WSGI server setup

Run a WSGI server and expose your Flask app with a URL endpoint

Step 1: Install WSGI server

First, we need to install our WSGI server on our Debian machine:

pip3 install gunicorn
    

You will need to install your wsgi server in our python venv too but that is later.

Step 2: Create a systemd service

Next, we create a systemd service so our gunicorn server starts on boot.

vim /etc/systemd/system/loquax.service

[Unit]
Description=Gunicorn instance to serve Loquax
After=network.target

[Service]
User=root
Group=root

# Sets the working directory for the Gunicorn process.
WorkingDirectory=/var/www/loquax

# Sets the PATH environment variable so it includes the directory
# where the Python virtual environment is located.
Environment="PATH=/var/www/loquax/venv/bin"

# The command to start the Gunicorn server with 3 worker processes,
# binding to all network interfaces on port 8000
ExecStart=/var/www/loquax/venv/bin/gunicorn --workers 3 \
--bind 0.0.0.0:8000 app:app

[Install]
WantedBy=multi-user.target
    

Step 3: Configure Nginx

Now you want nginx or your webserver to bind to the same port as your wsgi server w/ URL prefix. Add the below "loquax" block to your nginx "server" block:

vim /etc/nginx/sites-available/mywebsite

server {
        server_name nargothrond.xyz ;
        root /var/www/mysite ;
        index index.html index.htm index.nginx-debian.html ;
        client_max_body_size 64M;
        location / {
                try_files $uri $uri/ =404 ;
        }
    proxy_set_header X-Forwarded-For $remote_addr;

 #...
        location /loquax/ {
        include proxy_params;
        proxy_pass http://localhost:8000/;
    }
 #...
}
      

Start up your wsgi server

systemctl daemon-reload
systemctl enable loquax
systemctl start loquax
      

Or to start debugging your WSGI server:

systemctl status loquax
systemctl restart loquax
    

Step 4: Run your app

Ensure your app.py, index.html and all the things your Flask app will link in are in the same path specified in your "Step 2" systemd service, i.e:

ls -l /var/www/loquax

-rw-r--r-- 1 root root  764 Jul  5 07:09 app.py
drwxr-xr-x 2 root root 4096 Jul  5 07:09 __pycache__
-rw-r--r-- 1 root root   21 Jul  5 07:09 requirements.txt
drwxr-xr-x 2 root root 4096 Jun 27 21:00 static
drwxr-xr-x 2 root root 4096 Jun 27 21:00 templates
drwxr-xr-x 5 root root 4096 Jul  5 04:43 venv
    

Don't forget to reactivate your virtual env if you update some packages your flask app relies on.

# Define the remote path to the project
REMOTE_PATH="/var/www/loquax"
VENV_PATH="${REMOTE_PATH}/venv"

# Check if the venv exists, if not create it
if [ ! -d \"${VENV_PATH}\" ]; then
    python3.10 -m venv ${VENV_PATH} \
    || echo 'Failed to create virtual environment' ;
else
    echo 'Virtual environment already exists' ;
fi ;

# Activate the virtual environment
source ${VENV_PATH}/bin/activate ;