PYTHON FLASK WITH NGINX & UWSGI

CONTENTS

1. app Folder
2. uwsgi.ini
3. nginx_config
4. production_flask.service

USAGE

1. app Folder - It contains you complete app and directories. Do initialize it as a virtual environment and install requirements.txt included in that folder. (Hold on !!) We will be going through it in some time
2. uwsgi.ini - UWSGI server configuration. Edit/Replace the following places:
   • my_app_folder: Replace PROJECT_FOLDER_HERE With your Project app Path
   • my_user: Replace MY_USERNAME_HERE With your UserName; You can get your username using command whoami
3. nginx_config - Contains the main nginx configuration. Edit/Replace the following to make it work properly:
   • uwsgi_pass: Replace PROJECT_FOLDER_HERE With your Project Path
   • [OPTIONAL] listen: Port on which you want nginx to Listen
   • [OPTIONAL] server_name: Currently its 0.0.0.0 . You can change it as per your needs.
4. production_flask.service - A Systemd service file to ensure that the server restarts on failure and can be set to auto-start in case of server restart. Edit/Replace the following terms:
   • Replace USER_NAME_HERE with your user-name.
   • Replace PROJECT_FOLDER_HERE with your project app directory
   • Replace uwsgi.ini_PATH_HERE with uwsgi.ini path

PREREQUISITES

1. Clone this repository.

2. A Stable Debian based Linux O.S, preferrably Ubuntu with sudo privileges configured. I have tried it on Ubuntu 18.04 and it worked flawlessly.

3. We will me utilizing Virtual Env Wrapper for complete Flask Project.

4. Before proceeding any further, Install the following packages:

   sudo apt-get update
   sudo apt-get install python3 python3-pip
   sudo apt-get install systemd nginx
   sudo pip3 install virtualenv

5. Initializing Project Virtual Environment:

   cd PROJECT/APP_FOLDER
   virtualenv -p python3 venv
   source venv/bin/activate
   pip3 install -r requirements.txt

6. Now, as this project is configured with a simple Hello World Application inside app.py, we will be using it for deployment. You can also have your complete project inside the app folder with an app.py file

INSTALLATION INSTRUCTIONS

Now comes the main dreaded and & feared (kiddin!) Installation part. Considering you have installed all the above steps successfully, will start with Nginx.

1. You will need to place your nginx_config in /etc/nginx/sites-available/nginx_config. Then, to enable this nginx configuration, we will have to link it to the nginx sites-enabled directory using this command:

   sudo ln -s /etc/nginx/sites-available/nginx_config /etc/nginx/sites-enabled

   The above command will create a sym-link for nginx_config

2. Restart Nginx:

   sudo service nginx restart

3. Before starting up the main service, let make a folder for logs; the configuration for which is defined in uwsgi.ini

   sudo mkdir -p /var/log/uwsgi
   sudo chown -R thetechfreak:thetechfreak /var/log/uwsgi

   Instead of thetechfreak use your username.

4. Now, we will have to configure systemd service & for that we place production_flask.service in /etc/systemd/system/production_flask.service and then restart and enable the service to auto start after reboot.

   sudo systemctl start production_flask.service
   sudo systemctl enable production_flask.service

   At this point, our service should successfully start and incase of any updates you can just restart the service using:

   sudo systemctl restart production_flask.service

After this step, your server should be up and running

LOGGING & MONITORING

In order to check the logs, you can navigate to the logs directors /var/log/uwsgi/

Monitoring the service is also very easy as you justneed to go inside your PROJECT_DIR and run the following command:

uwsgitop stats.production_flask.sock

OR

If you want to monitor the logs of the application itself, you can make use of journalctl: Note: These logs are same as the one which are stared in /var/log/uwsgi/; So, unless you really want to have a real time log on your system, it's not required:

sudo journalctl -u production_flask.service -f

Serving Static Files Using Nginx

If your application requires static files to be served, you can add the following rule inside nginx_config file:

location /static {
    root APP_DIR;
}

Replace APP_DIR with your application directory and as a result, all your static files located at APP_DIR/static will be served by nginx

FINAL THOUGHTS

These are my final thoughts and some notes which are worth noting.

1. UWSGI is configured in lazy-apps mode which is responsible for loading the application one time per worker. You can read more about it here
2. Only Basic configuration of nginx is used; however it is sufficient for most of the use cases. But still, if you want to tune it further you can read up here
3. If your app requires some parameters to be passed, you can make use of CONFIGPARSERS but DO-NOT pass it via command line as uWSGI is the one responsible for invoking the app.
4. In this app, Socket permission is given to everyone. You can adjust it as per your needs, but make sure that nginx and uWSGI can still talk to each other
5. If something goes wrong, the first place to check is the log files. By default, nginx writes error message to the file /var/log/nginx/errors.log

Contributions are very welcome. Do make PULL requests if you want to change anything, or post an ISSUE if you encounter any bugs.