docker compose traefik dns resolving inter containers

compose.yml

version: "3.3"

services:
  traefik:
    image: "traefik:v3.0"
    container_name: "traefik"
    command:
      #- "--log.level=DEBUG"
      - "--api.dashboard=true"
      - "--ping=true"
      - "--api.insecure=true"
      - "--providers.docker=true"
      - "--providers.docker.exposedbydefault=false"
      - "--entrypoints.web.address=:80"
      - "--providers.docker.network=traefik_proxy"
    networks:
      traefik_proxy:
        aliases:
          - whoami.localhost # insert here every others traefik-exposed containers' domains
          - traefik.localhost
    labels:
      traefik.enable: "true"
      traefik.http.routers.dashboard.rule: Host(`traefik.localhost`)
      traefik.http.routers.dashboard.service: api@internal
    ports:
      - "80:80"
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock:ro"

  whoami:
    image: "traefik/whoami"
    container_name: "whoami"
    networks:
      - traefik_proxy
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.whoami.rule=Host(`whoami.localhost`)"
      - "traefik.http.routers.whoami.entrypoints=web"

  curl:
    image: curlimages/curl:8.6.0
    command: "whoami.localhost"
    networks:
      - traefik_proxy
    depends_on:
      whoami:
        condition: service_started

networks:
  traefik_proxy:

docker_compose_traefik_dns.md

In a docker-compose context, with a traefik container, by default a container cannot resolve the rule/host of another container.

2 solutions :

1. use network aliases (https://docs.docker.com/compose/compose-file/compose-file-v3/#aliases) => cf compose.yml
2. use dnsmasq on the host to forward every dns requests for a TLD/domaine (eg. *.localhost) to traefik

• https://www.adaltas.com/fr/2022/11/17/traefik-docker-dnsmasq/
• https://www.reddit.com/r/Traefik/comments/k8g00d/comment/gf1csc6/