Proposal to add include exclude policy to resource policy

This enhancement will allow the user to set include and exclude filters for resources in a resource policy configmap, so that these filters are reusable and the user will not need to set them each time they create a backup.

Background

As mentioned in issue #8610. When there's a long list of resources to include or exclude in a backup, it can be cumbersome to set them each time a backup is created. There's a requirement to set these filters in a separate data structure so that they can be reused in multiple backups.

High-Level Design

We may extend the data structure of resource policy to add includeExcludePolicy, which include the include and exclude filters in the BackupSpec. When the user creates a backup which references the resource policy config velero backup create --resource-policies-configmap <configmap-name>, the filters in "includeExcludePolicy" will take effect to filter the resources when velero collects the resources to backup.

Detailed Design

Data Structure

The map includeExcludePolicy contains four fields includedClusterScopedResources, excludedClusterScopedResources, includedNamespaceScopedResources,excludedNamespaceScopedResources. These filters work exactly as the filters defined BackupSpec with the same names. An example of the policy looks like:

#omitted other irrelevant fields like 'version', 'volumePolicies'
includeExcludePolicy:
  includedClusterScopedResources:
    - "cr"
    - "crd"
    - "pv"
  excludedClusterScopedResources:
    - "volumegroupsnapshotclass"
    - "ingressclass"
  includedNamespaceScopedResources:
    - "pod"
    - "service"
    - "deployment"
    - "pvc"
  excludedNamespaceScopedResources:
    - "configmap"

These filters are in the form of scoped include/exclude filters, which by design will not work with the "old" resource filters. Therefore, when a Backup references a resource policy configmap which has includeExcludePolicy, and at the same time it has the "old" resource filters, i.e. includedResources, excludedResources, includeClusterResources set in the BackupSpec, the Backup will fail with a validation error.

Priorities

A user may set the include/exclude filters in Backupspec and also in the resource policy configmap. In this case, the filters in both the Backupspec and the resource policy configmap will take effect. When there's a conflict, the filters in the Backupspec will take precedence. For example, if resource X is in the list of includedNamespaceScopedResources filter in the Backupspec, but it's also in the list of excludedClusterScopedResources in the resource policy configmap, then resource X will be included in the backup. In this way, users can set the filters in the resource policy configmap to cover most of their use cases, and then override them in the Backupspec when needed.

Implementation

In addition to the data structure change, we will need to implement the following changes:

1. A new function CombineWithPolicy will be added to the struct ScopeIncludesExcludes, which will combine the include/exclude filters in the resource policy configmap with the include/exclude filters in the Backupspec:

func (ie *ScopeIncludesExcludes) CombineWithPolicy(policy resourcepolicies.IncludeExcludePolicy) {
	mapFunc := scopeResourceMapFunc(ie.helper)
	for _, item := range policy.ExcludedNamespaceScopedResources {
		resolvedItem := mapFunc(item, true)
		if resolvedItem == "" {
			continue
		}
		if !ie.ShouldInclude(resolvedItem) && !ie.ShouldExclude(resolvedItem) {
			// The existing includeExcludes in the struct has higher priority, therefore, we should only add the item to the filter
			// when the struct does not include this item and this item is not yet in the excludes filter.
			ie.namespaceScopedResourceFilter.excludes.Insert(resolvedItem)
		}
		
	}
.....

This function will be called in the kubernetesBackupper.BackupWithResolvers function, to make sure the combined ScopeIncludesExcludes filter will be assigned to the ResourceIncludesExcludes filter of the Backup request.

2. Extra validation code will be added to the function prepareBackupRequest of BackupReconciler to check if there are "old" Resource filters in the BackupSpec when the Backup references a resource policy configmap which has includeExcludePolicy.

Alternatives Considered

We may put includeExcludePolicy in a separate configmap, but it will require adding extra field to BackupSpec to reference the configmap, which is not necessary.