gevent VS gunicorn

A sub-question for the folks here: is anyone using the combination of gevent and PyPy for a production application? Or, more generally, other libraries that do deep monkey-patching across the Python standard library?

Things like https://github.com/gevent/gevent/issues/676 and the fix at https://github.com/gevent/gevent/commit/f466ec51ea74755c5bee... indicate to me that there are subtleties on how PyPy's memory management interacts with low-level tweaks like gevent that have relied on often-implicit historical assumptions about memory management timing.

Not sure if this is limited to gevent, either - other libraries like Sentry, NewRelic, and OpenTelemetry also have low-level monkey-patched hooks, and it's unclear whether they're low-level enough that they might run into similar issues.

For a stack without any monkey-patching I'd be overjoyed to use PyPy - but between gevent and these monitoring tools, practically every project needs at least some monkey-patching, and I think that there's a lack of clarity on how battle-tested PyPy is with tools like these.

I'm not sure how much it replicates the CSP model, but the closest thing I've found to Go-style concurrency in Python is gevent: https://github.com/gevent/gevent

I personally still prefer to use it in all my projects.

Greenlet seems to have some troubles compiling with Python 3.9. https://github.com/gevent/gevent/issues/1627

I'm hoping so – gunicorn has a long-open pull request that would fix `--reuse-port`, which currently does nothing

https://github.com/benoitc/gunicorn/pull/2938

However, I'm curious about the best way to deploy, specifically with regard to WSGI. I've tried using the raw eventlet WSGI server (`eventlet.wsgi.server(eventlet.listen(("", 8000)), application)`). I then start it with `python manage.py runserver`. This has worked okay, but I'm unsure about how scalable it is. It seems like the standard stack is Django + Gunicorn + NGINX. Based on `python-socketio` documentation, this should be possible. I tried django + eventlet + gunicorn, but it seems like gunicorn a) [doesn't play nice with eventlet](https://github.com/benoitc/gunicorn/pull/2581) and b) only supports one worker. Gevent + Gunicorn doesn't have this bug, but still only supports one worker. Also, I'm not sure how actively maintained gevent is. So I'm not sure how scalable either Gunicorn + eventlet or Gunicorn + geventlet is as a WSGI server. So I'm not sure if Gunicorn is my best bet, or if it's too limited.

For building your API, I recommend using the Flask library. It is very beginner-friendly, and you will be able to build a simple API in a matter of minutes! Keep in mind that, for a more serious project, you should definitely use something like gunicorn to run you API as a production server.

Interesting looks like it might actually be a python bug. Somehow just changing from sys.exit(0) -> os._exit(0) apparently fixes it.

https://github.com/benoitc/gunicorn/pull/2820

The cool thing is that you can easily migrate your WSGI- application such as Flask, Django, or Gunicorn to AWS.

Yeah, that's kind of the impression I was getting. I stumbled across a github issue for gunicorn along these lines.

Taking a glimpse at gunicorn's code it looks like they pretty much all do the same: 2. seems to be creating a wsgi app using django's internals, and 3. uses 2.