How-To: Deploy Python Flask applications using NGINX and uWSGI – Installation (Part 1 of 3)

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Image credit: Vecteezy, Python, uWSGI, NGINX and Ubuntu

You’ve written your first application in Python. And you want to try to see it available in publicly accessible, what do you want to do next? That’s right you want it deployed. This can be done on a Ubuntu 22.04 machine.

To create a simple Web/Flask Python application and deploy it on an NGINX server with uWSGI and uWSGI Emperor. This is a 3-part guide. This part covers the Installation of the required packages. It will install the following

  • NGINX
  • uWSGI
  • uWSGI-Emperor
  • Flask

It will also cover creation of

  • Virtual Environment
  • Installation of python packages via the requirements.txt

Prerequisites

  • Ubuntu 22.04
  • Python 3.x has been installed. For instructions see here.

Verification

01. Verify that Python and Pip3 has been installed

$ python -V 
# or
$ python3 -V

$ pip -V
# or
$ pip3 -V

Output:

Python 3.10.6

Install Pip and Virtual environment if not yet installed. Execute the following.

$ sudo apt-get install python3-pip -y
$ sudo apt-get install python3-venv -y

Setup the Python Virtual Environment

01. Create the python virtual environment. In this example we are creating the environment in the user’s home directory. But you can change its location depending on your preference and standards

$ cd ~/
$ python3 -m venv geek-venv

02. Move to the virtual environment directory

$ cd geek-venv/bin

03. Under the /bin directory activate the virtual environment using the source command. This will activate the virtual environment

$ source activate

04. Once the virtual environment is activated, use pip command to install the python packages required by your app.

(geek-venv) geek@box:~/geek-venv/bin$ pip install --upgrade pip

05. To deactivate the virtual environment.

(geek-venv) geek@box:~/python3-venv/bin$ deactivate

uWSGI Installation

01. Install the uwsgi.

$ sudo apt-get update

// Minimal Install (Recommended for Production Environment)
$ sudo apt-get install uwsgi uwsgi-plugin-python3 -y
  
// Complete Install (Generally used for Development Environment)
$ sudo apt-get install uwsgi uwsgi-extra uwsgi-plugins-all uwsgi-plugin-python3 -y

If the build-essential package is not installed, install it using the following command.

$ sudo apt-get install build-essential -y

02. Check and verify the installation

$ uwsgi --version

Output:

2.0.20-debian

Note: The packages uwsgi-extra and uwsgi-plugins-all are optional packages that ensures that all uwsgi packages are needed during development and might not be needed during production deployments.

03. Install the uwsgi emperor.

Note: Normally, uwsgi is enough for running single app deployment, but we use emperor mode for running single and multi-app deployments. It is a special uWSGI instance that will monitor specific events and will spawn/stop/reload instances on demand.

$ sudo apt-get install uwsgi-emperor -y

uWSGI Directories

Below are the uWSGI directories you have to be wary of, as some of them are the ones you will be troubleshooting if there are any problems.

# uWSGI file system

    ## Default root configuration
      /usr/share/uwsgi/conf/default.ini

    ## Configuration location for applications
      /etc/uwsgi/apps-available
      /etc/uwsgi/apps-enabled

# uWSGI (Emperor) file system

    ## Default root configuration
      /etc/uwsgi-emperor/emperor.ini
    
    ## Configuration location for applications
      /etc/uwsgi-emperor/vassals

    ## Logs
      /var/log/uwsgi/emperor.log

    ## Socket
      /var/run/

Nginx Installation

01. Install the nginx.

# Minimal Install (Recommended for Production Environment)
$ sudo apt-get install nginx nginx-extras

# Complete Install (Generally used For Development Environment)
$ sudo apt-get install nginx-full

02. Verify if NGINX is installed

$ nginx -V

It should show the NGINX version. Sample is below:

nginx version: nginx/1.18.0 (Ubuntu)
built with OpenSSL 3.0.2 15 Mar 2022
TLS SNI support enabled
configure arguments: –with-cc-opt=’-g -O
…

03. To test if nginx is working. 

$ curl http://localhost

It should show the NGINX page.

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href=”http://nginx.org/”>nginx.org</a>.<br/>
Commercial support is available at
<a href=”http://nginx.com/”>nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

04. Remove the default nginx configuration and restart the NGINX service. 

$ sudo rm /etc/nginx/sites-enabled/default
$ sudo service nginx restart

Execute the following.  

$ curl http://localhost

It will return an error that we will fix later.

curl: (7) Failed to connect to localhost port 80 after 0 ms: Connection refused

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