ArgoCD Reconciliation Loop

• ArgoCD operates a controller that runs in a reconciliation loop, constantly comparing live application state vs. stored application state, and reconciling the two.

• Drift detection happens out-of-the-box with ArgoCD. However, self-heal needs to be enabled for the drift to be fixed.

• On average, Argo takes 3 minutes to reconcile an app. The timeout is controlled via the ARGOCD_RECONCILIATION_TIMEOUT env var:

λ notes (main) $ k get deploy argocd-repo-server -oyaml |grep -i reconcil -A10
        - name: ARGOCD_RECONCILIATION_TIMEOUT
          valueFrom:
            configMapKeyRef:
              key: timeout.reconciliation
              name: argocd-cm
              optional: true

λ notes (main) $ k get cm argocd-cm -oyaml |grep -i reconciliation
  timeout.hard.reconciliation: 0s
  timeout.reconciliation: 180s

• You can also create a webhook in Github pointing to your ArgoCD instance. This way, when new code is pushed, Github will notify ArgoCD and ArgoCD will then reconcile the app.

Sync Policy

• Auto/Manual -
• Auto-prune resources - Describes what happens when files are deleted from the git repo
• Self-heal cluster - defines what actions argo will take when you manually update resources (with kubectl for example)
• You can also ignore certain properties within a spec. For example, to ignore changes to the replicaCount and configMap (config.yaml), add this to the Application spec:

    ignoreDifferences:
  # for the specified json pointers
  - group: apps
    kind: Deployment
    jsonPointers:
    - /spec/replicas
  - kind: ConfigMap
    jqPathExpressions:
    # Example: Ignore changes to a specific key inside a ConfigMap
    - '.data["config.yaml"]'
  # for the specified managedFields managers
  - group: "*"
    kind: "*"
    managedFieldsManagers:
    - kube-controller-manager
    # Name and namespace are optional. If specified, they must match exactly, these are not glob patterns.
    name: my-deployment
    namespace: my-namespace
  
  

  • note that you must also enable respectIgnoreDifferences:

        - RespectIgnoreDifferences=true # When syncing changes, respect fields ignored by the ignoreDifferences configuration