Use Docker Compose for an app and database

Compose can make a multi-service development environment repeatable, but start order alone does not mean the database is ready.

Inspect the service contract

The integration lab builds a Compose-shaped fixture.

from integration_cases import compose_case

result = compose_case()
assert result["services"] == ["app", "db"]
assert result["db_healthcheck"] is True
assert result["persistent_volume"] is True
assert result["secrets_embedded"] is False
assert result["compose_started"] is False

Use service DNS names, health checks, explicit networks and a named volume for local persistence. Run migrations as a controlled task rather than every replica racing. Keep defaults/dummy values in version control and inject secrets using appropriate local mechanisms.

Add reset and restore commands, resource limits where useful and a health-aware dependency. Test cold start, restart, schema migration and volume deletion in a disposable environment. Compose parity is helpful but does not prove cloud behaviour.

The FDE for Freshers course uses Compose to teach the boundary between application and database.

Exercise

Start an app/database stack, run an integration test, restart the app and verify data persists. Then reset safely and document the consequence.

Continue learning

This article is part of the FDE integration and deployment foundations sequence. Use the neighbouring tasks when you need the prerequisite or the next application.

• Review the prerequisite or neighbouring task in Write a Dockerfile for a small Python service.
• Continue with Create a CI workflow that runs meaningful tests.

Reference: Docker Compose services.