gistfile1.txt

version: '3'
services:
  haproxy:
    image: haproxy:1.5
    volumes:
     - /path/to/haproxy.cfg:/usr/local/etc/haproxy/haproxy.cfg
    ports:
      - "80:80"

gistfile2.txt

global
  log 127.0.0.1 local0
  log 127.0.0.1 local1 notice

defaults
  log global
  mode http
  option httplog
  option dontlognull
  timeout connect 50000
  timeout client 100000
  timeout server 100000

frontend http-in
  bind 0.0.0.0:80
  mode http
  default_backend pheme_backends
  acl host_pheme hdr(host) -i pheme
  acl host_gatekeeper hdr(host) -i gatekeeper
  use_backend pheme_backends if host_pheme
  use_backend gatekeeper_backends if host_gatekeeper

backend pheme_backends
  mode http
  option forwardfor
  balance roundrobin
  server pheme pheme:80

backend gatekeeper_backends
  mode http
  option forwardfor
  balance roundrobin
  server gatekeeper gatekeeper:80