AWS : S3 (Simple Storage Service) III - Bucket Versioning

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Creating and deleting S3

Versioning allows us to preserve, retrieve, and restore every version of every file in an Amazon S3 bucket. Once we enable Versioning for a bucket, Amazon S3 preserves existing files anytime we overwrite or delete them.

This provides an additional level of protection by providing a means of recovery for accidental overwrites or expirations. Versioning-enabled buckets store all versions of our objects by default.

Versioning is a means of keeping multiple variants of an object in the same bucket. We can use Lifecycle rules to manage all versions of our objects as well as their associated costs. Lifecycle rules enable us to automatically archive our objects to the Glacier Storage Class and/or remove them after a specified time period.

Once enabled, Versioning cannot be disabled, only suspended.

Image source : Amazon Simple Storage Service

In one bucket, for example, we can have two objects with the same key, but different version IDs, such as photo.gif (version 111111) and photo.gif (version 121212).

Versioning-enabled buckets enable us to recover objects from accidental deletion or overwrite. For example:

If we delete an object, instead of removing it permanently, Amazon S3 inserts a delete marker, which becomes the current object version. We can always restore the previous version.
If we overwrite an object, it results in a new object version in the bucket. We can always restore the previous version.

Buckets can be in one of three states:

unversioned (the default)
versioning-enabled
versioning-suspended

The versioning state applies to all of the objects in that bucket. The first time we enable a bucket for versioning, objects in it are thereafter always versioned and given a unique version ID:

Objects stored in our bucket before we set the versioning state have a version ID of null. When we enable versioning, existing objects in our bucket do not change. What changes is how Amazon S3 handles the objects in future requests.
The bucket owner (or any user with appropriate permissions) can suspend versioning to stop accruing object versions. When we suspend versioning, existing objects in our bucket do not change. What changes is how Amazon S3 handles objects in future requests.

Configuring versioning

We can configure bucket versioning using any of the following methods:

Configure versioning using the Amazon S3 console
Configure versioning programmatically using the AWS SDKs

Each bucket we create has a versioning subresource (see Bucket Configuration Options) associated with it. By default, our bucket is unversioned, and accordingly the versioning subresource stores empty versioning configuration.

<VersioningConfiguration xmlns="http://s3.amazonaws.com/doc/2015-03-01/">
</VersioningConfiguration>

To enable versioning, we send a request to Amazon S3 with a versioning configuration that includes a status.

<VersioningConfiguration xmlns="http://s3.amazonaws.com/doc/2015-03-01/">
  <Status>Enabled</Status> 
</VersioningConfiguration>

To suspend versioning, we set the status value to Suspended.

Enabling Bucket Versioning

To enable versioning on a bucket:

Sign in to the AWS Management Console and open the Amazon S3 console at https://console.aws.amazon.com/s3/.
In the Buckets list, click the details icon on the left of the bucket name and then click Properties to display bucket properties.
In the Properties pane, click Versioning and then click Enable Versioning.

After we enable versioning on a bucket, it can be in only the enabled or suspended state; we cannot disable versioning on a bucket. If we suspend versioning, Amazon S3 suspends the creation of object versions for all operations, but preserves any existing object versions.

Managing Objects in a Versioning-Enabled Bucket

A versioning-enabled bucket can have multiple versions of objects in the bucket. Amazon S3 assigns each object a unique version ID.

When a bucket is versioning-enabled, we can show or hide all the object versions. The following example shows the list of objects in the bogotobogo-bucket bucket. Version information is hidden, so these objects represent the latest version.

If we click Show, the console lists all the versions, as shown in the following example.

For each object version, the console shows a unique version ID, the date and time the object version was created, and other properties. Note that the files have already been put into the bucket before we enabled versioning. That's why we have nulls in Version ID column.

Uploading an Object

If we add a new file, we can see the newly added file has Version ID unlike the files before we Enabled Versioning.

If we upload an object with a key name that already exists in the bucket, Amazon S3 creates another version of the object instead of replacing the existing object. bogo1.txt:

Updating Object Properties

If we update any object properties after the initial object upload, such as changing the storage details or any other metadata changes, then Amazon S3 creates a new object version in the bucket. If we rename the object, Amazon S3 creates a new object version.

For example, if we update an object's storage class or change how the object is stored at rest by updating its server-side encryption property, Amazon S3 creates an object version for each property update we save.

When versions are hidden, we can update all the object properties; when versions are shown, we can update only the permissions for the specific object version.

Deleting Objects from a Versioning-Enabled Bucket

In a versioning-enabled bucket, we can either delete an object from the object list (version information hidden).

With version information hidden, the console shows the object list as shown in the following example:

or delete a specific version of the object.

If we select and delete the bogo4.txt object, Amazon S3 adds a delete marker for the object and the object no longer appears in the object list:

To delete an object permanently, we must delete all the versions of the object, including the delete marker (if present). If we delete only a specific object version, Amazon S3 permanently deletes only that specific version. If we delete the delete marker, the object reappears in the object list.

Restoring Previous Versions

AWS S3 versioning operations are based on stack data structure.
We can enable versioning by clicking 'Enable Version' button under 'Properties'.
There are two ways of restoring previous versions: Restoring Previous Versions
1. Deleting the more recent versions.
2. Put the previous version on top (re-uploading after copy(download))
Testing Results - Restoring previous version works as expected.
1. Performed in console mode.
2. We can test the versioning using multiple text files with the same name but with different content, for example, version 1, version2, etc.
3. We can simulate GET method by downloading the 'test1' with 'Hide' on.
  1. Method 1 (Deletion) Delete the top (v.4) => We get previous version (v.3)
  2. Method 2 (Copying) Copying the previous version (v.3) , and put it on top of v4 by uploading it. => We get v.3