Portainer in Docker swarm stack with Traefik refuses to connect - docker

Question

I am trying to include Portainer in a docker-compose swarm, consisting of WordPress + MySQL and Traefik (reverse proxy). I am using the following definition:
version: '3'
services:
traefik:
image: "traefik:v2.0.0-rc3"
command:
- "--api.insecure=true"
- "--providers.docker=true"
- "--providers.docker.swarmmode=true"
- "--providers.docker.exposedbydefault=false"
- "--entrypoints.web.address=:80"
ports:
- "80:80"
- "8080:8080"
volumes:
- /var/run/docker.sock:/var/run/docker.sock
networks:
- traefik
deploy:
mode: global
placement:
constraints: [node.role==manager]
portainer:
image: portainer/portainer:latest
command: -H unix:///var/run/docker.sock
volumes:
- /var/run/docker.sock:/var/run/docker.sock
- ./portainer:/data
networks:
- traefik
deploy:
mode: replicated
replicas: 1
placement:
constraints: [node.role==manager]
restart_policy:
condition: on-failure
delay: 5s
max_attempts: 3
labels:
- "traefik.enable=true"
- "traefik.http.routers.portainer.entrypoints=web"
db:
image: mysql:5.7
volumes:
- ./db/initdb.d:/docker-entrypoint-initdb.d
networks:
- traefik
environment:
MYSQL_ROOT_PASSWORD: <root_password>
MYSQL_DATABASE: <db_name>
MYSQL_USER: <db_user>
MYSQL_PASSWORD: <user_password>
deploy:
replicas: 1
restart_policy:
condition: on-failure
delay: 5s
max_attempts: 3
app:
image: my-repo/wordpress:latest
networks:
- traefik
deploy:
replicas: 2
restart_policy:
condition: on-failure
delay: 5s
max_attempts: 3
labels:
- "traefik.enable=true"
- "traefik.http.routers.app.rule=Host(`example.org`)"
- "traefik.http.routers.app.entrypoints=web"
- "traefik.http.services.app.loadbalancer.server.port=80"
networks:
traefik:
Everything works except portainer. When I visit localhost:9000 I just get a refused connection. The following non-swarm-mode docker-compose works, however:
version: '3'
services:
traefik:
image: "traefik:v2.0.0-rc3"
container_name: "traefik"
restart: always
command:
- "--api.insecure=true"
- "--providers.docker=true"
- "--providers.docker.exposedbydefault=false"
- "--entrypoints.web.address=:80"
ports:
- "80:80"
- "8080:8080"
volumes:
- /var/run/docker.sock:/var/run/docker.sock
networks:
- traefik
portainer:
image: portainer/portainer
command: -H unix:///var/run/docker.sock
restart: always
volumes:
- /var/run/docker.sock:/var/run/docker.sock
- ./portainer:/data
ports:
- "9000:9000"
- "8000:8000"
networks:
- traefik
labels:
- "traefik.enable=true"
- "traefik.http.routers.portainer.entrypoints=web"
db:
image: mysql:5.7
restart: always
volumes:
- ./db/initdb.d:/docker-entrypoint-initdb.d
networks:
- traefik
environment:
MYSQL_ROOT_PASSWORD: <root_password>
MYSQL_DATABASE: <db_name>
MYSQL_USER: <db_user>
MYSQL_PASSWORD: <user_password>
app:
image: my-repo/wordpress:latest
restart: always
depends_on:
- db
networks:
- traefik
labels:
- "traefik.enable=true"
- "traefik.http.routers.app.rule=Host(`example.org`)"
- "traefik.http.routers.app.entrypoints=web"
networks:
traefik:
What am I doing wrong? The logs in each case are the same. In non-swarm-mode I can log in to the Portainer UI and see all my containers running, etc. But the swarm version simply refuses to connect, even when I pass Host rule (portainer.example.org). I have only been using Traefik for a few days, and am very likely to be making a simple configuration error (hopefully!).

Answer 1

Port Detection
Docker Swarm does not provide any port detection information to Traefik.
Therefore you must specify the port to use for communication by using the label traefik.http.services.<service_name>.loadbalancer.server.port (Check the reference for this label in the routing section for Docker).