Container
https://hub.docker.com/_/haproxy

Configuration
/tmp/haproxy/haproxy.cfg

global
  maxconn 4096
  #stats timeout 30s
  #debug

defaults
  log global
  mode http
  option httplog
  option dontlognull
  timeout connect 5000
  timeout client 50000
  timeout server 50000
  log 127.0.0.1 local0
  #option httpchk

frontend frontend1
  bind :80
  mode http
  use_backend backend1

backend backend1
  mode http
  balance roundrobin
  option httpchk GET / HTTP/1.1
  http-check expect status 400
  server www1 172.17.0.2:80 check
  server www2 172.17.0.4:80 check
  server www3 172.17.0.6:80 check

listen stats 
  bind :9000
  mode http
  stats enable
  stats hide-version
  stats realm Haproxy\ Statistics
  stats refresh 60s
  stats show-node
  stats auth haproxy:password
  stats uri /

Deploy

docker run -d --name haproxy -v /tmp/haproxy:/usr/local/etc/haproxy:ro -p 8080:80 -p 9000:9000 haproxy:latest
docker logs -f  haproxy