Flask with uWSGI + Nginx

This tutorial shows you to set up a simple Flask app with uWSGI + Nginx.

At the end of this tutorial, you will be able to do the following:

• Start or stop the app using Upstart
• Visit the app at http://flask-uwsgi.ubuntu.local. (Throughout this tutorial, replace ubuntu.local with your machine's name.)

Setting up the Python environment

First, install the following packages.

sudo apt-get install build-essential python-dev python-pip

build-essential and python-dev are used to compile C extensions. Pip is used to install system commands.

Next, install the following Pip packages.

sudo pip install virtualenv uwsgi

Next, create the Virtualenv for this tutorial.

cd flask-uwsgi
virtualenv env
source env/bin/activate
pip install flask

Next, run the Flask app using uWSGI.

uwsgi --http 0.0.0.0:8080 --home env --wsgi-file flask_uwsgi.py --callable app --master

You should be able to visit http://ubuntu.local:8080.

Creating an Upstart service for uWSGI

First, set up the directories the service will use.

# Create a directory for the UNIX sockets
sudo mkdir /var/run/flask-uwsgi
sudo chown www-data:www-data /var/run/flask-uwsgi

# Create a directory for the logs
sudo mkdir /var/log/flask-uwsgi
sudo chown www-data:www-data /var/log/flask-uwsgi

# Create a directory for the configs
sudo mkdir /etc/flask-uwsgi

Next, create the init script.

• Copy the init script template to /etc/init/flask-uwsgi.conf.
• Replace /path/to/flask-uwsgi with the path to this directory.

Next, create the config file.

• Copy the config template to /etc/flask-uwsgi/flask-uwsgi.ini.
• Set uid and gid to the numeric uid and gid for www-data.

Next, start uWSGI.

sudo service flask-uwsgi start

Next, check that uWSGI is running.

sudo less /var/log/flask-uwsgi/flask-uwsgi.log

You should see messages from uWSGI.

Connecting uWSGI to Nginx

First, install Nginx (if you haven't already).

sudo apt-get install nginx

Next, create the Nginx config.

• Copy the config template to /etc/nginx/sites-available/flask-uwsgi.
• Replace ubuntu.local with your machine's name.

Next, enable the config.

sudo ln -sf /etc/nginx/sites-available/flask-uwsgi /etc/nginx/sites-enabled
sudo service nginx reload

Next, check that the app is reachable through Nginx. You should be able to visit http://flask-uwsgi.ubuntu.local.

Congratulations! You have deployed an app to uWSGI + Nginx.

Code reloading

You can reload code (or reload the uWSGI config) by sending the HUP signal to uWSGI.

sudo service flask-uwsgi reload

Adding or simulating DNS entries

If you are running this tutorial in a VM, you can simulate DNS names in the host by editing /etc/hosts. This allows you to visit your VM from your host's browser.

# Replace <IP> with your VM's IP.
<IP> ubuntu.local flask-uwsgi.ubuntu.local

To check this, visit http://ubuntu.local (or http://flask-uwsgi.ubuntu.local) in your host's browser.

References

• uWSGI Quickstart
• uWSGI Configuration
• uWSGI Upstart