Bucket versioning

Versioning (version control) is a mechanism that lets a bucket store the history of an object's changes as a set of its versions. Versioning is enabled at the bucket level and applies to all objects inside it.

In buckets with versioning enabled, the VK Object Storage service works as follows:

• If you try to overwrite an object, a new version of the object appears in the bucket, but the previous version is not deleted.
• If VK Object Storage receives several requests to write the same object at the same time, it stores all the received versions of the object in the bucket.
• If you try to delete an object from the bucket, VK Object Storage adds a delete marker to the bucket and makes it the current version of the object. Previous versions remain in the bucket but are unavailable via a GET request to the object.

As a result, no changes to objects in the bucket are lost. This simplifies recovering data that was deleted or damaged due to unintended user actions or application errors.

• Unversioned.

  New buckets created without enabling versioning, as well as buckets created before versioning was implemented in VK Object Storage, have no versioning status. For all objects in these buckets, the version ID is null.

• Versioning-enabled.

  Versioning is enabled either when the bucket is created or afterwards, in the control panel or via the AWS CLI. Enabling versioning does not change existing objects in the bucket — they keep the null version ID. After it's enabled, every new object uploaded to the bucket, or every new version of an existing object, gets a unique version ID.

  Once you enable versioning, you cannot disable it — you can only suspend it.

• Versioning-suspended.

  Suspending versioning stops the creation of new object versions. While versioning is suspended:

  • Existing object versions in the bucket are not changed.
  • New objects or new versions of existing objects uploaded to the bucket get the null version ID.
  • If the bucket already has an object version with the null ID and you upload an object with the same key, it overwrites the existing null version.

A version ID is a string of characters that VK Object Storage automatically generates when an object is uploaded to a bucket.

If versioning is enabled for a bucket, objects get a unique version ID on upload. If versioning is not enabled or is suspended, uploaded objects get the null version ID.

You can use a version ID in a URL, since it contains only unreserved characters: Latin letters, digits, and the -, ., _, ~ characters.

A delete marker is a special version of an object that VK Object Storage adds to a versioning-enabled bucket when you delete an object from it. Like any other object, a delete marker has a key and a version ID, but no content. The key of the object you delete becomes the key of the delete marker, and the delete marker itself becomes the current version of the object. The other versions of the object are not changed.

Although the object technically remains in the bucket, VK Object Storage treats it as deleted. For example, a GET request to the object returns a 404 (Not Found) error.

A delete marker does not disappear from a versioning-enabled bucket even if the deleted object is later overwritten, so an object can have several delete markers in its version history.

You can delete a delete marker from an object's version history with a DELETE request that specifies the version ID of that delete marker.

Creating a delete marker does not depend on object lock: a marker is added even if the current version of the object is protected, because the protected version itself is not deleted or changed.

The result of adding an object to a bucket depends on the bucket's versioning status:

• Versioning enabled: a new version of the object is created, differing from the previous one by its version ID and a later creation time.
• Versioning suspended: a new version of the object is created with the null version ID. If a version with the null ID already exists, it is overwritten.
• No versioning: the new object gets the null version ID. If the object already exists in the bucket, it is overwritten.

The result of deletion depends on the bucket's versioning status and whether a version ID is specified in the delete request.

Versioning enabled:

• No version ID specified: a delete marker is created and becomes the current version of the object. Existing versions are not changed. This happens even if object lock is set on the current version of the object, since the version itself is not actually deleted.

• Version ID specified and object lock disabled: the object version or delete marker with the specified ID is deleted. If it is the only version, deleting it permanently removes the object from the bucket.

• Version ID specified and object lock enabled: the object cannot be deleted until the retention period expires or the legal hold is removed.

  Users with WRITE permissions can bypass the retention period in managed mode (GOVERNANCE).

Versioning suspended:

• No version ID specified: the object version with the null ID, if it exists, is deleted, and a delete marker is created and becomes the current version of the object.
• Version ID specified: the object version or delete marker with the specified ID is deleted. If it is the only version, deleting it permanently removes the object from the bucket.

No versioning:

• No version ID specified: the object is permanently deleted from the bucket.
• Version ID specified: a 204 response is returned, since no such object version exists.