How to use internal networks with Traefik 2.x?

Question

I'm trying to setup a simple Nextcloud Stack with docker-compose and Traefik.

Here is my docker-compose.yml

version: '3.7'
services:
  nextcloud-database:
    image: mariadb
    container_name: nextcloud-database
    command: --transaction-isolation=READ-COMMITTED --binlog-format=ROW
    restart: always
    volumes:
      - $PWD/db:/var/lib/mysql
    env_file:
      - db.env
    networks:
      - backend
    logging:
      options:
        max-size: '12m'
        max-file: '5'
      driver: json-file

  nextcloud-redis:
    image: redis:alpine
    container_name: nextcloud-redis
    restart: always
    networks:
      - backend

  nextcloud-cron:
    image: nextcloud:latest
    container_name: nextcloud-cron
    restart: always
    volumes:
      - $PWD/cloud:/var/www/html
    entrypoint: /cron.sh
    networks:
      - backend

  nextcloud-app:
    image: nextcloud:latest
    container_name: nextcloud-app
    restart: always
    volumes:
      - $PWD/config:/var/www/html/config
      - $PWD/cloud:/var/www/html
      - $PWD/apps:/var/www/html/apps
      - $PWD/data:/var/www/html/data
    environment:
      - NEXTCLOUD_DATA_DIR=/var/www/html/data
      - MYSQL_HOST=nextcloud-database
    env_file:
      - db.env
    depends_on:
      - nextcloud-database
      - nextcloud-redis
      - nextcloud-cron
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.nextcloud.entrypoints=http"
      - "traefik.http.routers.nextcloud.rule=Host(`nextcloud.blablubb.de`)"
      - "traefik.http.middlewares.nextcloud-https-redirect.redirectscheme.scheme=https"
      - "traefik.http.routers.nextcloud.middlewares=nextcloud-https-redirect"
      - "traefik.http.routers.nextcloud-secure.entrypoints=https"
      - "traefik.http.routers.nextcloud-secure.rule=Host(`nextcloud.blablubb.de`)"
      - "traefik.http.routers.nextcloud-secure.tls=true"
      - "traefik.http.routers.nextcloud-secure.tls.certresolver=http"
      - "traefik.http.routers.nextcloud-secure.service=nextcloud"
      - "traefik.http.services.nextcloud.loadbalancer.server.port=80"
      - "traefik.docker.network=proxy"
    networks:
      - proxy
      - backend
    logging:
      options:
        max-size: '12m'
        max-file: '5'
      driver: json-file

networks:
  proxy: # this is the network provided by traefik
    external: true
  backend:
    external: false

and the db.env

MYSQL_PASSWORD="waff"
MYSQL_DATABASE=nextcloud
MYSQL_USER=nextcloud
MYSQL_ROOT_PASSWORD="waff"

The Nextcloud instance is reachable via the domain nextcloud.blablubb.de. So my question: What's needed that my nextcloud-docker container can communicate with each other? I thought it's handled through the backend network, but I've always error message, fe nextcloud-mysql isn't reachable.

Without Treafik this setup is working fine.

Thank you guys.

Answer 1

if you want two containers to be able to communicate with each other you need to have an overlay network and add both of the containers to the same network like

docker network create --driver=overlay --subnet=10.0.15.0/24  --attachable traefik

    networks:
      - backend

which is the case in your docker-compose file, here is an example for doing this

version: '3.7'

networks:
  traefik:
    external: true

volumes:
  db_data:

services:

  proxy:
    image: traefik:v2.1
    command:
      - '--providers.docker=true'
      - '--entryPoints.web.address=:80'
      - '--providers.providersThrottleDuration=2s'
      - '--providers.docker.watch=true'
      - '--providers.docker.swarmMode=true'
      - '--providers.docker.swarmModeRefreshSeconds=15s'
      - '--providers.docker.exposedbydefault=false'
      - '--providers.docker.defaultRule=Host("local.me")'
      - '--accessLog.bufferingSize=0'
    volumes:
      - '/var/run/docker.sock:/var/run/docker.sock:ro'
    ports:
      - '80:80'
    deploy:
      restart_policy:
        condition: any
        delay: 5s
        max_attempts: 3
        window: 120s
      update_config:
        delay: 10s
        order: start-first
        parallelism: 1
      rollback_config:
        parallelism: 0
        order: stop-first
    logging:
      driver: json-file
      options:
        'max-size': '10m'
        'max-file': '5'
    networks:
      - traefik

  mysql:
    image: mysql:5.7
    command: mysqld --general-log=1 --general-log-file=/var/log/mysql/general-log.log
    deploy:
      restart_policy:
        condition: any
        delay: 5s
        max_attempts: 3
        window: 120s
      update_config:
        delay: 10s
        order: start-first
        parallelism: 1
      rollback_config:
        parallelism: 0
        order: stop-first
    logging:
      driver: json-file
      options:
        'max-size': '10m'
        'max-file': '5'
    networks:
      - traefik
    volumes:
      - db_data:/var/lib/mysql
    environment:
      MYSQL_ROOT_PASSWORD: dummy
      MYSQL_DATABASE: rails_blog_production

  rails_blog_web:
    image: wshihadeh/rails_blog:demo-v1
    command: 'web'
    deploy:
      labels:
        - traefik.enable=true
        - traefik.http.services.blog.loadbalancer.server.port=8080
        - traefik.http.routers.blog.rule=Host(`blog.local.me`)
        - traefik.http.routers.blog.service=blog
        - traefik.http.routers.blog.entrypoints=web
        - traefik.docker.network=traefik
      restart_policy:
        condition: any
        delay: 5s
        max_attempts: 3
        window: 120s
      update_config:
        delay: 10s
        order: start-first
        parallelism: 1
      rollback_config:
        parallelism: 0
        order: stop-first
    logging:
      driver: json-file
      options:
        'max-size': '10m'
        'max-file': '5'
    networks:
      - traefik
    depends_on:
      - mysql
    environment:
      DATABASE_URL: mysql2://root:dummy@mysql/rails_blog_production
      RAILS_SERVE_STATIC_FILES: 'true'

one thing that is missing in your configurations is the linking between the services. For instance, you are providing the MySQL host in the application server but the port is missing.