Docker containerization in FastAPI

Introduction

Docker containerization helps you package your FastAPI app with everything it needs to run. This makes it easy to share and run your app anywhere without setup problems.

You want to run your FastAPI app on different computers without installing Python or dependencies each time.

You need to share your FastAPI app with teammates or deploy it to a cloud server easily.

You want to keep your app isolated so it doesn't conflict with other software on your machine.

You want to create a consistent environment for your app during development and production.

You want to automate app deployment with tools that support Docker containers.

Syntax

FastAPI

FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

FROM sets the base image with Python installed.

WORKDIR sets the folder inside the container where commands run.

Examples

Basic Dockerfile to run a FastAPI app with dependencies installed.

FastAPI

FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install -r requirements.txt
COPY . .
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Installs FastAPI and Uvicorn directly without a requirements file.

FastAPI

FROM python:3.12-slim
WORKDIR /app
COPY . .
RUN pip install fastapi uvicorn
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Adds EXPOSE to tell Docker which port the app listens on.

FastAPI

FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
EXPOSE 8000
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Sample Program

This Dockerfile sets up a FastAPI app container. It starts from a small Python image, installs dependencies from requirements.txt, copies the app code, exposes port 8000, and runs the app with Uvicorn.

FastAPI

FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
EXPOSE 8000
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Important Notes

Make sure your requirements.txt lists all needed packages like fastapi and uvicorn.

Use docker build -t myfastapiapp . to build the container image from this Dockerfile.

Run your container with docker run -p 8000:8000 myfastapiapp to access the app at http://localhost:8000.

Summary

Docker packages your FastAPI app and its environment into a container.

This container runs the app the same way on any computer or server.

Use a Dockerfile to define how to build your app container step-by-step.