Production: Docker and Observability

Uvicorn workers, health checks, structured logs and tracing.

• Advanced
• 16 min read
• 3 objectives

Before this lessonLesson 14: Custom OpenAPI and Docs

Production FastAPI is an ASGI server, several workers, a reverse proxy, and enough observability to debug the next outage.

Docker

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", "--workers", "2"]

For a lot of blocking I/O, more workers help. For a lot of async def waiting on the network, fewer workers and a bigger event loop often win. Measure.

Health and readiness

@app.get("/health", include_in_schema=False)
def health(db: Session = Depends(get_db)):
    db.execute(text("SELECT 1"))
    return {"status": "ok"}

Structured logs

import logging, json

class JsonLog(logging.Formatter):
    def format(self, rec):
        return json.dumps({"level": rec.levelname, "msg": rec.getMessage()})

logging.basicConfig(level="INFO")
logging.getLogger().handlers[0].setFormatter(JsonLog())

• Put a request id on every log line (middleware).
• Do not log tokens, passwords or full request bodies.
• Export OpenTelemetry traces if you have more than one service.