Runtime

Zombie processes in your containers? Slow shutdowns? Your app shouldn’t run as PID 1. Here’s the simple fix. The problem When your app runs as PID 1, it has special responsibilities: Handle system signals (SIGTERM, SIGINT) Reap zombie processes Forward signals to child processes Most apps (especially Node.js, Python) don’t handle these well. The solution Add init: true to your service: services: app: image: node:20 init: true # Adds Tini as PID 1 command: node server.js Docker automatically injects a tiny init system (Tini) that handles PID 1 responsibilities properly. ...

Stop doing docker compose down && docker compose up for every code change. Docker Compose lets you restart individual services while keeping the rest running. The solution Restart just what changed: # Restart only the web service docker compose up -d web # Your database, cache, and queue keep running! This simple command saves minutes per restart. Your database keeps its data, Redis maintains its cache, message queues preserve their state. ...

“Connection refused” errors? The app starts before the database is ready. Here’s the fix. What doesn’t work This only waits for the container to start, not for it to be ready: services: app: depends_on: - db # Container starts, but database isn't ready yet What actually works Add health checks: services: db: image: postgres:16 environment: POSTGRES_PASSWORD: secret healthcheck: test: ["CMD-SHELL", "pg_isready -U postgres"] interval: 10s timeout: 5s retries: 5 start_period: 10s app: image: myapp depends_on: db: condition: service_healthy # Now it actually waits for the database Common health checks PostgreSQL: ...