The ports allowing a docker swarm to communicate (to use only behind a firewall)

docker-swarm-ufw-ports

#!/bin/bash

ufw allow 2376/tcp
ufw allow 2377/tcp
ufw allow 7946
ufw allow 4789/udp

haproxy.cfg.template.erb

#
# Simple configuration for a TCP proxy
#
global
    daemon
    maxconn 256

resolvers dns
    nameserver public-0  127.0.0.11:53
    hold valid 5s

defaults
    mode tcp
    timeout connect 5000ms
    timeout client 50000ms
    timeout server 50000ms
    
<% @entries.each do |entry| %>
frontend in-<%= entry[:publicport] %>
    bind *:<%= entry[:publicport] %>
    default_backend out-<%= entry[:publicport] %>

backend out-<%= entry[:publicport] %>
    server server <%= entry[:privatehost] %>:<%= entry[:privateport] %>  maxconn 100  resolvers dns  init-addr libc,none  check
<% end %>

mc-dyn-router-generate.rb

#
# Generate configuration file using an array and a template
#
require 'erb'

class Config

  def initialize(configFile, templateFile)
      @configFile = configFile
      @template = ERB.new(File.read(templateFile))
  end
  
  def render
      @entries = []
      File.open(@configFile) { |f|
        f.readlines.each {|lines|
          entry = lines.split("\t")
          @entries << {
                          privatehost: entry[0].strip,
                          privateport: entry[1].strip,
                          publicport: entry[2].strip
                      }
        }
      }
      @template.result(binding())
  end
end

puts Config.new("rawconfig.txt","haproxy.cfg.template.erb").render