uWSGI

uWSGI

uWSGI is a fast, compiled server suite with extensive configuration and capabilities beyond a basic server.

It can be very performant due to being a compiled program.
It is complex to configure beyond the basic application, and has so many options that it can be difficult for beginners to understand.
It does not support Windows (but does run on WSL).
It requires a compiler to install in some cases.

This page outlines the basics of running uWSGI. Be sure to read its documentation to understand what features are available.

Installing

uWSGI has multiple ways to install it. The most straightforward is to install the pyuwsgi package, which provides precompiled wheels for common platforms. However, it does not provide SSL support, which can be provided with a reverse proxy instead.

Create a virtualenv, install your application, then install pyuwsgi.

$ cd hello-app
$ python -m venv .venv
$ . .venv/bin/activate
$ pip install .  # install your application
$ pip install pyuwsgi

If you have a compiler available, you can install the uwsgi package instead. Or install the pyuwsgi package from sdist instead of wheel. Either method will include SSL support.

$ pip install uwsgi
# or
$ pip install --no-binary pyuwsgi pyuwsgi

Running

The most basic way to run uWSGI is to tell it to start an HTTP server and import your application.

$ uwsgi --http 127.0.0.1:8000 --master -p 4 -w hello:app
*** Starting uWSGI 2.0.20 (64bit) on [x] ***
*** Operational MODE: preforking ***
mounting hello:app on /
spawned uWSGI master process (pid: x)
spawned uWSGI worker 1 (pid: x, cores: 1)
spawned uWSGI worker 2 (pid: x, cores: 1)
spawned uWSGI worker 3 (pid: x, cores: 1)
spawned uWSGI worker 4 (pid: x, cores: 1)
spawned uWSGI http 1 (pid: x)

If you’re using the app factory pattern, you’ll need to create a small Python file to create the app, then point uWSGI at that.

wsgi.py

from hello import create_app
app = create_app()

$ uwsgi --http 127.0.0.1:8000 --master -p 4 -w wsgi:app

The --http option starts an HTTP server at 127.0.0.1 port 8000. The --master option specifies the standard worker manager. The -p option starts 4 worker processes; a starting value could be CPU * 2. The -w option tells uWSGI how to import your application

Binding Externally

uWSGI should not be run as root with the configuration shown in this doc because it would cause your application code to run as root, which is not secure. However, this means it will not be possible to bind to port 80 or 443. Instead, a reverse proxy such as nginx or Apache httpd should be used in front of uWSGI. It is possible to run uWSGI as root securely, but that is beyond the scope of this doc.

uWSGI has optimized integration with Nginx uWSGI and Apache mod_proxy_uwsgi, and possibly other servers, instead of using a standard HTTP proxy. That configuration is beyond the scope of this doc, see the links for more information.

You can bind to all external IPs on a non-privileged port using the --http 0.0.0.0:8000 option. Don’t do this when using a reverse proxy setup, otherwise it will be possible to bypass the proxy.

$ uwsgi --http 0.0.0.0:8000 --master -p 4 -w wsgi:app

0.0.0.0 is not a valid address to navigate to, you’d use a specific IP address in your browser.

Async with gevent

The default sync worker is appropriate for many use cases. If you need asynchronous support, uWSGI provides a gevent worker. This is not the same as Python’s async/await, or the ASGI server spec. You must actually use gevent in your own code to see any benefit to using the worker.

When using gevent, greenlet>=1.0 is required, otherwise context locals such as request will not work as expected. When using PyPy, PyPy>=7.3.7 is required.

$ uwsgi --http 127.0.0.1:8000 --master --gevent 100 -w wsgi:app
*** Starting uWSGI 2.0.20 (64bit) on [x] ***
*** Operational MODE: async ***
mounting hello:app on /
spawned uWSGI master process (pid: x)
spawned uWSGI worker 1 (pid: x, cores: 100)
spawned uWSGI http 1 (pid: x)
*** running gevent loop engine [addr:x] ***