Docker, docker-compose, restart: unless-stopped loose logs in console

Question

I have a docker-compose.yml version 3 which works very good:

version: '3'

services:

  db:
    image: postgres
    restart: unless-stopped
    ports:
      - "5432:5432"

redis:
    image: redis
    restart: unless-stopped
    ports:
      - "6379:6379"

  app:
    build: .
    restart: unless-stopped
    command: bash ./script.sh
    volumes:
      - bundle:/bundle
    ports:
      - "3000:3000"
      - "1234:1234"
    depends_on:
      - db
      - redis
    stdin_open: true
    tty: true

volumes:

  bundle: {}

I use it with Rails and I debug attaching from Windows port 1234. Everything works good.

But.

Sometimes my Rails server crash. It happens. So I need the app container restart itself. And it does. But I lose the logs in my powershell console.

When starting with docker-compose up I see everything.

When the app container crash and restart itself I don't see anything from the "new" app container. Why?

If I close manually that app container and start it manually all logs from the before restarted container appears again scrolling down like the Niagara Falls!

Bug? My own bug?

Solution

Easy Answer, it's neither a docker bug nor a bug on your end =)

Docker logs are attached to containers respectively, so when you're trying to see the logs (after your new app container has been created) you'll notice that it's empty and there's no history to scroll up for. While in fact the logs you're looking for were attached to your old container that has been removed and replaced by the new app container.

as a work around, just always mount volume the log files from within your rails app to outside docker, that way you wont lose any data.

the logs/data will be persistent even if you stop or remove the container.