Dynamic haproxy using chef based on unprivileged containers (exposing containers port 80)

dynamic_haporxy.rb

template '/etc/haproxy/haproxy.cfg' do
  extend Helper
  variables(
    containers: container_ips('goatos'),
    start_port: 8000
   )
  source 'haproxy.cfg.erb'
end

haproxy.cfg.erb

global
        log /dev/log    local0
        log /dev/log    local1 notice
        chroot /var/lib/haproxy
        user haproxy
        group haproxy
        daemon

defaults
        log     global
        option  dontlognull
        contimeout 5000
        clitimeout 50000
        srvtimeout 50000
<% @containers.each |name, ip|%>
listen <%=name.upcase %> :<%= (@start_port+=1) %>
  mode http
  server <%= name %> <%= ip %>:<%= 80 %>
<% end %>

helper.rb

module Helper
  def container_ips
    data = {}
    user = Etc.getpwnam(name)
    config = File.join(user.dir, '.local/share/lxc') # this can be injected from outside as well
    LXC.list_containers(config_path: config).each do |n|
      ct = LXC::Container.new(n, config)
      if ct.running? and (not ct.ip_addresses.empty?)
        data[ct.name] = ct.ip_addresses.first
      end
    end
    data
  end
end