meh

getconfigmd5.lua

-- A simple Lua script which serves up the HAProxy config md5
-- ubuntu install the lua-md5 package
-- ripped from https://github.com/mesosphere/marathon-lb/blob/master/getconfig.lua

md5 = require 'md5'

function read_config_file(cmdline)
  local found = false
  local filename = ''
  for s in string.gmatch(cmdline, '%g+') do
    if s == '-f' then
      found = true
    elseif found then
      filename = s
      break
    end
  end

  local f = io.open(filename, "rb")
  local config = f:read("*all")
  f:close()
  return config
end

function load_config()
  local f = io.open('/proc/self/cmdline', "rb")
  local cmdline = f:read("*all")
  f:close()
  return read_config_file(cmdline)
end

core.register_init(function()
  haproxy_config = load_config()
  haproxy_config_md5 = md5.sumhexa(haproxy_config)
end)

core.register_service("getconfigmd5", "http", function(applet)
  applet:set_status(200)
  applet:add_header("content-length", string.len(haproxy_config_md5))
  applet:add_header("content-type", "text/plain")
  applet:start_response()
  applet:send(haproxy_config_md5)
end)