Traefik not set backend/frontend in swarm mode - traefik

Question

i would like use traefik in a cluster swarm, following this guide https://docs.traefik.io/user-guide/swarm-mode/#deploy-traefik i've write this stack file:
traefik:
image: traefik:alpine
deploy:
placement:
constraints:
- node.role == manager
command: --api --docker --docker.watch --docker.swarmMode
volumes:
- /var/run/docker.sock:/var/run/docker.sock
ports:
- "80:80"
- "8080:8080"
labels:
- "traefik.enable=false"
backend:
image: registry.example.com/backend
labels:
- "traefik.backend=backend"
- "traefik.backend.buffering.maxRequestBodyBytes=2147483648"
- "traefik.backend.loadbalancer.sticky=true"
- "traefik.frontend.rule=Host:backend.localhost"
- "traefik.frontend.passHostHeader=true"
- "traefik.port=80"
api:
image: registry.example.com/api
labels:
- "traefik.backend=api"
- "traefik.backend.buffering.maxRequestBodyBytes=2147483648"
- "traefik.backend.loadbalancer.sticky=true"
- "traefik.frontend.rule=Host:api.localhost"
- "traefik.frontend.passHostHeader=true"
- "traefik.port=80"
Traefik start but nothing is configured, I can not understand where is the error.

Answer 1

You forgot the network part from the example.
You miss both network related labels and the networks itslelf:
deploy:
labels:
- "traefik.docker.network=traefik-network" # for both api and backend
...
networks:
- "traefik-network" # for traefik, api and backend
...
networks:
traefik-network:{} # you can also make it external
EDIT :
also, on swarm, the labels should be set under the "deploy" section of your service, and not ont the service itself.