Full-stack docker-compose: app + emulator + observability

A "production-shaped" compose stack:

• bqemulator (the emulator, exposing Prometheus metrics).
• app — a tiny Python service that reads from bqemulator.
• prometheus — scrapes the emulator's /metrics endpoint.
• grafana — pre-provisioned with a Prometheus datasource and a starter dashboard.

This is the canonical local-development setup for teams adopting bqemulator who want one docker compose up to give them the complete dev environment.

Layout

docker-compose.yml
app/Dockerfile
app/server.py
prometheus/prometheus.yml
grafana/provisioning/datasources/prometheus.yml
grafana/provisioning/dashboards/dashboards.yml
grafana/provisioning/dashboards/bqemulator.json
seed.py                — seeds dataset + table on host
smoke-test.sh          — asserts each service is healthy and serving

Run

make test

make test:

1. docker compose up -d --build.
2. Waits for bqemulator, app, prometheus, grafana to be healthy.
3. Runs seed.py against the emulator.
4. Hits app:8080/customers and asserts a 3-row response.
5. Hits prometheus:9090/api/v1/query?query=up and asserts the emulator is up.
6. Hits grafana:3000/api/health and asserts database: ok.
7. docker compose down -v.

What to look for

• The emulator publishes Prometheus metrics on /metrics (see docs/guides/observability.md).
• Grafana is pre-provisioned via the provisioning/ directory — no manual UI clicks needed.
• The app container is intentionally tiny; the point is the composition, not the app code.