Provide HTTP header with SHA sum of the content

Author: lzap@redhat.com (lzap@redhat.com)

Redmine Issue: 6578, https://pulp.plan.io/issues/6578

Hello,

Lukáš from Satellite engineering here. We struggle for many years with (re)downloading of initram and kernel from kickstart trees. We need to redownload them every provisioning to find if something changed (new Anconda). I tried to play around with HTTP ETag header but it looks like the best fit for our case (naming downloaded file in unique way) would be if Pulp (or Apache) could report file checksum via HTTP header (SHA or anything pretty much) or any kind of unique id that is associated with the contents.

This way we could do HTTP HEAD to get unique identifier of the kickstart files to:

1. See if the content has changed and it needs to be redownloaded.
2. Generate unique file name to store the files in the TFTP directory.

Is this something that could be implemented?

Start by tracing how Pulp serves the kickstart files and how HTTP HEAD responses are generated, using the existing ETag behavior as context. Determine how a content-derived SHA or equivalent identifier could be exposed in a response header. Done means clients can use HEAD to detect content changes and derive a unique stored filename.