Apache cache/proxy module

Looking for a custom apache module to act as both a reverse proxy and local (*disk or memory*) cache. Very similar to both mod_cache and mod_proxy except the proxy needs to only open one connection to the origin server no matter how many clients connect requesting the same file. Until the front end server (running the module) gets the entire file, all clients should be served from what it has already downloaded. ***e.g.*** A client requests [login to view URL] (*a 800 meg file*) and its not in the local cache. The proxy server opens a connection to the backend (*which could be over the internet*) and starts downloading [login to view URL] and doing a pass through to the client - it should not wait for the entire file to be downloaded into cache and should not pass the client through to the origin directly. If client #2 requests the same file before the proxy server has downloaded it, it should server the partial file it has and keep the connection open until its served the complete file sending more data as it gets it from the origin server. The module should be able to handle hundreds of file requests with hundreds of ‘concurrent’ connections for each file request.