Better "Best Practices" regarding Docker networks

[kmarius]

The section about Docker networks in the Advanced Configuration suggests to replace the default network in each compose with a network shared with NPM. This can lead to strange issues like this one where multiple instances of redis clashed because they were in the same network, affecting users of NPM, caddy and traefik alike. Additionally, all containers in this network can reach all other containers.

A preferred solution would be to only add front-end services to the shared network, and leave all backend services in the respective default networks created for each compose file. Two situations arise:

1. There is only one service in the compose. We can simply append the network: snippet as already suggested to replace the default network:

networks:
  default:
    external: true
    name: npmnet

2. If there is more than one service, append this snippet instead:

networks:
  npmnet:
    external: true

and add the following snippet only to the front-end service (or adjust the existing one), leave all other services as is:

networks:
  - npmnet
  - default

(replace npmnet with the name of the shared network)