Traefik super slow to pick up services on swarmmode

docker-compose-fast.yml

# Traefik Hello World example from docs: https://doc.traefik.io/traefik/getting-started/quick-start/
# This is fast! Router registers in <2 s
version: '3'

services:
  reverse-proxy:
    # The official v2 Traefik docker image
    image: traefik:v2.10
    # Enables the web UI and tells Traefik to listen to docker
    command: --api.insecure=true --providers.docker
    ports:
      # The HTTP port
      - "80:80"
      # The Web UI (enabled by --api.insecure=true)
      - "8080:8080"
    volumes:
      # So that Traefik can listen to the Docker events
      - /var/run/docker.sock:/var/run/docker.sock
      
  whoami:
    # A container that exposes an API to show its IP address
    image: traefik/whoami
    labels:
      - "traefik.http.routers.whoami.rule=Host(`whoami.docker.localhost`)"

docker-compose-slow.yml

# Minimal example using swarmmode
# This is SLOW! Router registers in 10-30 seconds
version: '3'

services:
  reverse-proxy:
    # The official v2 Traefik docker image
    image: traefik:v2.10
    # Enables the web UI and tells Traefik to listen to docker
    command:
      - --api.insecure=true
      - --providers.docker
      - --providers.docker.swarmmode=true
    ports:
      # The HTTP port
      - "80:80"
      # The Web UI (enabled by --api.insecure=true)
      - "8080:8080"
    volumes:
      # So that Traefik can listen to the Docker events
      - /var/run/docker.sock:/var/run/docker.sock

  whoami:
    # A container that exposes an API to show its IP address
    image: traefik/whoami
    deploy:
      labels:
        - "traefik.http.routers.whoami.rule=Host(`whoami.docker.localhost`)"
        - "traefik.http.services.whoami.loadbalancer.server.port=80"

instructions.sh

# Deploy to a docker swarm
docker stack deploy --compose-file docker-compose-slow.yml test-stack

# It can take 10-30s for the whoami router to register. Watch http://localhost:8080/dashboard/#/http/routers for changes. 

# If it does register quickly, rm the stack and recreate it 2-3 times to see the problem. 
docker stack rm test-stack