Add Design for Allowing Object-Level Resource Status Restore

changelogs/unreleased/8403-shubham-pampattiwar

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+Add Design for Allowing Object-Level Resource Status Restore

design/resource-status-restore.md

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+# Allow Object-Level Resource Status Restore in Velero
+
+## Abstract
+This design proposes a way to enhance Velero’s restore functionality by enabling object-level resource status restoration through annotations. 
+Currently, Velero allows restoring resource statuses only at a resource type level, which lacks granularity of restoring the status of specific resources. 
+By introducing an annotation that controllers can set on individual resource objects, this design aims to improve flexibility and autonomy for users/resource-controllers, providing a more way
+to enable resource status restore.
+
+
+## Background
+Velero provides the `restoreStatus` field in the Restore API to specify resource types for status restoration. However, this feature is limited to resource types as a whole, lacking the granularity needed to restore specific objects of a resource type. Resource controllers, especially those managing custom resources with external dependencies, may need to restore status on a per-object basis based on internal logic and dependencies.
+
+This design adds an annotation-based approach to allow controllers to specify status restoration at the object level, enabling Velero to handle status restores more flexibly.
+
+## Goals
+- Provide a mechanism to specify the restoration of a resource’s status at an object level.
+- Maintain backwards compatibility with existing functionality, allowing gradual adoption of this feature.
+- Integrate the new annotation-based objects-level status restore with Velero’s existing resource-type-level `restoreStatus` configuration.
+
+## Non-Goals
+- Alter Velero’s existing resource type-level status restoration mechanism for resources without annotations.
+
+## Use-Cases/Scenarios
+
+1. Controller managing specific Resources
+  - A resource controller identifies that a specific object of a resource should have its status restored due to particular dependencies
+  - The controller automatically sets the `velero.io/restore-status: true` annotation on the resource.
+  - During restore, Velero restores the status of this object, while leaving other resources unaffected.
+  - The status for the annotated object will be restored regardless of its inclusion/exclusion in `restoreStatus.includedResources`
+
+2. A specific object must not have its status restored even if its included in `restoreStatus.includedResources`
+  - A user specifies a resource type in the `restoreStatus.includedResources` field within the Restore custom resource.
+  - A particular object of that resource type is annotated with `velero.io/restore-status: false` by the user.
+  - The status of the annotated object will not restored even though its included in `restoreStatus.includedResources` because annotation is `false` and it takes precedence.
+
+4. Default Behavior for objects Without the Annotation
+  - Objects without the `velero.io/restore-status` annotation behave as they currently do: Velero skips their status restoration unless the resource type is specified in the `restoreStatus.includedResources` field.
+
+## High-Level Design
+
+- Object-Level Status Restore Annotation: We are introducing the `velero.io/restore-status` annotation at the resource object level to mark specific objects for status restoration.
+  - `true`: Indicates that the status should be restored for this object
+  - `false`: Skip restoring status for this specific object
+  - Invalid or missing annotations defer to the meaning of existing resource type-level logic.
+
+- Restore logic precedence: 
+  - Annotations take precedence when they exist with valid values (`true` or `false`).
+  - Restore spec `restoreStatus.includedResources` is only used when annotations are invalid or missing.
+
+- Velero Restore Logic Update: During a restore operation, Velero will:
+  - Extend the existing restore logic to parse and prioritize annotations introduced in this design.
+  - Update resource objects accordingly based on their annotation values or fallback configuration.
+
+
+## Detailed Design
+
+- Annotation for object-Level Status Restore: The `velero.io/restore-status` annotation will be set on individual resource objects by users/controllers as needed:
+```yaml
+metadata:
+  annotations:
+    velero.io/restore-status: "true"
+```
+
+- Restore Logic Modifications: During the restore operation, the restore controller will follow these steps:
+   - Parse the `restoreStatus.includedResources` spec to determine resource types eligible for status restoration.
+   - For each resource object:
+     - Check for the `velero.io/restore-status` annotation.
+     - If the annotation value is:
+       - `true`: Restore the status of the object
+       - `false`: Skip restoring the status of the object
+     - If the annotation is invalid or missing:
+       - Default to the `restoreStatus.includedResources` configuration
+
+
+## Implementation
+
+We are targeting the implementation of this design for Velero 1.16 release.
+
+Current restoreStatus logic resides here: https://github.com/vmware-tanzu/velero/blob/32a8c62920ad96c70f1465252c0197b83d5fa6b6/pkg/restore/restore.go#L1652
+
+The modified logic would look somewhat like:
+
+```go
+// Determine whether to restore status from resource type configuration
+shouldRestoreStatus := ctx.resourceStatusIncludesExcludes != nil && ctx.resourceStatusIncludesExcludes.ShouldInclude(groupResource.String())
+
+// Check for object-level annotation
+annotations := obj.GetAnnotations()
+objectAnnotation := annotations["velero.io/restore-status"]
+annotationValid := objectAnnotation == "true" || objectAnnotation == "false"
+
+// Determine restore behavior based on annotation precedence
+shouldRestoreStatus = (annotationValid && objectAnnotation == "true") || (!annotationValid && shouldRestoreStatus)
+
+ctx.log.Debugf("status field for %s: exists: %v, should restore: %v (by annotation: %v)", newGR, statusFieldExists, shouldRestoreStatus, annotationValid)
+
+if shouldRestoreStatus && statusFieldExists {
+    if err := unstructured.SetNestedField(obj.Object, objStatus, "status"); err != nil {
+        ctx.log.Errorf("Could not set status field %s: %v", kube.NamespaceAndName(obj), err)
+        errs.Add(namespace, err)
+        return warnings, errs, itemExists
+    }
+    obj.SetResourceVersion(createdObj.GetResourceVersion())
+    updated, err := resourceClient.UpdateStatus(obj, metav1.UpdateOptions{})
+    if err != nil {
+        ctx.log.Infof("Status field update failed %s: %v", kube.NamespaceAndName(obj), err)
+        warnings.Add(namespace, err)
+	} else {
+        createdObj = updated
+    }
+}
+```
+