Traefik with docker-compose creates too many frontends

Question

I want to use multiple docker-compose projects with Traefik as reverse proxy. After following the documentation I've created two docker-compose files; one for Traefik and one for an example project which has 2 "whoami" containers.

This works great for the backends, but it seems that Traefik creates one frontend per running container. So instead of 1 frontend for the 2 whoami containers, I got two frontends defined: "frontend-Host-whoami-localhost-0" and "frontend-Host-whoami-localhost-1".

Traefik will create more frontends if I scale up the whoami service (by either duplicating their definition in the docker-compose.yaml file, or with docker-compose scale whoami=10).

I just want one frontend for the "Host:whoami.localhost" rule, which points to one backend with multiple running containers attached to it. How can I do this?

traefik.toml:

defaultEntryPoints = ["http"]

[web]
address = ":8080"

[entryPoints]
    [entryPoints.http]
    address = ":80"

[docker]
endpoint = "unix:///var/run/docker.sock"
domain = "localhost"

docker-compose.yaml (for traefik):

version: "2"
services:
  traefik:
    container_name: traefik
    image: traefik
    networks:
      - webgateway
    ports:
      - "80:80"
      - "8080:8080"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - ./traefik.toml:/traefik.toml
    labels:
      traefik.backend: web
      traefik.frontend.rule: Host:monitor.localhost

networks:
  webgateway:
    driver: bridge

whoami/docker-compose.yaml:

version: "2"
services:
  whoami:
    image: emilevauge/whoami
    networks:
      - webgateway
    labels:
      traefik.backend: whoami
      traefik.frontend.rule: Host:whoami.localhost

  whoami_2:
    image: emilevauge/whoami
    networks:
      - webgateway
    labels:
      traefik.backend: whoami
      traefik.frontend.rule: Host:whoami.localhost

networks:
  webgateway:
    external:
      name: traefikdocker_webgateway

Answer 1

I suppose you want that:

http://example.com/
|-> app1 who serve http://example.com/foo
|-> app2 who serve http://example.com/bar

To do that you must use another matcher (like PathPrefix by example):

traefik.frontend.rule: Host:http://example.com/; PathPrefix:/foo
|-> app1 who serve http://example.com/foo

traefik.frontend.rule: Host:http://example.com/; PathPrefix:/bar
|-> app2 who serve http://example.com/bar

If you just want to scale, you only need one service in your composefile:

traefik.frontend.rule: Host:http://example.com/
|-> 10 x app (docker-compose scale app=10)