[BuildStream] Artifact cache authentication/metrics

[Adam Jones <adam jones codethink co uk>]

Hi All,

I was speaking with Edmund about configuring the buildstream cache and
he raised some interesting questions about how well equipped the cache
is for shared instances.

The idea being that in the future people may want to share a cache
between multiple projects/teams (at scale), but this would pose
multiple problems:

A) How will these different entities access the cache server?
B) Can custom authentication methods be implemented? 
C) Can the access rates be tracked and logged for each user?

I explained that the docs does mention the use of a reverse-proxy for
authentication, but this does not get any further elaboration:
"Alternatively, you can set up a reverse proxy and handle
authentication and authorization there."

And that currently to push the server you have to maintain a list of
authorized certificates, under authorized.crt. But apart from that i am
not sure how granular you can be.

So he asked me to raise these points in order to try and get some
further information, i was originally going to raise an issue, but
though maybe the ML is a better approach for this type of question.

Many thanks,

Adam Jones