How to Build and Push a Python Docker Image to Google Artifact Registry¶

In this tutorial, we will create a simple Python "Hello World" application, containerize it using Docker, and push the image to the Google Cloud Artifact Registry repository we created in the previous step.

Prerequisites¶

Google Cloud Project with Artifact Registry API enabled.
Artifact Registry Repository: A Docker repository named my-docker-repo in us-central1 (created in the previous tutorial).
Docker installed on your local machine.
gcloud CLI installed and initialized.

Step 1: Create the Flask Application¶

Create a file named main.py with the following content:

# main.py
import os
from flask import Flask

app = Flask(__name__)

@app.route("/")
def hello_world():
    name = os.environ.get("NAME", "World")
    return f"Hello, {name} from Google Cloud Artifact Registry!"

if __name__ == "__main__":
    app.run(debug=True, host="0.0.0.0", port=int(os.environ.get("PORT", 8080)))

Step 2: Create requirements.txt¶

Create a file named requirements.txt to list the dependencies:

Flask==3.0.3

Step 3: Create the Dockerfile¶

Create a file named Dockerfile (no extension) in the same directory:

# Use an official Python runtime as a parent image
FROM python:3.12-slim

# Set the working directory in the container
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

# Make port 8080 available to the world outside this container
EXPOSE 8080

# Run main.py when the container launches
CMD ["python", "main.py"]

Step 4: Test Locally¶

Before pushing to the registry, it's a good practice to test the image locally.

Build the image locally:
```
docker build -t test-flask-app .
```
Run the container:
```
docker run -p 8080:8080 test-flask-app
```
Verify: Open your browser and go to http://localhost:8080. You should see the "Hello, World..." message.
Stop the container: Press Ctrl+C in the terminal to stop the container.

Step 5: Configure Docker Authentication¶

Before you can push images, you must configure Docker to authenticate with Google Cloud Artifact Registry.

gcloud auth configure-docker us-central1-docker.pkg.dev

Step 6: Build the Docker Image¶

Build the Docker image with a tag that points to your Artifact Registry repository.

Format: LOCATION-docker.pkg.dev/PROJECT-ID/REPOSITORY/IMAGE:TAG

Replace PROJECT_ID with your actual Google Cloud Project ID.

export PROJECT_ID=$(gcloud config get-value project)

docker build --platform linux/amd64 -t us-central1-docker.pkg.dev/$PROJECT_ID/my-docker-repo/python-hello-world:v1 .

Step 7: Push the Image to Artifact Registry¶

Now, push the tagged image to the repository:

docker push us-central1-docker.pkg.dev/$PROJECT_ID/my-docker-repo/python-hello-world:v1

Step 8: Verify the Push¶

You can verify that the image was pushed successfully by listing the images in your repository:

gcloud artifacts docker images list us-central1-docker.pkg.dev/$PROJECT_ID/my-docker-repo

Conclusion¶

You have successfully containerized a Python application and pushed it to Google Cloud Artifact Registry. You can now deploy this image to services like Cloud Run or Google Kubernetes Engine (GKE).