Docker Lab — Hardened and Observable LLMOps API

This lab packages a deterministic FastAPI application as an operational control. It requires no API keys and does not call an LLM: this allows you to isolate build, health, signals, metrics, and container security before adding an external dependency.

What it demonstrates#

• multi-stage build with uv 0.12.5 and pinned dependencies (catalog dated 2026-08-21);
• slim runtime without compiler, UID/GID 10001 process, and CMD exec;
• separate health/readiness checks with no paid API calls;
• read-only filesystem, dropped capabilities, and no-new-privileges in Compose;
• Prometheus metrics without user labels or prompt data;
• Prometheus image pinned to v3.14.0 and 24-hour local retention.

Periodically revalidate versions and digests; a pinned tag reduces drift, but does not replace a scanner or an update policy.

Run#

From this directory:

docker compose config --quiet
docker compose build
docker compose up -d --wait
curl -fsS http://127.0.0.1:8000/health
curl -fsS http://127.0.0.1:8000/ready
curl -fsS -X POST http://127.0.0.1:8000/v1/answer \
  -H 'content-type: application/json' \
  -d '{"question":"He expuesto una clave API, ¿qué hago?"}'
curl -fsS http://127.0.0.1:8000/metrics | head

Prometheus is available at http://127.0.0.1:9090. Query:

sum by (endpoint, status) (rate(llmops_requests_total[1m]))

To stop without deleting the metrics volume:

docker compose down

Reading the Dockerfile#

1. uv-bin sets the build tool.
2. builder creates /opt/venv; copying requirements.txt first preserves the cache.
3. runtime receives only Python, the venv, and app.py.
4. The non-root user has no shell or writable home directory.
5. The health check uses the stdlib; it does not install curl at runtime.
6. Uvicorn is PID 1 and receives SIGTERM directly.

Acceptance tests#

docker compose ps
docker inspect --format '{{.Config.User}} {{.HostConfig.ReadonlyRootfs}}' llmops-docker-api-1
docker compose exec api python -c 'import os; print(os.getuid())'
docker compose exec api sh -c 'touch /app/forbidden'

The UID must be 10001, ReadonlyRootfs must be true, and the last command must fail. The generated container name may vary: docker compose ps -q api returns its ID if you need a portable command.

Evolution towards a real API#

Inject keys from the orchestrator's secret manager, add an async client with timeout, circuit breaker, and budget, and keep /health provider-free. Never add prompt or user ID as a Prometheus label: this creates unbounded cardinality and leaks data. Detailed traces belong to a tracing backend with defined authoring and retention policies.