docker-compose.yml

consul:
  image: progrium/consul
  name: consul
  ports:
    - "8500:8500"
    - "53:53/udp"
  command: -server -bootstrap -ui-dir /ui

registrator:
  image: progrium/registrator
  command: consul://consul:8500 --ttl 500
  volumes: 
    - /var/run/docker.sock:/tmp/docker.sock
  links:
    - consul:consul

haproxy:
  image: haproxy
  links:
    - rack1
    - rack2
  ports: 
    - 6379:6379
    - 8888:8888
  volumes:
    - ./haproxy.cfg:/usr/local/etc/haproxy/haproxy.cfg
  volumes_from:
    - consultemplate

rack1:
  name: rack1
  image: redis
  links: 
    - dynamo:dynamo
  ports:
    - 6379
  environment:
    - SERVICE_NAME=rack1

rack2:
  name: rack2
  image: redis
  links: 
    - dynamo:dynamo
  ports:
    - 6379
  environment:
    - SERVICE_NAME=rack2

consultemplate:
  name: consultemplate
  image: avthart/consul-template
  command: "consul-template -consul=$CONSUL_PORT_8500_TCP_ADDR:8500 -template /usr/local/etc/haproxy/haproxy.cfg.tmpl:/usr/local/etc/haproxy/haproxy.cfg -log-level=debug" 
  links:
    - consul:consul
  volumes:
    - ./:/usr/local/etc/haproxy/

dynamo:
  name: dynamo
  image: redis

How does haproxy know to restart when the template is changed?