Traefik with multiple docker-compose.yml files - docker-compose

Question

Hello traefik friends.
I just started to look into traefik. All tutorials show how to run one docker-compose.yml file with traefik togather with other containers. I most often have many separate docker-compose.yml files and very much would like to use them with traefik.
so here is my code for traefik container:
version: "3.3"
services:
traefik:
image: "traefik:v2.5"
container_name: "traefik"
command:
#- "--log.level=DEBUG"
- "--api.insecure=true"
- "--providers.docker=true"
- "--providers.docker.exposedbydefault=false"
- "--entrypoints.websecure.address=:443"
- "--certificatesresolvers.myresolver.acme.tlschallenge=true"
#- "--certificatesresolvers.myresolver.acme.caserver=https://acme-staging-v02.api.letsencrypt.org/directory"
- "--certificatesresolvers.myresolver.acme.email=xxxxxxxxx#gmail.com"
- "--certificatesresolvers.myresolver.acme.storage=/letsencrypt/acme.json"
ports:
- "443:443"
- "8080:8080"
networks:
- "traefik"
- "external"
volumes:
- "./letsencrypt:/letsencrypt"
- "/var/run/docker.sock:/var/run/docker.sock:ro"
and the other exemplary docker-compose I would like to use with traefik:
version: '3.1'
services:
php:
image: php:7.4-apache
ports:
- 8081:80
volumes:
- ./php/www:/var/www/html/
labels:
- "traefik.enable=true"
- "traefik.http.routers.php.rule=host(`php.xxxxxx.com`)"
- "traefik.http.routers.php.entrypoints=websecure"
- "traefik.http.routers.php.tls.certresolver=myresolver"
unfortunately that doesnt seem to work (when I concat theese to files into one big docker-compose.yml file - it works fine. Could you point me in the right direction?

Answer 1

Traefik needs to be part of the networks for all the services it connects to. For me it works when I set network: host for Traefik. (And then you have to remove ports part.)
I do wonder how safe that is, I can't seem to access the admin interface from another machine, so that's good.

Answer 2

Each docker-compose.yml by default create its own network. So traefik from the traefik network can't access PHP server from some other "php-default" network.
see Compose Networking docs
We have to add the PHP server to the traefik network:
php/docker-compose.yml:
services:
php:
image: php:7.4-apache
# we need to tell the traefik what port is the container listening to
expose:
- 80
volumes:
- ./php/www:/var/www/html/
labels:
- "traefik.enable=true"
- "traefik.http.routers.php.rule=host(`php.xxxxxx.com`)"
- "traefik.http.routers.php.entrypoints=websecure"
- "traefik.http.routers.php.tls.certresolver=myresolver"
networks:
default:
name: traefik
external: true
OR if you want to have other networks
services:
php:
...
networks:
- traefik
...
networks:
traefik:
external: true
Note there is not defined port property, instead there is expose. The port exposes ports on the host, the expose act as mere documentation (see this Q) but the traefik read it.
And because of that, I think that in your traefik/docker-compose.yml the external network is unnecessary.