Flask nginx gunicorn Raspberry Pi

flask_nginx_gunicorn.md

Python Flask + nginx + gunicorn

Setting up a python flask web application using nginx, gunicorn and systemd on a Rasperry Pi

In the following, we assume a working Flask application with the name of SCRIPT_NAME. First we need to install a couple of things:

sudo apt-get update && sudo apt-get upgrade

Installing nginx will fail if apache is running. If your installation breaks half ways, then remove the fragments, stop apache (and I actually suggest removing it in case not needed) and then install nginx again:

sudo apt-get remove nginx* --purge
sudo /etc/init.d/apache2 stop
sudo apt-get remove apache* --purge
sudo apt-get install nginx-common
sudo apt-get install nginx

then install the rest:

sudo pip3.4 install flask-bootstrap wtforms gunicorn

create a file /etc/nginx/sites-enabled/SCRIPT_NAME.conf with this content:

server {
        listen   8000; ## listen for port 8000
        location / {
        include proxy_params;
        proxy_pass http://unix:/home/pi/git/SCRIPT_NAME/SCRIPT_NAME_socket.sock;
    }
}

If you choose to use port 80, then you might notice in the same directory there is a file called default which is a sim link from the sites-available directory. If you don't remove it, it will still show the defaul web page of apache under /var/www even if you have removed apache completely. More info on this SO post.

Now restart nginx server:

sudo service nginx restart

now create a service in /etc/systemd/system/SCRIPT_NAME.service with the content:

[Unit]
Description=Unicorn Daemon for SCRIPT_NAME
After=network.target

[Service]
User=pi
Group=www-data
WorkingDirectory=/home/pi/git/SCRIPT_NAME
ExecStart=/usr/local/bin/gunicorn --workers 1 --bind unix:/home/pi/git/SCRIPT_NAME/SCRIPT_NAME_socket.sock controller:app

ExecReload=/bin/kill -s HUP $MAINPID
ExecStop=/bin/kill -s TERM $MAINPID


[Install]
WantedBy=multi-user.target

now run:

sudo systemctl daemon-reload && sudo systemctl enable SCRIPT_NAME

now you can start / stop the daemon like any other service.

sudo service SCRIPT_NAME start
sudo service SCRIPT_NAME stop

have fun!

p.s. at some point it might be beneficial to have a virtual_env for your python environment.

Many thanks goes to this tutorial: Hosting flask on linux with gunicorn and nginx.