I am running Nginx as a reverse proxy in front of a Python (Gunicorn) application server.
I would like to configure it such that reading from a (potentially large) client request is aborted and the connection with the downstream client is closed once the upstream server has sent a response and closed its connection.
Ideally, the upstream response is still sent downstream to the client before closing the connection.
The use-case is summarized as follows:
* requests may be relatively large; processing them in nginx (including SSL) is expensive and a performance-bottleneck.
* it is often possible to determine that a request is invalid based on a small percentage of leading bytes of the request (i.e. request-headers, or other header information)
* the logic for determining this fact is in the upstream application server and is non-trivial and dynamic in nature, i.e. pushing the logic into an nginx conf is undesirable.
The implementation of the part that I got working is:
* In my Python application code, I do reading from the request in streaming style. I return a (non-streaming, but small) response when having determined one of the error conditions.
* Gunicorn (configured with the "sync" worker) writes the response to the socket and closes the connection. (i.e. sock.close)
My test set up is to have an artificially rate-limited client (basically putting sock.send(single_byte) in a loop with a sleep).
* Running Gunicorn without nginx in front, I see that the client indeed stops sending right after Gunicorn closes the connection
* Running Gunicorn with ngnix in front, I see (having added a print-statement) that Gunicorn closes its connection (with Nginx). But Nginx does not take that as a clue to drop the connection with the client.
The relevant part of the Nginx conf is:
```
location / {
# Pass the request to Gunicorn via proxy_pass.
proxy_pass http://127.0.0.1:8000;
proxy_request_buffering off; # this is needed such that the upstream server can read the parts of the request that have been sent by the test script and act on it.
proxy_buffering off; # as I understand it this is not needed / helpful, but I added it "just in case"
```
How do I instruct nginx to pass on the upstream connection-close on to the client?
Previously on (the version on the present forum is more up-to-date): https://serverfault.com/questions/1162301/configure-nginx-to-close-connection-when-upstream-has-sent-its-response
