How to Deploy a Flask Application on Google Cloud with Docker

Deploying web applications can sometimes feel like a daunting task, especially for newcomers. However, with the right tools and a systematic approach, you can easily deploy a Flask application on Google Cloud using Docker. This guide will walk you through the entire process, ensuring that you understand each step and have the necessary code snippets to get your application running smoothly.

What is Flask?

Flask is a lightweight web framework for Python that is designed for building web applications quickly and easily. Its simplicity and flexibility have made it a popular choice for developers who appreciate minimalism and the ability to scale their applications as needed.

What is Docker?

Docker is a platform that enables developers to automate the deployment of applications inside lightweight, portable containers. By using Docker, you can ensure that your application runs consistently regardless of the environment, making it an ideal choice for deploying applications in the cloud.

Why Use Google Cloud?

Google Cloud Platform (GCP) provides a robust environment for deploying applications with numerous services that can help you scale, secure, and manage your applications. It offers features like load balancing, automatic scaling, and cloud storage, making it an excellent choice for deploying Flask applications.

Prerequisites

Before we dive into the deployment process, ensure that you have the following prerequisites:

• A Google Cloud account
• Basic knowledge of Python and Flask
• Docker installed on your local machine
• Google Cloud SDK installed

Step 1: Set Up Your Flask Application

First, create a simple Flask application. Here’s a basic example you can use:

# app.py
from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8080)

Directory Structure

Organize your files as follows:

/my-flask-app
    ├── app.py
    └── requirements.txt

Create requirements.txt

In the same directory, create a requirements.txt file to specify the dependencies:

Flask==2.0.1

Step 2: Create a Dockerfile

Next, create a Dockerfile in the same directory to containerize your application:

# Dockerfile
FROM python:3.9-slim

WORKDIR /app

COPY requirements.txt requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

COPY . .

CMD ["python", "app.py"]

Explanation of the Dockerfile

• FROM: Specifies the base image (Python 3.9-slim).
• WORKDIR: Sets the working directory inside the container.
• COPY: Copies the dependency file and then the entire application into the container.
• RUN: Installs the dependencies.
• CMD: Defines the command to run your application.

Step 3: Build the Docker Image

Open your terminal, navigate to the directory containing your files, and run the following command to build your Docker image:

docker build -t my-flask-app .

Step 4: Test the Docker Container Locally

Before deploying to Google Cloud, it’s a good practice to test your Docker container locally. Run the following command:

docker run -p 8080:8080 my-flask-app

Now, visit http://localhost:8080 in your browser, and you should see “Hello, World!” displayed.

Step 5: Push Your Docker Image to Google Container Registry

1. Authenticate with Google Cloud:

bash gcloud auth login

1. Set the project ID:

bash gcloud config set project YOUR_PROJECT_ID

1. Tag your Docker image:

bash docker tag my-flask-app gcr.io/YOUR_PROJECT_ID/my-flask-app

1. Push the image to Google Container Registry:

bash docker push gcr.io/YOUR_PROJECT_ID/my-flask-app

Step 6: Deploy to Google Cloud Run

Now that your Docker image is in Google Container Registry, you can deploy it to Google Cloud Run.

1. Deploy the application:

bash gcloud run deploy my-flask-app --image gcr.io/YOUR_PROJECT_ID/my-flask-app --platform managed

1. Follow the prompts to select the region and allow unauthenticated invocations if needed.

2. Access your application: Once deployed, Google Cloud will provide you with a URL where your application is hosted.

Troubleshooting Common Issues

• Image cannot be found: Ensure that you have pushed your Docker image to the correct Google Container Registry.
• Application not responding: Check the logs using gcloud logs read to troubleshoot any runtime errors.
• Port issues: Ensure that you are exposing the correct port (8080).

Conclusion

Deploying a Flask application on Google Cloud using Docker can significantly enhance your development workflow and application management. By following the steps outlined in this guide, you can leverage the power of cloud computing to run your applications reliably and efficiently.

As you become more comfortable with these tools, explore additional features like scaling and monitoring your application on Google Cloud to optimize performance further. Happy coding!