Object versioning

You can store multiple versions of your content so that you can recover from unintended overwrites. Object versioning is an easy way to implement version control, which you can use with any type of content.

Note

You cannot version a large-object manifest file, but the large-object manifest file can point to versioned segments.

It is strongly recommended that you put non-current objects in a different container than the container where current object versions reside.

To enable object versioning, the cloud provider sets the allow_versions option to TRUE in the container configuration file.

The X-Versions-Location header defines the container that holds the non-current versions of your objects. You must UTF-8-encode and then URL-encode the container name before you include it in the X-Versions-Location header. This header enables object versioning for all objects in the container. With a comparable archive container in place, changes to objects in the current container automatically create non-current versions in the archive container.

Here’s an example:

1. Create the current container:

# curl -i $publicURL/current -X PUT -H "Content-Length: 0" -H "X-Auth-Token: $token" -H "X-Versions-Location: archive"

HTTP/1.1 201 Created
Content-Length: 0
Content-Type: text/html; charset=UTF-8
X-Trans-Id: txb91810fb717347d09eec8-0052e18997
Date: Thu, 23 Jan 2014 21:28:55 GMT

1. Create the first version of an object in the current container:

   # curl -i $publicURL/current/my_object --data-binary 1 -X PUT -H "Content-Length: 0" -H "X-Auth-Token: $token"
   

   HTTP/1.1 201 Created
   Last-Modified: Thu, 23 Jan 2014 21:31:22 GMT
   Content-Length: 0
   Etag: d41d8cd98f00b204e9800998ecf8427e
   Content-Type: text/html; charset=UTF-8
   X-Trans-Id: tx5992d536a4bd4fec973aa-0052e18a2a
   Date: Thu, 23 Jan 2014 21:31:22 GMT

   Nothing is written to the non-current version container when you initially PUT an object in the current container. However, subsequent PUT requests that edit an object trigger the creation of a version of that object in the archive container.

   These non-current versions are named as follows:

   <length><object_name><timestamp>

   Where length is the 3-character, zero-padded hexadecimal character length of the object, <object_name> is the object name, and <timestamp> is the time when the object was initially created as a current version.

2. Create a second version of the object in the current container:

   # curl -i $publicURL/current/my_object --data-binary 2 -X PUT -H "Content-Length: 0" -H "X-Auth-Token: $token"
   

   HTTP/1.1 201 Created
   Last-Modified: Thu, 23 Jan 2014 21:41:32 GMT
   Content-Length: 0
   Etag: d41d8cd98f00b204e9800998ecf8427e
   Content-Type: text/html; charset=UTF-8
   X-Trans-Id: tx468287ce4fc94eada96ec-0052e18c8c
   Date: Thu, 23 Jan 2014 21:41:32 GMT

3. Issue a GET request to a versioned object to get the current version of the object. You do not have to do any request redirects or metadata lookups.

   List older versions of the object in the archive container:

   # curl -i $publicURL/archive?prefix=009my_object -X GET -H "X-Auth-Token: $token"
   

   HTTP/1.1 200 OK
   Content-Length: 30
   X-Container-Object-Count: 1
   Accept-Ranges: bytes
   X-Timestamp: 1390513280.79684
   X-Container-Bytes-Used: 0
   Content-Type: text/plain; charset=utf-8
   X-Trans-Id: tx9a441884997542d3a5868-0052e18d8e
   Date: Thu, 23 Jan 2014 21:45:50 GMT
   
   009my_object/1390512682.92052

Note

A POST request to a versioned object updates only the metadata for the object and does not create a new version of the object. New versions are created only when the content of the object changes.

1. Issue a DELETE request to a versioned object to remove the current version of the object and replace it with the next-most current version in the non-current container.

   # curl -i $publicURL/current/my_object -X DELETE -H "X-Auth-Token: $token"
   

   HTTP/1.1 204 No Content
   Content-Length: 0
   Content-Type: text/html; charset=UTF-8
   X-Trans-Id: tx006d944e02494e229b8ee-0052e18edd
   Date: Thu, 23 Jan 2014 21:51:25 GMT

   List objects in the archive container to show that the archived object was moved back to the current container:

   # curl -i $publicURL/archive?prefix=009my_object -X GET -H "X-Auth-Token: $token"
   

   HTTP/1.1 204 No Content
   Content-Length: 0
   X-Container-Object-Count: 0
   Accept-Ranges: bytes
   X-Timestamp: 1390513280.79684
   X-Container-Bytes-Used: 0
   Content-Type: text/html; charset=UTF-8
   X-Trans-Id: tx044f2a05f56f4997af737-0052e18eed
   Date: Thu, 23 Jan 2014 21:51:41 GMT

   This next-most current version carries with it any metadata last set on it. If want to completely remove an object and you have five versions of it, you must DELETE it five times.

2. To disable object versioning for the current container, remove its X-Versions-Location metadata header by sending an empty key value.

   # curl -i $publicURL/current -X PUT -H "Content-Length: 0" -H "X-Auth-Token: $token" -H "X-Versions-Location: "
   

   HTTP/1.1 202 Accepted
   Content-Length: 76
   Content-Type: text/html; charset=UTF-8
   X-Trans-Id: txe2476de217134549996d0-0052e19038
   Date: Thu, 23 Jan 2014 21:57:12 GMT
   
   <html><h1>Accepted</h1><p>The request is accepted for processing.</p></html>