I am working on a load balancing system where the upstream providers need to change at runtime. The available peer group will be routed either by a hash, or by round robin, but the size of the peer group might change between any request.

The easy way seems to be to bypass the upstream http functionality altogether and simply return the appropriate peer from the callback in r->upstream->peer.get

Will this work?
Does something else already do this?
If not, what is a more idiomatic way to write this module?