UWSGI block incoming connections when all threads are busy

I have a simple UWSGI app put behind a LB with the following .ini config

[uwsgi]
socket=0.0.0.0:5071
chdir = src/
wsgi-file = uwsgi.py
processes=2
threads=1
protocol=http
plugins=python
exit-on-reload=false
master=true
# Cleanup of temp files
vacuum = true    

When all 2x1 threads are busy, the application keeps serving incoming connections by queueing them, waiting for a thread to free.

This is somehow an unwanted behavior in my case, as I would like UWSGI to return a 5xx status code which will allow me to not oversaturate the resources of a single distribution.

Client testing code

Attaching the test client code for the UWSGI application

proxy = {
    'http':'http://localhost:5071'
}

@threaded
def f():
    print('Sending request')
    response = requests.get('http://dummy.site',proxies=proxy)
    print(str(response.status_code )+ response.text)

for i in range(5):
    f()

Test (1)

Adding listen = 2 to .ini and firing 3 requests simultaneously would just print:

*** uWSGI listen queue of socket "0.0.0.0:5071" (fd: 3) full !!! (3/2) ***

while the third connection seems to still be somehow accepted, queued and later executed instead of a 5xx error being thrown.

Test (2)

Adding listen = 0 to .ini and firing 5 requests simultaneously would just execute two requests at a time. The full queue output is not showing anymore. Somehow, the requests are somewhere still queued and executed when threads get freed.

How can I block incoming connections to the UWSGI application when all threads are busy?

This is a truly bizarre request, but if you really want to do this, you can try reducing the listen queue (to zero), i.e. --listen 0. I haven't tested this and don't know if zero is even considered a valid value. This is something that is normally increased as a site gains traffic, not decreased.