Question

Flask+nginx+uwsgi+Ubuntu tutorial

Posted on May 3, 2017
Nginx Ubuntu 16.04
Asked by broodforge

My hopes are lost and so is my temper. I have followed the tutorial found here - https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-uwsgi-and-nginx-on-ubuntu-16-04

I have reinstalled and started all over 10 times and still same PROBLEM. Is there another tutorial available because this only works to 80%. All works fine up to a certain point but I always get a 502 gateway problem.

I created a new user belonging to sudo group. Ssh:ed to server with this new user – all good. Set up domain also and if I ping domainname.com the correct droplet ip gives reply – all good.

python myproject.py (to start flask) works perfect

uwsgi --socket 0.0.0.0:5000 --protocol=http -w wsgi:app

Works perfect and site is accessible with IP http://server_IP:5000

Content of wsgi.py-

from myproject import app

if name == “_main”: app.run()

Content of myproject.ini looks like -

[uwsgi]

module = wsgi:app

master = true processes = 5

socket = myproject.sock chmod-socket = 660 vacuum = true

die-on-term = true

Content of /etc/systemd/system/myproject.service:

[Unit] Description=uWSGI instance to serve myproject After=network.target

[Service] User = blizzard Group = www-data WorkingDirectory = /home/blizzard/myproject Environment = “PATH=/home/blizzard/myproject/myprojectenv/bin” #IS THIS LINE WRONG?? ExecStart=/home/blizzard/myprojectenv/bin/uwsgi --ini myproject.ini

[Install] WantedBy = multi-user.target

Content of /etc/nginx/available-sites/myproject

server { listen 80; server_name billigaflygtilllondon.com www.billigaflygtilllondon.com;

    location / {
    include uwsgi_params;
    uwsgi_pass unix:///home/blizzard/myproject/myproject.sock;
    }

}

If this tutorial is wrong why dont staff delete it or at least the author updates it since I am not the ONLY ONE having problems. If there is a helpful soul who could guide me I would be more than happy.

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Jonathan Tittle • May 3, 2017

Accepted Answer

@broodforge

Here’s what I did, step-by-step, on a test Droplet with Ubuntu 16.04 64bit.

Update, Upgrade, Install

apt-get update \
&& apt-get -y dist-upgrade \
&& apt-get -y install python3-pip python3-dev nginx \
&& pip3 install virtualenv

Create New User + Directories

mkdir -p /home/sammy/myproject \
&& useradd -d /home/sammy sammy

Setup VirtualEnv

cd /home/sammy/myproject \
&& virtualenv myprojectenv

Source Env File

source /home/sammy/myproject/myprojectenv/bin/activate

Install Flask and UWSGI

pip install uwsgi flask

Create Project File

nano /home/sammy/myproject/myproject.py

Within it, I pasted:

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "<h1 style='color:blue'>Hello There!</h1>"

if __name__ == "__main__":
    app.run(host='0.0.0.0')

Testing myproject.py

python myproject.py

I see the Hello There as I should, so let’s move on…

Create the WSGI Entry Point

nano /home/sammy/myproject/wsgi.py

Within it, I pasted:

from myproject import app

if __name__ == "__main__":
    app.run()

Testing UWSGI

uwsgi --socket 0.0.0.0:5000 --protocol=http -w wsgi:app

I see the Hello Three as I should, so let’s move on.

Deactivate

deactivate

Creating a uWSGI Configuration File

nano /home/sammy/myproject/myproject.ini

Within it, I pasted:

[uwsgi]
module = wsgi:app

master = true
processes = 5

socket = myproject.sock
chmod-socket = 660
vacuum = true

die-on-term = true

Creating systemd Service File

nano /etc/systemd/system/myproject.service

Within it, I pasted:

[Unit]
Description=uWSGI instance to serve myproject
After=network.target

[Service]
User=sammy
Group=www-data
WorkingDirectory=/home/sammy/myproject
Environment="PATH=/home/sammy/myproject/myprojectenv/bin"
ExecStart=/home/sammy/myproject/myprojectenv/bin/uwsgi --ini myproject.ini

[Install]
WantedBy=multi-user.target

Setting Proper Permissions

Add sammy to www-data group:

usermod -aG www-data sammy

chown -R sammy:www-data /home/sammy/*

Starting and Enabling the Service

systemctl start myproject

systemctl enable myproject

Setting Up NGINX

nano /etc/nginx/sites-available/myproject

Within it, I pasted:

server {
    listen 80;
    server_name MY_DROPLET_IP;

    location / {
        include uwsgi_params;
        uwsgi_pass unix:///home/sammy/myproject/myproject.sock;
    }
}

Created a symlink using:

ln -s /etc/nginx/sites-available/myproject /etc/nginx/sites-enabled

Restart NGINX:

systemctl restart nginx

…

For this particular setup, passing --uid and --gid isn’t required and systemctl does handle the user and group permissions correctly.

sfox9 • May 18, 2019

I just want to Thank You for this post and to all who helped solve these issues. It really helped me out BIG TIME. I like you was stuck and very frustrated, but this thread was a godsend.

Jonathan Tittle • May 4, 2017

@broodforge

Starting a new reply as the other was at its max.

You could very well use the same user and group, though from a security standpoint, it’s not the best method. Ideally, each project should run as an individual user (that isn’t root or a sudo user).