Bug 1404347

Document URL: 
https://docs.openshift.com/container-platform/3.3/dev_guide/managing_images.html

Section Number and Name: 
New subsection of the tagging images section

Describe the issue: 
There is not much guidance on the best way to tag images. This causes some customers to tag every new version of an image with a unique tag, for instance:
myimage:dec132016105845
To indicate this image revision is tagged on dec13, 2016 at 10:58:45. This seems like a nice idea as it makes it obvious which revision is which; however, it leads to issues where old image metadata never gets pruned from etcd. If you use the above schema to tag images for every change, then running `oadm prune image` commands will never prune images, as each one is considered the newest revision in a separate tag. In reality, one should keep multiple revisions to a single unchanging tag, or a few unchanging tags:

myimage:latest
myimage:stable

And so on.

In very large clusters, the schema of creating new tags for every revised image will eventually fill up the etcd datastore with excess tag metadata for images that are long outdated.