SSG DB access with Docker build

[orbiteleven]

I'm trying to "Dockerize" my Next.js app and running into a problem. Possibly/probably of my own doing, but still.

I have a Dockerized Postgres image to run my database. That is up and running, but when I try to build my app via Docker (via docker build -f Dockerfile), everything works up until the point it tries to build the SSG pages:

Error: Can't reach database server at `localhost`:`5432`

I've tried using depends_on in a docker-compose.yml, passing various things into --add-host, as well as replacing localhost with host.docker.internal in my .env file, but nothing seems to work. I know this is more of a Docker thing, and I'll probably cross-post this to SO, but since it feels like a pretty common sense way to Dockerize a Next.js app with SSG, perhaps someone here has pointers.

FWIW I'm using a lightly modified version of https://github.com/vercel/next.js/tree/canary/examples/with-docker

thanks

[orbiteleven]

Classic rubber duck posting, but in case someone else is searching:

The issue I had was that I was adding network: host to the service, but not build. So while this didn't work:

services:
  web:
    # network listed on service:web
    network: host
    depends_on:
      db:
        condition: service_healthy
      redis:
        condition: service_healthy
    build:
      context: .
      dockerfile: ./packages/web/Dockerfile
    volumes:
      - .:/app
    ports:
      - 3000:3000
      - 5432:5432
      - 6379:6379

This did:

services:
  web:
    depends_on:
      db:
        condition: service_healthy
      redis:
        condition: service_healthy
    build:
      context: .
      # network listed on service:web:build
      network: host
      dockerfile: ./packages/web/Dockerfile
    volumes:
      - .:/app
    ports:
      - 3000:3000
      - 5432:5432
      - 6379:6379

[FadyAmir223]

I have been searching for this for about 25 days.
Thank you so much, I didn't even imagine that build would have this option

[Quozzo]

For those still struggling to get this working, the db connection string cannot be db:5432 or postgres:5432 or whatever you called your service in the docker compose file. It needs to be the IP Address of the container itself.

As far as I understand it, the host network doesn't resolve the named DNS addresses within docker, but it does know ip addresses.

[Nithur-M]

Hey @Quozzo! How do you know the ip of the container? I am new to docker tbf. Here is how I am dealing with it: passing a temp env var to the docker build context with localhost as hostname. I spent nearly 2 weeks on this issue. I would love to try your approach as well.

[Nithur-M]

Ok, I found my IP of the docker.

To add to your comment for those who will come into this issue in the future - the IP should be that of the container of the db, not the app.