I have an api with publishers + subscribers and I want to stop a publisher from uploading a lot of data if there are no subscribers. In an effort to avoid another RTT I want to parse the HTTP header, see if there are any subscribers and if not return an HTTP error before the publisher finishes sending all of the data. 
Is this possible? If so, how do I achieve it. I do not have post-buffering enabled in uwsgi and the data is being uploaded with a transfer encoding of chunked. Therefore, since uWSGi is giving me a content-length header, it must have buffered the whole thing somewhere previously. How do I get it to stop?
P.S. uWSGi is being sent the data via nginx. Is there some configuration that I need to set there too perhaps?
The limit here is nginx. It cannot avoid (unless when in websockets mode) buffering the input. You may have more luck with apache or the uWSGI http router (albeit i suppose they are not a viable choice)
Can uWSGI return a response before the POST data is uploaded?