Hey guys! I'm transitioning from the Spring Boot ecosystem to deploying a FastAPI-based Python application. In Spring Boot, we typically use a UBI-based Docker image to deploy our self-contained `.jar` files to Kubernetes pods, which is pretty straightforward. I'm looking for advice on the standard practices for deploying a self-contained FastAPI app in a Docker image. Is it common or considered good practice to encapsulate the entire FastAPI application in the Docker image? What configurations or steps should I follow for this deployment?
5 Answers
You should start with a base container image that includes the Python version your application uses. Copy your application code and the `requirements.txt` file, which contains all your dependencies—if you don't have one, just run `pip freeze` to generate it. Install those dependencies within the container, and set your entry point to the main app file like `app.py` or `main.py`. Just remember, don't copy your virtual environment; it's unnecessary and will bloat your image.
I usually package my FastAPI application as a wheel and then use a minimal base image to pip install that package. This method handles dependencies well while providing a start script. But I’m open to hearing about other strategies!
In my opinion, it's best to create all application images for K8S with deployment in mind, regardless of the programming language. Ensure your FastAPI app is self-contained—this way, whoever sets up the K8S deployment can seamlessly integrate your image like any other. Use a lightweight Python base image, install the necessary packages via pip, set the appropriate entry point, and you're pretty much set!
For Python apps, I prefer using UV (instead of pip) for package management since it generates a lock file, ensuring consistency. Also, copy your virtual environment out to a separate build stage to keep your Docker image lighter. I use a multi-stage Dockerfile where the first stage builds the app and the second runs it from a minimal image. Just be cautious with dependencies and packaging!
While there isn't a rigid standard, a common practice is to structure your FastAPI application as a Kubernetes deployment with a service running on a WSGI server like Gunicorn or Uvicorn, and expose it through an Ingress controller like ingress-nginx. If you need a reference, I have a sample manifest that outlines a basic setup for deploying a FastAPI app with Ingress, along with some security measures and volume mounts. It can provide a solid starting point!
That sounds helpful! Can you share that manifest, please?
Great approach! Keeping it language-agnostic makes it easier for Ops teams to manage.