docs: Add documentation on background cascading deletion (argoproj#12229

) (argoproj#14150)

Signed-off-by: toyamagu2021@gmail.com <toyamagu2021@gmail.com>
Co-authored-by: toyamagu <83329336+toyamagu-2021@users.noreply.github.com>

docs/operator-manual/application.yaml

@@ -6,7 +6,10 @@ metadata:
   namespace: argocd
   # Add this finalizer ONLY if you want these to cascade delete.
   finalizers:
+    # The default behaviour is foreground cascading deletion
     - resources-finalizer.argocd.argoproj.io
+    # Alternatively, you can use background cascading deletion
+    # - resources-finalizer.argocd.argoproj.io/background
   # Add labels to your application object.
   labels:
     name: guestbook

docs/user-guide/app_deletion.md

@@ -43,11 +43,18 @@ kubectl delete app APPNAME
 ```yaml
 metadata:
   finalizers:
+    # The default behaviour is foreground cascading deletion
     - resources-finalizer.argocd.argoproj.io
+    # Alternatively, you can use background cascading deletion
+    # - resources-finalizer.argocd.argoproj.io/background
 ```
 
 When deleting an Application with this finalizer, the Argo CD application controller will perform a cascading delete of the Application's resources.
 
 Adding the finalizer enables cascading deletes when implementing [the App of Apps pattern](../operator-manual/cluster-bootstrapping.md#cascading-deletion).
 
+The default propagation policy for cascading deletion is [foreground cascading deletion](https://kubernetes.io/docs/concepts/architecture/garbage-collection/#foreground-deletion).
+ArgoCD performs [background cascading deletion](https://kubernetes.io/docs/concepts/architecture/garbage-collection/#background-deletion) when `resources-finalizer.argocd.argoproj.io/background` is set.
+
 When you invoke `argocd app delete` with `--cascade`, the finalizer is added automatically.
+You can set the propagation policy with `--propagation-policy <foreground|background>`.