Deploying a Flask App

Flask is a lightweight and flexible Python web framework, known for its simplicity and minimalism. It is ideal for building small to medium-sized web applications and APIs, offering great extensibility and a large ecosystem of extensions.

This guide explains how to deploy a Flask application to Klutch.sh, both with and without a Dockerfile. It also covers installation and provides sample code to get started.

Prerequisites

• Python 3.8+
• pip installed
• Git and GitHub account
• Klutch.sh account

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Getting Started: Install Flask

1. Create a new directory for your app and set up a virtual environment:

   mkdir my-flask-app
   cd my-flask-app
   python3 -m venv venv
   source venv/bin/activate

2. Install Flask:

   pip install flask

3. Create a basic Flask app (app.py):

   from flask import Flask
   import os
   
   app = Flask(__name__)
   
   @app.route('/')
   def home():
       return "Hello from Flask on Klutch.sh!"
   
   if __name__ == '__main__':
       port = int(os.environ.get('PORT', 5000))
       app.run(host='0.0.0.0', port=port)

4. Add a requirements.txt file:

   pip freeze > requirements.txt

5. Test locally:

   python app.py

   Visit http://localhost:5000 to see your app running.

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Deploying Without a Dockerfile

1. Push your Flask app to a GitHub repository.
2. Log in to Klutch.sh.
3. Create a new project and give it a name.
4. Create a new app:
   • Select your Flask GitHub repository and branch
   • Set the port to route traffic (usually 5000 for Flask)
   • Choose region, compute, number of instances, and add any environment variables
5. Add a start command in your app settings:

   python app.py

6. Click “Create” to deploy. Klutch.sh will build and deploy your app automatically.

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Deploying With a Dockerfile

1. Add a Dockerfile to your project root. Example:

   # Use official Python image
   FROM python:3.11-slim
   
   # Set working directory
   WORKDIR /app
   
   # Copy requirements and install dependencies
   COPY requirements.txt ./
   RUN pip install --no-cache-dir -r requirements.txt
   
   # Copy app source
   COPY . .
   
   # Expose port (match your Flask app)
   EXPOSE 5000
   
   # Start the app
   CMD ["python", "app.py"]

2. Push your code (with Dockerfile) to GitHub.
3. In Klutch.sh, follow the same steps to create a project and app, but select the Dockerfile option when prompted.
4. Set the service details and environment variables as needed.
5. Click “Create” to deploy. Klutch.sh will build your Docker image and deploy your app.

Note: Your Flask app should always listen on the PORT environment variable as shown above.

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Resources

• Klutch.sh Documentation
• Flask Documentation

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Deploying to Klutch.sh is simple and flexible. Choose the method that best fits your workflow and project requirements.