git
    selfHeal: true    # Auto-sync on cluster changes
  syncOptions:
    - CreateNamespace=true
    - PruneLast=true

Sync Options¶

syncPolicy:
  syncOptions:
    - CreateNamespace=true        # Create namespace if not exists
    - PruneLast=true              # Prune resources last
    - ApplyOutOfSyncOnly=true     # Only sync out-of-sync resources
    - RespectIgnoreDifferences=true
    - ServerSideApply=true        # Use server-side apply

Sync Hooks¶

Pre-Sync Hook (Database Migration)¶

apiVersion: batch/v1
kind: Job
metadata:
  name: db-migration
  annotations:
    argocd.argoproj.io/hook: PreSync
    argocd.argoproj.io/hook-delete-policy: HookSucceeded
spec:
  template:
    spec:
      containers:
      - name: migrate
        image: myapp:v1.0.0
        command: ["./migrate.sh"]
      restartPolicy: Never

Post-Sync Hook (Smoke Tests)¶

apiVersion: batch/v1
kind: Job
metadata:
  name: smoke-tests
  annotations:
    argocd.argoproj.io/hook: PostSync
    argocd.argoproj.io/hook-delete-policy: HookSucceeded
spec:
  template:
    spec:
      containers:
      - name: test
        image: myapp:v1.0.0
        command: ["./smoke-tests.sh"]
      restartPolicy: Never

Sync-Fail Hook (Rollback)¶

apiVersion: batch/v1
kind: Job
metadata:
  name: rollback
  annotations:
    argocd.argoproj.io/hook: SyncFail
    argocd.argoproj.io/hook-delete-policy: HookSucceeded
spec:
  template:
    spec:
      containers:
      - name: rollback
        image: myapp:v1.0.0
        command: ["./rollback.sh"]
      restartPolicy: Never

Resource Hooks¶

Available hooks: - PreSync: Before sync - Sync: During sync - PostSync: After sync - SyncFail: On sync failure - Skip: Skip resource during sync

Delete policies: - HookSucceeded: Delete after success - HookFailed: Delete after failure - BeforeHookCreation: Delete before creating new hook

Health Assessment¶

Custom Health Check¶

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cm
  namespace: argocd
data:
  resource.customizations: |
    apps/Deployment:
      health.lua: |
        hs = {}
        if obj.status ~= nil then
          if obj.status.replicas ~= nil and obj.status.updatedReplicas ~= nil then
            if obj.status.replicas == obj.status.updatedReplicas then
              hs.status = "Healthy"
              hs.message = "All replicas are updated"
              return hs
            end
          end
        end
        hs.status = "Progressing"
        hs.message = "Waiting for rollout to finish"
        return hs

Ignore Differences¶

Ignore Specific Fields¶

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app
spec:
  ignoreDifferences:
  - group: apps
    kind: Deployment
    jsonPointers:
    - /spec/replicas
  - group: apps
    kind: StatefulSet
    jqPathExpressions:
    - .spec.volumeClaimTemplates[]?.metadata.annotations

App of Apps Pattern¶

Parent application managing child applications:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: app-of-apps
  namespace: argocd
spec:
  project: default

  source:
    repoURL: https://github.com/user/apps.git
    targetRevision: HEAD
    path: apps/

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

  syncPolicy:
    automated:
      prune: true
      selfHeal: true

Directory structure:

apps/
├── app1.yaml
├── app2.yaml
└── app3.yaml

ApplicationSet¶

Git Generator¶

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: microservices
  namespace: argocd
spec:
  generators:
  - git:
      repoURL: https://github.com/user/repo.git
      revision: HEAD
      directories:
      - path: services/*

  template:
    metadata:
      name: '{{path.basename}}'
    spec:
      project: default
      source:
        repoURL: https://github.com/user/repo.git
        targetRevision: HEAD
        path: '{{path}}'
      destination:
        server: https://kubernetes.default.svc
        namespace: '{{path.basename}}'
      syncPolicy:
        automated:
          prune: true
          selfHeal: true

List Generator¶

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: multi-env
  namespace: argocd
spec:
  generators:
  - list:
      elements:
      - cluster: dev
        url: https://dev.k8s.local
      - cluster: staging
        url: https://staging.k8s.local
      - cluster: prod
        url: https://prod.k8s.local

  template:
    metadata:
      name: 'myapp-{{cluster}}'
    spec:
      project: default
      source:
        repoURL: https://github.com/user/repo.git
        targetRevision: HEAD
        path: 'overlays/{{cluster}}'
      destination:
        server: '{{url}}'
        namespace: myapp

Cluster Generator¶

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: cluster-apps
  namespace: argocd
spec:
  generators:
  - clusters:
      selector:
        matchLabels:
          environment: production

  template:
    metadata:
      name: '{{name}}-myapp'
    spec:
      project: default
      source:
        repoURL: https://github.com/user/repo.git
        targetRevision: HEAD
        path: k8s/
      destination:
        server: '{{server}}'
        namespace: myapp

Managing Applications¶

Sync Application¶

# Sync application
argocd app sync my-app

# Sync specific resource
argocd app sync my-app --resource apps:Deployment:my-deployment

# Dry run
argocd app sync my-app --dry-run

# Force sync
argocd app sync my-app --force

Refresh Application¶

# Refresh (check Git for changes)
argocd app get my-app --refresh

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

Rollback Application¶

# List history
argocd app history my-app

# Rollback to specific revision
argocd app rollback my-app 5

Delete Application¶

# Delete application (keep resources)
argocd app delete my-app

# Delete application and resources
argocd app delete my-app --cascade

# Delete without confirmation
argocd app delete my-app --yes

Patch Application¶

# Patch application
argocd app patch my-app --patch '{"spec":{"source":{"targetRevision":"v2.0.0"}}}'

# Patch with file
argocd app patch my-app --patch-file patch.yaml

Application Status¶

View Status¶

# Get application details
argocd app get my-app

# Get application tree
argocd app get my-app --show-operation

# Get application resources
argocd app resources my-app

View Logs¶

# View application logs
argocd app logs my-app

# Follow logs
argocd app logs my-app --follow

# View specific container logs
argocd app logs my-app --container my-container

View Diff¶

# Show diff between Git and cluster
argocd app diff my-app

# Show diff for specific resource
argocd app diff my-app --resource apps:Deployment:my-deployment

Best Practices¶

✅ Use Projects: Organize applications into projects ✅ Enable Auto-Sync Carefully: Manual for prod, auto for dev/staging ✅ Use Sync Waves: Control deployment order with annotations ✅ Implement Health Checks: Custom health checks for CRDs ✅ Use Hooks: Pre/post sync hooks for migrations and tests ✅ Ignore Differences: Ignore fields that change frequently ✅ Use App of Apps: Manage multiple applications ✅ Use ApplicationSets: Deploy to multiple clusters/environments ✅ Monitor Sync Status: Set up alerts for OutOfSync apps ✅ Version Control: All manifests in Git

Next Steps¶

Continue to: - ArgoCD-Advanced.md - Multi-cluster, RBAC, SSO - ArgoCD-Examples.md - Real-world examples