Async worker on gunicorn seems blocking

Question

I am using a Flask app with the gunicorn server and the gevent worker class, which according to the gunicorn documentation is an asynchronous worker. However, when I launch gunicorn with a single worker and try to make a long request (I added sleep(10) in the route function, but in reality this also happens when processing large uploads), I can't make any request until the previous one is finished. It behaves as is it is a synchronous worker, one request at a time.

Is this the normal behavior? Am I missing something about synchronous vs asynchronous workers?

Answer 1

If you don't monkey-patch sleep (or use gevent's non-blocking version of sleep) then a worker that blocks blocks the entire event loop.

Either call gevent.monkey.patch_all (or more specifically gevent.monkey.patch_time) or replace your call to time.sleep with gevent.sleep