Deploy Flask Application

Introduction

In this lab, we will learn how to deploy a Flask application to a server. We will create a distribution file for our application and install it on the server. The lab assumes you have a basic understanding of Flask, Python's virtual environments, and the command line.

Note: You need to create the code file yourself and run it in the environment. You can preview the Flask service status on Web 5000.

Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL flask(("`Flask`")) -.-> flask/CoreConceptsGroup(["`Core Concepts`"]) flask(("`Flask`")) -.-> flask/DataHandlingGroup(["`Data Handling`"]) flask(("`Flask`")) -.-> flask/DevelopmentToolsGroup(["`Development Tools`"]) flask/CoreConceptsGroup -.-> flask/application_object("`Application Object`") flask/DataHandlingGroup -.-> flask/incoming_request_data("`Incoming Request Data`") flask/DataHandlingGroup -.-> flask/response_objects("`Response Objects`") flask/CoreConceptsGroup -.-> flask/sessions("`Sessions`") flask/CoreConceptsGroup -.-> flask/json_support("`JSON Support`") flask/CoreConceptsGroup -.-> flask/useful_internals("`Useful Internals`") flask/DevelopmentToolsGroup -.-> flask/command_line_interface("`Command Line Interface`") subgraph Lab Skills flask/application_object -.-> lab-136343{{"`Deploy Flask Application`"}} flask/incoming_request_data -.-> lab-136343{{"`Deploy Flask Application`"}} flask/response_objects -.-> lab-136343{{"`Deploy Flask Application`"}} flask/sessions -.-> lab-136343{{"`Deploy Flask Application`"}} flask/json_support -.-> lab-136343{{"`Deploy Flask Application`"}} flask/useful_internals -.-> lab-136343{{"`Deploy Flask Application`"}} flask/command_line_interface -.-> lab-136343{{"`Deploy Flask Application`"}} end

Build the Application

First, we need to create a wheel file for our application. We will use the build tool for this. Install the build tool using pip if you haven't already:

## Install the build tool
pip install build

Now, use the build tool to create the wheel file:

## Build the wheel file
python -m build --wheel

The wheel file should be in the dist directory with a name like flaskr-1.0.0-py3-none-any.whl.

Install the Application on the Server

Copy the wheel file to your server. Once it's there, set up a new Python virtual environment and install the wheel file using pip:

## Install the wheel file
pip install flaskr-1.0.0-py3-none-any.whl

Since this is a new environment, you need to initialize the database again:

## Initialize the database
flask --app flaskr init-db

Configure the Secret Key

In a production environment, you should change the secret key to a random value. To generate a random secret key, run the following command:

## Generate a random secret key
python -c 'import secrets; print(secrets.token_hex())'

Create a config.py file in the instance folder and set SECRET_KEY to the generated value.

## .venv/var/flaskr-instance/config.py

SECRET_KEY = 'your_generated_secret_key'

Run the Application with a Production Server

For a production environment, you should use a WSGI server instead of the built-in development server. We will use Waitress as our WSGI server.

First, install Waitress:

## Install Waitress
pip install waitress

Now, tell Waitress to serve your application:

## Run the application with Waitress
waitress-serve --call 'flaskr:create_app'

Summary

In this lab, we learned how to deploy a Flask application to a production server. We built our application into a wheel file, installed it on the server, configured the secret key, and ran the application with a production WSGI server.