Debugging

Know the difference between exec and run! Each has its place in your debugging toolkit. The key difference exec: Runs commands in an existing container run: Creates a new container # Exec: enters running container docker compose exec web bash # Run: starts new container docker compose run web bash When to use exec Use exec for debugging running services: # Debug a running web server docker compose exec web bash # Check logs inside container docker compose exec web tail -f /var/log/app.log # Run database queries docker compose exec db psql -U postgres # Check process list docker compose exec web ps aux # Test connectivity from inside docker compose exec web curl http://api:3000/health Important: Container must be running! ...

Track everything happening in your Compose stack! Events provide real-time insights into container lifecycle changes. Basic event monitoring Watch events as they happen: # Stream all events docker compose events # JSON format for parsing docker compose events --json # Specific services only docker compose events web worker # Since a specific time docker compose events --since "2026-02-06T10:00:00" Event types Common events you’ll see: container create # Container created container start # Container started container stop # Stop initiated container die # Container exited container destroy # Container removed health_status # Health check changed network connect # Network attached network disconnect # Network detached Processing events Parse with jq: ...

Stop scrolling through endless output. Master docker compose logs options to find issues fast and monitor services effectively. Basic commands # All service logs docker compose logs # Single service docker compose logs web # Multiple services docker compose logs web worker Follow logs in real-time Watch logs as they happen: # Follow all services docker compose logs -f # Follow specific service docker compose logs -f api # Start fresh and follow docker compose logs -f --since 1m Tail recent logs Get last N lines: ...