Running a Python Flask Server on a Serverless Container

caasnodejsPythonFlask

Reviewed on June 25, 2024

Flask is a Python framework that enables you to easily deploy simple web servers and APIs. In this tutorial, you will learn how to configure your Flask application to run on a Serverless Container.

Before you start

To complete the actions presented below, you must have:

• A Scaleway account logged into the console
• Owner status or IAM permissions allowing you to perform actions in the intended Organization
• A Serverless Containers namespace
• Installed Python 3, pip, and Docker on your computer

Creating a Flask application

We first need to create a simple Web Server with Python and the Flask framework.

1. Create a new folder for the project:
   mkdir my_python_project

2. Use your favorite text editor to create a requirements.txt. In this tutorial, we use nano:
   nano requirements.txt

3. Enter the following text in the requirements.txt file to define the library you want to import. Then save and quit the text editor:
   Flask==2.2.1

4. Create a server.py text file, and add the following code to it. This creates a simple web app using Flask:
   from flask import Flask
   import os
   import json
   
   DEFAULT_PORT = "8080"
   MESSAGE = "Hello, World from Scaleway Container!"
   
   app = Flask(__name__)
   
   @app.route("/")
   def root():
       return json.dumps({
           "message": MESSAGE
       })
   
   if __name__ == "__main__":
       # Scaleway's system will inject a PORT environment variable on which your application should start the server.
       port_env =  os.getenv("PORT", DEFAULT_PORT)
       port = int(port_env)
       app.run(debug=True, host="0.0.0.0", port=port)

Configuring your Docker image

To Dockerize our simple web app, we will use the official Python 3 Alpine image which is the smallest source image.

1. Create a Dockerfile using the following command:

   touch Dockerfile

   Tip

   A Dockerfile is a document that contains all the commands a user could call from the command line to create the image.

2. In the Dockerfile, add the following:

   • Define the Python base image you want to use:
   FROM python:3-alpine

   • Create a directory to store your application code:
   # Create app directory
   WORKDIR /usr/src/app

   • Install the required python libraries (defined in the requirements.txt file):
   COPY requirements.txt .
   RUN pip install -qr requirements.txt

   • Copy your application server code inside the Docker image:
   COPY server.py .

   • Define the PORT environment variable and expose port 8080. This dictates the port the application will bind to:
   ENV PORT 8080
   EXPOSE 8080

   • Use CMD to run the python command that will start your application:
   CMD [ "python3", "./server.py" ]

   Your final Dockerfile should look like this:

   FROM python:3.9-alpine
   
   # Create app directory
   WORKDIR /usr/src/app
   
   # Expose Ports
   ENV PORT 8080
   EXPOSE 8080
   
   # Install libraries
   COPY requirements.txt .
   RUN pip install -qr requirements.txt
   COPY server.py .
   
   CMD ["python3", "./server.py"]

Deploying the application on Serverless Containers

1. Build your image using the following command:
   docker build . -t <your application name>

2. Push the created image into the container registry linked to your Containers namespace
   Tip

   The registry name starts with funcscw + the namespace name.

3. Deploy the image using the Scaleway console.