Accessing Postgres server from a secondary docker container without db.py

[Paul Ellis]

How do I do connect to a prostgres server using PyDAL but without a db.py in the secondary container or having all the tables drop when I connect without a db definition?

I have a server running docker with containers for the nginx proxy, lets encrypt, web2py and postgres.

one docker_compose.yml brings up nginx and lets encrypt and makes a docker network.

version: '3'

services:
  nginx:
    image: nginx:1.13.1
    container_name: nginx-proxy
    ports:
      - "80:80"
      - "443:443"
      - "8080:8080"
    volumes:
      - conf:/etc/nginx/conf.d
      - vhost:/etc/nginx/vhost.d
      - html:/usr/share/nginx/html
      - certs:/etc/nginx/certs
    labels:
      - "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true"

  dockergen:
    image: jwilder/docker-gen:0.7.3
    container_name: nginx-proxy-gen
    depends_on:
      - nginx
    command: -notify-sighup nginx-proxy -watch -wait 5s:30s /etc/docker-gen/templates/nginx.tmpl /etc/nginx/conf.d/default.conf
    volumes:
      - conf:/etc/nginx/conf.d
      - vhost:/etc/nginx/vhost.d
      - html:/usr/share/nginx/html
      - certs:/etc/nginx/certs
      - /var/run/docker.sock:/tmp/docker.sock:ro
      - ./nginx.tmpl:/etc/docker-gen/templates/nginx.tmpl:ro

  letsencrypt:
    image: jrcs/letsencrypt-nginx-proxy-companion
    container_name: nginx-proxy-le
    depends_on:
      - nginx
      - dockergen
    environment:
      NGINX_PROXY_CONTAINER: nginx-proxy
      NGINX_DOCKER_GEN_CONTAINER: nginx-proxy-gen
    volumes:
      - conf:/etc/nginx/conf.d
      - vhost:/etc/nginx/vhost.d
      - html:/usr/share/nginx/html
      - certs:/etc/nginx/certs
      - /var/run/docker.sock:/var/run/docker.sock:ro

volumes:
  conf:
  vhost:
  html:
  certs:

# Do not forget to 'docker network create nginx-proxy' before launch, and to add '--network nginx-proxy' to proxied containers.

networks:
  default:
    external:
      name: nginx-proxy

the 'web2py' docker_compose.yml brings up the db and web2py container and connects to the nginx network.

version: '3'

services:

  db:
    image: postgres:11
    restart: always
    env_file:
        ./config/db/db_env
    expose:
        - 5432
    volumes:
      - db_volume:/var/lib/postgresql/data
     
  angebotstool:
    build: .
    volumes:
      - web2py_apps:/home/act/web2py/applications
    expose:
      - 80
      - 443

    environment:
      VIRTUAL_HOST: foo.barr.com
      LETSENCRYPT_HOST: foo.barr.com
      LETSENCRYPT_EMAIL: foo@bar.com
    depends_on:
      - db

     
volumes:
    db_volume:
        driver: local
        driver_opts:
            type: 'none'
            o: 'bind'
            device: '/home/act/databases/'
    web2py_apps:
        driver: local
        driver_opts:
            type: 'none'
            o: 'bind'
            device: '/home/act/web2py-gunicorn/web2py/applications'
       
networks:
    default:
        external:
            name: nginx-proxy

This was mostly configured with luck and trial and error. I am still learning in this area.

Now I would like to have a container running Scrapy or similar which will periodically log into a site and update the product information (when required).

I want to use PyDAL to connect to the existing database. The Scrapy container will be configured in the 'web2py' docker_compose.yml.

How do I do this without having to maintain another db.py in the secondary container or having all the tables drop when I connect without a db definition?