07-apis-with-fastapi

Building DevOps APIs with FastAPI

Teams often trigger automation, health checks, and reporting through APIs. This module turns your Python logic into a real HTTP service with FastAPI.

Start with a one-file "hello" API, then study a full Internal DevOps Utilities API that exposes system metrics, log analysis, and AWS info — with routers, services, auto-generated docs, and a Dockerfile.

What you'll learn

• Build an API with FastAPI and run it with uvicorn
• The request/response flow and JSON responses
• Organize a real app into routers/ (HTTP) and services/ (logic)
• Reuse the log-analyzer and metrics logic from earlier modules
• Explore the auto-generated Swagger docs at /docs

Files

• hello_api.py — the smallest possible FastAPI app
• devops-utilities-api/ — the full app (routers, services, Dockerfile)

Quick start

pip install fastapi uvicorn psutil boto3
uvicorn hello_api:app --reload
# open http://127.0.0.1:8000/docs

The full app

cd devops-utilities-api
pip install -r requirements.txt
python main.py           # uvicorn on http://0.0.0.0:8000

curl http://127.0.0.1:8000/           # hello
curl http://127.0.0.1:8000/health     # {"status":"ok"}
curl http://127.0.0.1:8000/metrics    # CPU/mem/disk
curl http://127.0.0.1:8000/logs       # analyze bundled app.log
curl http://127.0.0.1:8000/aws/s3     # needs AWS creds

Interactive docs: http://127.0.0.1:8000/docs

Practice

Extend the utilities API (work in devops-utilities-api/):

1. Add a /version endpoint returning {"version": "1.2.0"}.
2. Add /logs/errors returning only the ERROR count (reuse services/logs_service.py).
3. Add a cpu_threshold query param to /metrics (e.g. /metrics?cpu_threshold=50).
4. Bonus: build the Docker image and hit /health.