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Add description on Conflict on installing VolumePopulator CR for `V…
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…olumeSnapshotLink` across CSI drivers
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mkimuram committed Jun 10, 2022
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Expand Up @@ -91,6 +91,7 @@ tags, and then generate with `hack/update-toc.sh`.
- [Risks and Mitigations](#risks-and-mitigations)
- [Secret Handling](#secret-handling)
- [Security](#security)
- [Conflict on installing <code>VolumePopulator</code> CR for <code>VolumeSnapshotLink</code> across CSI drivers](#conflict-on-installing--cr-for--across-csi-drivers)
- [Design Details](#design-details)
- [Example flow of how this proposal works](#example-flow-of-how-this-proposal-works)
- [API](#api)
Expand Down Expand Up @@ -310,6 +311,15 @@ In addition, there will be cases that `ReferenceGrant` may be created/deleted/re
If all the processes succeed without any error, it succeeds even the `ReferenceGrant` is deleted in the middle of the processes.
If any errors happend in the processes and the controller retries, it may detect that there is no `ReferenceGrant` . Then, it won't use the `VolumeSnapshot` until the `ReferenceGrant` that allows the access is re-created.

#### Conflict on installing `VolumePopulator` CR for `VolumeSnapshotLink` across CSI drivers

This feature requires installing VolumePopulator` CR for `VolumeSnapshotLink` and is enabled per CSI driver basis.
Therefore, on enabling this feature for each CSI driver, it is expected that `VolumePopulator` CR for `VolumeSnapshotLink` is created before each CSI driver installation.
As a result, there may be a conflict in creating it for each driver, if there are any differences in their definitions, like alpha API and beta API.

To avoid this issue, it should be avoided to manage VolumePopulator` CR for `VolumeSnapshotLink` in each CSI driver's repository.
It should be managed in another single repository and the same CR should be used per cluster basis.

## Design Details

<!--
Expand Down Expand Up @@ -424,7 +434,7 @@ As a reference implementation, only (a) will be implemented in the community.

Regardless of the implementation,
- `VolumeSnapshotLink` CRD and `ReferenceGrant` CRD must exist in the cluster before the populator is deployed.
- `VolumePopulator` CRD to allow popluating from `VolumeSnapshotLink` CRD needs to be created to enable this feature, as AnyVolumeDataSource feature defines. The `VolumePopulator` CRD needed for this feature will be as follows:
- `VolumePopulator` CR to allow popluating from `VolumeSnapshotLink` CRD needs to be created to enable this feature, as AnyVolumeDataSource feature defines. The `VolumePopulator` CR needed for this feature will be as follows:
```yaml
kind: VolumePopulator
apiVersion: populator.storage.k8s.io/v1beta1
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