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Object versioning

Using the Swift API, you have the option to retain multiple versions of an object, rather than overwriting it in place.

Prerequisites

In order to manage object versioning, be sure that you have installed and configured the swift command-line interface (CLI). There is presently no way to set object expiry with the openstack CLI.

Also, ensure that you have configured a private container, i.e. one with an empty Read ACL. The examples in this how-to guide assume that your container is named private-container, and that it presently contains a single object named testobj.txt.

Creating a container for non-current versioned objects

In addition to the container holding your live objects, private-container, you will also need one for your prior versions. In this example, we use the name private-container-versions for that container:

swift post private-container-versions
This command produces no output.

Setting X-Versions-Location

You must next set the X-Versions-Location header on the original container:

swift post -H "X-Versions-Location: private-container-versions" private-container

Testing object versioning

You can now verify that object versioning is working correctly.

  1. Upload a new version of testobj.txt: 
    $ echo "bye bye" > testobj.txt
$ swift upload private-container testobj.txt
  2. Observe that there is now a newly created object in the private-container-versions container: 
    $ swift list private-container-versions
00btestobj.txt/1670250073.717985
  3. Issue a command to delete the object: 
    $ swift delete private-container testobj.txt
testobj.txt
  4. Read back the object. Since the container is now versioned, the “deletion” in step 3 only caused a roll-back to the object’s prior state: 
    $ swift download -o - private-container testobj.txt
hello world

Object versioning does not prevent deleting the last remaining (i.e. first created) version of an object. Do not use object versioning as a prevention mechanism for inadvertent object deletion; it is not suitable for that purpose.