Add multiple label selector support to Velero backup /restore API
add initial design for enabling multiple label support for backing up resources Signed-off-by: Shubham Pampattiwar <shubhampampattiwar7@gmail.com> update solution approach Signed-off-by: Shubham Pampattiwar <shubhampampattiwar7@gmail.com> add restore API bits Signed-off-by: Shubham Pampattiwar <shubhampampattiwar7@gmail.com> remove CLI bits and update examples Signed-off-by: Shubham Pampattiwar <shubhampampattiwar7@gmail.com> update spec name to OrLabelSelector Signed-off-by: Shubham Pampattiwar <shubhampampattiwar7@gmail.com> update high level design Signed-off-by: Shubham Pampattiwar <shubhampampattiwar7@gmail.com>pull/4619/head
Shubham Pampattiwar
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# Ensure support for backing up resources based on multiple labels
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## Abstract
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As of today Velero supports filtering of resources based on single label selector per backup. It is desired that Velero
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support backing up of resources based on multiple labels (OR logic).
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**Note:** This solution is required because kubernetes label selectors only allow AND logic of labels.
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## Background
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Currently, Velero's Backup/Restore API has a spec field `LabelSelector` which helps in filtering of resources based on
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a **single** label value per backup/restore request. For instance, if the user specifies the `Backup.Spec.LabelSelector` as
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`data-protection-app: true`, Velero will grab all the resources that possess this label and perform the backup
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operation on them. The `LabelSelector` field does not accept more than one labels, and thus if the user want to take
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backup for resources consisting of a label from a set of labels (label1 OR label2 OR label3) then the user needs to
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create multiple backups per label rule. It would be really useful if Velero Backup API could respect a set of
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labels (OR Rule) for a single backup request.
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Related Issue: https://github.com/vmware-tanzu/velero/issues/1508
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## Goals
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- Enable support for backing up resources based on multiple labels (OR Logic) in a single backup config.
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- Enable support for restoring resources based on multiple labels (OR Logic) in a single restore config.
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## Use Case/Scenario
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Let's say as a Velero user you want to take a backup of secrets, but all these secrets do not have one single consistent
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label on them. We want to take backup of secrets having any one label in `app=gdpr`, `app=wpa` and `app=ccpa`. Here
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we would have to create 3 instances of backup for each label rule. This can become cumbersome at scale.
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## High-Level Design
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### Addition of `OrLabelSelectors` spec to Velero Backup/Restore API
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For Velero to back up resources if they consist of any one label from a set of labels, we would like to add a new spec
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field `OrLabelSelectors` which would enable user to specify them. The Velero backup would somewhat look like:
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```
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apiVersion: velero.io/v1
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kind: Backup
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metadata:
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name: backup-101
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namespace: openshift-adp
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spec:
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includedNamespaces:
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- test
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storageLocation: velero-sample-1
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ttl: 720h0m0s
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orLabelSelectors:
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- matchLabels:
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app=gdpr
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- matchLabels:
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app=wpa
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- matchLabels:
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app=ccpa
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```
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**Note:** This approach will **not** be changing any current behavior related to Backup API spec `LabelSelector`. Rather we
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propose that the label in `LabelSelector` spec and labels in `OrLabelSelectors` should be treated as different Velero functionalities.
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Both these fields will be treated as separate Velero Backup API specs. If `LabelSelector` (singular) is present then just match that label.
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And if `OrLabelSelectors` is present then match to any label in the set specified by the user. For backup case, if both the `LabelSelector` and `OrLabelSelectors`
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are specified (we do not anticipate this as a real world use-case) then the `OrLabelSelectors` will take precedence, `LabelSelector` will
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only be used to filter only when `OrLabelSelectors` is not specified by the user. This helps to keep both spec behaviour independent and not confuse the users.
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This way we preserve the existing Velero behaviour and implement the new functionality in a much cleaner way.
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For instance, let's take a look the following cases:
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1. Only `LabelSelector` specified: Velero will create a backup with resources matching label `app=protect-db`
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```
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apiVersion: velero.io/v1
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kind: Backup
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metadata:
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name: backup-101
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namespace: openshift-adp
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spec:
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includedNamespaces:
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- test
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storageLocation: velero-sample-1
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ttl: 720h0m0s
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labelSelector:
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- matchLabels:
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app=gdpr
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```
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2. Only `OrLabelSelectors` specified: Velero will create a backup with resources matching any label from set `{app=gdpr, app=wpa, app=ccpa}`
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```
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apiVersion: velero.io/v1
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kind: Backup
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metadata:
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name: backup-101
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namespace: openshift-adp
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spec:
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includedNamespaces:
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- test
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storageLocation: velero-sample-1
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ttl: 720h0m0s
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orLabelSelectors:
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- matchLabels:
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app=gdpr
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- matchLabels:
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app=wpa
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- matchLabels:
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app=ccpa
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```
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Similar implementation will be done for the Restore API as well.
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## Detailed Design
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With the Introduction of `OrLabelSelectors` the BackupSpec and RestoreSpec will look like:
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BackupSpec:
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```
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type BackupSpec struct {
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[...]
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// OrLabelSelectors is a set of []metav1.LabelSelector to filter with
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// when adding individual objects to the backup. Resources matching any one
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// label from the set of labels will be added to the backup. If empty
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// or nil, all objects are included. Optional.
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// +optional
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OrLabelSelectors []\*metav1.LabelSelector
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[...]
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}
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```
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RestoreSpec:
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```
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type RestoreSpec struct {
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[...]
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// OrLabelSelectors is a set of []metav1.LabelSelector to filter with
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// when restoring objects from the backup. Resources matching any one
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// label from the set of labels will be restored from the backup. If empty
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// or nil, all objects are included from the backup. Optional.
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// +optional
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OrLabelSelectors []\*metav1.LabelSelector
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[...]
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}
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```
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The logic to collect resources to be backed up for a particular backup will be updated in the `backup/item_collector.go`
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around [here](https://github.com/vmware-tanzu/velero/blob/574baeb3c920f97b47985ec3957debdc70bcd5f8/pkg/backup/item_collector.go#L294).
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And for filtering the resources to be restored, the changes will go [here](https://github.com/vmware-tanzu/velero/blob/d1063bda7e513150fd9ae09c3c3c8b1115cb1965/pkg/restore/restore.go#L1769)
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**Note:**
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- This feature will not be exposed via Velero CLI.
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